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Evolution is True! Get over it - Jerry Coyne Lecture
Jerry Allen Coyne (born December 30, 1949) is an American professor of biology, known for his work on speciation and his commentary on intelligent design. A prolific scientist and author, he has published dozens of papers elucidating the theory of evolution. He is currently a professor emeritus at the University of Chicago in the Department of Ecology and Evolution. His concentration is speciation and ecological and evolutionary genetics, particularly as they involve the fruit fly, Drosophila. He is the author of the text Speciation and the bestselling non-fiction book Why Evolution Is True.
https://www.youtube.com/watch?v=gCsabeaJHMI
How Paleontology Disproves Noah’s Flood
This is part of a series of videos explaining how different fields of study refute the Noachian deluge. This 3rd episode was done with assistance from my paleontologist friend, PaleoClipper as well as Steven Newton with the National Center for Science Education.
https://www.youtube.com/watch?v=VRXNJvWkkoI
9th Foundational Falsehood of Creationism
https://www.youtube.com/watch?v=Qfoje7jVJpU
Creationism and evolution tackled head-on in science lessons | Guardian Investigations
https://www.youtube.com/watch?v=Qr61zni_AxE
Scientific theory: A coherent group of propositions formulated to explain a group of facts or phenomena in the natural world and repeatedly confirmed through experiment or observation: e.g. The scientific theory of evolution.
http://www.dictionary.com/browse/scientific-theory
Science uses specialized terms that have different meanings than everyday usage. These definitions correspond to the way scientists typically use these terms in the context of their work. Note, especially, that the meaning of “theory” in science is different than the meaning of “theory” in everyday conversation.
Fact: In science, an observation that has been repeatedly confirmed and for all practical purposes is accepted as “true.” Truth in science, however, is never final and what is accepted as a fact today may be modified or even discarded tomorrow. Hypothesis: A tentative statement about the natural world leading to deductions that can be tested. If the deductions are verified, the hypothesis is provisionally corroborated. If the deductions are incorrect, the original hypothesis is proved false and must be abandoned or modified. Hypotheses can be used to build more complex inferences and explanations. Law: A descriptive generalization about how some aspect of the natural world behaves under stated circumstances. Theory: In science, a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.
https://ncse.com/library-resource/definitions-fact-theory-law-scientific-work
“Just a Theory”: 7 Misused Science Words Hypothesis. Theory. Law. These scientific words get bandied about regularly, yet the general public usually gets their meaning wrong.
“A word like ‘theory’ is a technical scientific term,” said Michael Fayer, a chemist at Stanford University. “The fact that many people understand its scientific meaning incorrectly does not mean we should stop using it. It means we need better scientific education.”
Just a theory?
Climate-change deniers and creationists have deployed the word “theory” to cast doubt on climate change and evolution.
“It’s as though it weren’t true because it’s just a theory,” Allain said.
That’s despite the fact that an overwhelming amount of evidence supports both human-caused climate change and Darwin’s theory of evolution.
Part of the problem is that the word “theory” means something very different in lay language than it does in science: A scientific theory is an explanation of some aspect of the natural world that has been substantiated through repeated experiments or testing. But to the average Jane or Joe, a theory is just an idea that lives in someone’s head, rather than an explanation rooted in experiment and testing.
https://www.scientificamerican.com/article/just-a-theory-7-misused-science-words/
A scientific theory is an explanation of an aspect of the natural world that can be repeatedly tested, in accordance with the scientific method, using a predefined protocol of observation and experiment.[1][2] Established scientific theories have withstood rigorous scrutiny and embody scientific knowledge.[3]
The definition of a scientific theory (often contracted to “theory” for the sake of brevity) as used in the disciplines of science is significantly different from the common vernacular usage of the word “theory”. In everyday speech, “theory” can imply that something is an unsubstantiated and speculative guess, the opposite of its meaning in science. These different usages are comparable to the opposing usages of “prediction” in science versus everyday speech, where it denotes a mere hope.
The strength of a scientific theory is related to the diversity of phenomena it can explain and its simplicity. As additional scientific evidence is gathered, a scientific theory may be modified and ultimately rejected if it cannot be made to fit the new findings; in such circumstances, a more accurate theory is then required. In certain cases, the less-accurate unmodified scientific theory can still be treated as a theory if it is useful (due to its sheer simplicity) as an approximation under specific conditions. A case in point is Newton’s laws of motion, which can serve as an approximation to special relativity at velocities that are small relative to the speed of light.
Scientific theories are testable and make falsifiable predictions.[5] They describe the causes of a particular natural phenomenon and are used to explain and predict aspects of the physical universe or specific areas of inquiry (for example, electricity, chemistry, and astronomy). Scientists use theories to further scientific knowledge, as well as to facilitate advances in technology or medicine.
As with other forms of scientific knowledge, scientific theories are both deductive and inductive, aiming for predictive and explanatory power.
The paleontologist Stephen Jay Gould wrote that “…facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world’s data. Theories are structures of ideas that explain and interpret facts.”
https://en.wikipedia.org/wiki/Scientific_theory
What Is a Scientific Theory?
“The way that scientists use the word ‘theory’ is a little different than how it is commonly used in the lay public,” said Jaime Tanner, a professor of biology at Marlboro College. “Most people use the word ‘theory’ to mean an idea or hunch that someone has, but in science the word ‘theory’ refers to the way that we interpret facts.”
The process of becoming a scientific theory Every scientific theory starts as a hypothesis. A scientific hypothesis is a suggested solution for an unexplained occurrence that doesn’t fit into a currently accepted scientific theory. In other words, according to the Merriam-Webster Dictionary, a hypothesis is an idea that hasn’t been proven yet. If enough evidence accumulates to support a hypothesis, it moves to the next step - known as a theory - in the scientific method and becomes accepted as a valid explanation of a phenomenon.
An important part of scientific theory includes statements that have observational consequences. A good theory, like Newton’s theory of gravity, has unity, which means it consists of a limited number of problem-solving strategies that can be applied to a wide range of scientific circumstances. Another feature of a good theory is that it formed from a number of hypotheses that can be tested independently.
A good example of the difference between a theory and a law is the case of Gregor Mendel. In his research, Mendel discovered that two separate genetic traits would appear independently of each other in different offspring. “Yet Mendel knew nothing of DNA or chromosomes. It wasn’t until a century later that scientists discovered DNA and chromosomes - the biochemical explanation of Mendel’s laws,” said Peter Coppinger, an associate professor of biology and biomedical engineering at the Rose-Hulman Institute of Technology. “It was only then that scientists, such as T.H. Morgan working with fruit flies, explained the Law of Independent Assortment using the theory of chromosomal inheritance. Still today, this is the universally accepted explanation (theory) for Mendel’s Law.”
https://www.livescience.com/21491-what-is-a-scientific-theory-definition-of-theory.html
Features of “Good” or Successful Theory A scientific theory must make testable or refutable predictions of what should happen or be seen under a given set of new, independent, observing or analysis circumstances from the particular problem or observation the theory was originally designed to explain.
We can use the construction of Darwinian histories of evolutionary theory to describe the emergence of a particular trait in any organism or the relationships among groups of organisms. Using the same problem-solving strategy, evolutionary theory can also “explain why we find contemporary organisms where we do by following the course of their historical modifications and migrations” (called “biogeography”, Kitcher p. 50). The problem-solving strategy can also be used to answer questions of extinctions in the fossil record or our historical records by showing how the extinct organism’s characteristics were no longer advantageous when the environment or competition changed.
Finally, a good or successful theory will also be fruitful in opening up new and profitable areas of research. Newton’s theories led to improvements in our understanding of hydrodynamics, chemistry, optics, electricity and magnetism, thermodynamics, etc. “A flourishing science is incomplete. A good theory should be productive; it should raise new questions and presume that those questions can be answered without giving up its problem-solving strategies” (Kitcher p. 48). There were many questions Darwin and his contemporaries had but they trusted that future scientists would answer them in ways “consistent with the presuppositions of Darwinian histories” (Kitcher p. 53). Genetics now explains how new characteristics arise in populations and are inherited. Population genetics explains how variations in characteristics are maintained and how certain characteristics can be fixed. Ecologists can answer what interactions among populations of organisms affect the survival and fruitfulness of characteristics.
http://www.astronomynotes.com/science-religion/NormLevan/s2-annot.htm
Can Science Ever Be “Settled”?
Gravitation. Evolution. The Big Bang. Germ Theory. Global Warming. They’re all scientific theories, and they’re all referred to as examples of “settled science” in various circles. Yet, is that even possible?
…
Science advances not merely by accepting the current best explanations as a foregone conclusion, but by testing them, probing them, pushing their limits and looking for gaps. But just because science is continuously challenging itself, assimilating new information, and revising its conclusions, doesn’t mean there aren’t many aspects that can be considered settled, at least at present.
…
The idea that the foundations of science can be shaken so easily by a surprising, reproducible observation or experiment is an important one, but it’s an important one only insofar as it helps separate science from non-science. (Or, if you prefer, pre-science.) At this stage in our understanding of the Universe, scientific revolutions must encompass the success of the previous theories that came before it, which is why general relativity includes Newtonian gravity, and which is why any viable candidate for a quantum theory of gravity must include general relativity (and all of its successful predictions) as a necessity.
When we say the science is settled, we don’t mean that we’ve stopped learning. In fact, we mean the exact opposite: that we have actually learned something valuable. “Settled science” isn’t the end of knowledge, it’s a mark that we’ve begun to legitimately understand something. But remember that the unsettling of settled science is always possible, and we must always keep our mind open to that possibility. If Earth’s gravity stopped working tomorrow and we all floated off into space, if animals began being born genetically identical to their parents, if the Universe began contracting, if germs were eradicated but the diseases they caused persisted, or if the next few years on Earth were a few degrees cooler globally, any one of these “settled” scientific facts would immediately cease to be so. Being “settled” doesn’t mean we’re 100% certain it’s correct, but it does mean that this is the best conclusion we can draw given what we know so far. And as what we know changes and grows, so does the breadth and depth of what “settled science” actually includes.
https://medium.com/starts-with-a-bang/can-science-ever-be-settled-433601c3580e
Should We Take Creation Stories in Genesis Literally?
Professor Dolansky specializes in Biblical Studies, with a focus on the history and religions of Israel and the ancient Near East and the development of the Hebrew Bible. Her research incorporates the tools of literary criticism, comparative religion, historical study, anthropology, archaeology, political science and classics in order to understand the worlds of the original authors and audiences of the biblical texts, and the subsequent development of Judaism and Christianity out of ancient Israelite religious beliefs and practices.
Creation stories in Genesis were among the many myths that were told in the ancient Near East. Today we may think of myths as beliefs that are not true, but as a literary genre, myths “are stories that convey and reinforce aspects of a culture’s worldview: many truths,” writes Dolansky. So to call something a myth-in this sense-does not necessarily imply that it is not true. Scholars argue that Biblical myths arose within the context of other ancient Near Eastern myths that sought to explain the creation of the world. Alongside Biblical myths were Mesopotamian myths in which, depending on the account, the creator was Enlil, Mami or Marduk. In ancient Egyptian mythology, the creator of the world was Atum in one creation story and Ptah in another.
“Like other ancient peoples, the Israelites told multiple creation stories,” writes Shawna Dolansky in her Biblical Views column. “The Bible gives us three (and who knows how many others were recounted but not preserved?). Genesis 1 differs from Genesis 2-3, and both diverge from a third version alluded to elsewhere in the Bible, a myth of the primordial battle between God and the forces of chaos known as Leviathan (e.g., Psalm 74), Rahab (Psalm 89) or the dragon (Isaiah 27; 51). This battle that preceded creation has the Mesopotamian Enuma Elish as its closest analogue. In Enuma Elish, the god Marduk defeats the chaotic waters in the form of the dragon Tiamat and recycles her corpse to create the earth.”
https://www.biblicalarchaeology.org/daily/biblical-topics/bible-interpretation/creation-stories-in-genesis/
Evolution/long ages contradicts Genesis order of Creation
Evolution postulates that the first living organism was a single cell, which arose from an oceanic primordial soup by chemical evolution.8 After that, living creatures evolved in the seas long before land plants and animals, and longer still before trees. But Genesis reveals that God created land plants, including trees, first.
Evolution teaches that ichthyosaurs and the other marine reptiles evolved from land reptiles, and that whales evolved from land mammals, which had evolved from other land reptiles. Day-agers dutifully claim that the former were created after the latter. Similarly, evolutionists believe that birds and pterosaurs evolved from land reptiles, while bats evolved from land mammals. However, Genesis explicitly teaches that God made the sea and flying creatures on Day 5, a day before He made land creatures, Day 6. This has led to very imaginative Scripture-twisting: that the eon-‘days’ were overlapping rather than sequential.9
Any sort of evolution must consistently deny a literal first solitary man and woman who are the sole ancestors of all other humans who ever existed.10 Rather, they say that a population of ape-like creatures evolved into a population of humans. Genesis on the other hand teaches that the first man was made not from living creatures but from inanimate matter (dust of the ground), which didn’t become living until God breathed upon it (Genesis 2:7). And the first woman likewise had no mother, but was made from the man’s rib (Genesis 2:21-24).
Day-age creationists fare little better than evolutionists, because they blindly accept the evolutionary dating. This ‘dates’ fossils of undoubted Homo sapiens at almost 200,000 years ago, far older than Adam could be, even with the most absurd stretching of the biblical timeline given in Genesis 5 and 11.11
https://creation.com/evolution-v-genesis-order
The Creation Order of Genesis
According to Genesis 1, after some preliminary firmament-creating and water-separating, on the third day God creates the Earth, and the first living things he places upon it are flowering plants. “And God said, Let the earth bring forth grass, the herb yielding seed, and the fruit tree yielding fruit after his kind, whose seed is in itself, upon the earth: and it was so.” (1:11)
But this is wrong. The first plants to appear on the Earth were not the flowering plants, which includes all true grasses and all plants that bear fruit which contains seeds (the scientific name for this group is angiosperms). On the contrary, the first angiosperms appear in the fossil record much later on, only 140 million years ago, during the time of the dinosaurs. For hundreds of millions of years before that, the Earth was dominated by other kinds of plants not mentioned in the Genesis account: mosses, ferns, and a different kind of plants, the gymnosperms, which do not bear seed-containing fruit and are represented today mainly by conifers and cycads.
On the fourth day, God creates the sun, moon and stars. I won’t belabor the point, but obviously the sun and other stars existed long before the Earth, and our moon predates all modern life. It would have to, since the prevailing hypothesis is that it was created by a gigantic impact that would have melted the Earth down to the crust, sterilizing any life that existed beforehand.
Next, on the fifth day, God creates all aquatic life (including the “great whales”) and all birds (“every winged fowl after his kind”). Again, this is wrong, and not just because the writer erroneously claims that Genesis depicts birds as appearing after land animals. Although fish did arise before land life, whales and dolphins are latecomers to the oceans. Like all mammals, they only arose after the dinosaurs had fallen, opening up new niches for other species to diversify into. The same is true of birds: they’re not as ancient a lineage as fish, but a new and late-arising branch on the tree of life, descended from one group of dinosaurs that survived the great K-T extinction 65 million years ago.
Finally, on the sixth day, God creates land animals, insects (“every thing that creepeth upon the earth”), and human beings. This, too, is wrong in several ways. Unlike birds and whales, insects are truly an ancient lineage: the earliest known insect fossil is about 400 million years old, and the oldest insects of all are likely even earlier. And of course, “land animals” is a huge group, many species of which predate human beings by enormous time intervals (particularly if we take this group to include dinosaurs, as the creationists do).
Far from paralleling the geologic record, the Genesis story gets it wrong on every detail. If the creation order of Genesis followed the order of appearance of major groups of multicellular life, it would have begun with simple, non-vascular plants like moss and algae, followed by fish and insects, then amphibians, then reptiles, then mammals and flowering plants, birds, whales, and finally human beings.
http://bigthink.com/daylight-atheism/the-creation-order-of-genesis
Genetic Evidence
Through news accounts and crime stories, we’re all familiar with the fact that the DNA in our cells reflects each individual’s unique identity and how closely related we are to one another. The same is true for the relationships among organisms. DNA, or deoxyribonucleic acid, is the molecule that makes up an organism’s genome in the nucleus of every cell. It consists of genes, which are the molecular codes for proteins - the building blocks of our tissues and their functions. It also consists of the molecular codes that regulate the output of genes - that is, the timing and degree of protein-making. DNA shapes how an organism grows up and the physiology of its blood, bone, and brains.
DNA is thus especially important in the study of evolution. The amount of difference in DNA is a test of the difference between one species and another - and thus how closely or distantly related they are.
While the genetic difference between individual humans today is minuscule - about 0.1%, on average - study of the same aspects of the chimpanzee genome indicates a difference of about 1.2%. The bonobo (Pan paniscus), which is the close cousin of chimpanzees (Pan troglodytes), differs from humans to the same degree. The DNA difference with gorillas, another of the African apes, is about 1.6%. Most importantly, chimpanzees, bonobos, and humans all show this same amount of difference from gorillas. A difference of 3.1% distinguishes us and the African apes from the Asian great ape, the orangutan. How do the monkeys stack up? All of the great apes and humans differ from rhesus monkeys, for example, by about 7% in their DNA.
Geneticists have come up with a variety of ways of calculating the percentages, which give different impressions about how similar chimpanzees and humans are. The 1.2% chimp-human distinction, for example, involves a measurement of only substitutions in the base building blocks of those genes that chimpanzees and humans share. A comparison of the entire genome, however, indicates that segments of DNA have also been deleted, duplicated over and over, or inserted from one part of the genome into another. When these differences are counted, there is an additional 4 to 5% distinction between the human and chimpanzee genomes.
No matter how the calculation is done, the big point still holds: humans, chimpanzees, and bonobos are more closely related to one another than either is to gorillas or any other primate. From the perspective of this powerful test of biological kinship, humans are not only related to the great apes - we are one. The DNA evidence leaves us with one of the greatest surprises in biology: the wall between human, on the one hand, and ape or animal, on the other, has been breached. The human evolutionary tree is embedded within the great apes.
The strong similarities between humans and the African great apes led Charles Darwin in 1871 to predict that Africa was the likely place where the human lineage branched off from other animals - that is, the place where the common ancestor of chimpanzees, humans, and gorillas once lived. The DNA evidence shows an amazing confirmation of this daring prediction. The African great apes, including humans, have a closer kinship bond with one another than the African apes have with orangutans or other primates. Hardly ever has a scientific prediction so bold, so ‘out there’ for its time, been upheld as the one made in 1871 - that human evolution began in Africa.
The DNA evidence informs this conclusion, and the fossils do, too. Even though Europe and Asia were scoured for early human fossils long before Africa was even thought of, ongoing fossil discoveries confirm that the first 4 million years or so of human evolutionary history took place exclusively on the African continent. It is there that the search continues for fossils at or near the branching point of the chimpanzee and human lineages from our last common ancestor.
Primate Family Tree Due to billions of years of evolution, humans share genes with all living organisms. The percentage of genes or DNA that organisms share records their similarities. We share more genes with organisms that are more closely related to us.
Humans belong to the biological group known as Primates, and are classified with the great apes, one of the major groups of the primate evolutionary tree. Besides similarities in anatomy and behavior, our close biological kinship with other primate species is indicated by DNA evidence. It confirms that our closest living biological relatives are chimpanzees and bonobos, with whom we share many traits. But we did not evolve directly from any primates living today.
DNA also shows that our species and chimpanzees diverged from a common ancestor species that lived between 8 and 6 million years ago. The last common ancestor of monkeys and apes lived about 25 million years ago.
http://humanorigins.si.edu/evidence/genetics
One of the strongest evidences for common descent comes from the study of gene sequences. Comparative sequence analysis examines the relationship between the DNA sequences of different species, producing several lines of evidence that confirm Darwin’s original hypothesis of common descent. If the hypothesis of common descent is true, then species that share a common ancestor inherited that ancestor’s DNA sequence, as well as mutations unique to that ancestor. More closely related species have a greater fraction of identical sequence and shared substitutions compared to more distantly related species.
The simplest and most powerful evidence is provided by phylogenetic reconstruction. Such reconstructions, especially when done using slowly evolving protein sequences, are often quite robust and can be used to reconstruct a great deal of the evolutionary history of modern organisms (and even in some instances such as the recovered gene sequences of mammoths, Neanderthals or T. rex, the evolutionary history of extinct organisms). These reconstructed phylogenies recapitulate the relationships established through morphological and biochemical studies. The most detailed reconstructions have been performed on the basis of the mitochondrial genomes shared by all eukaryotic organisms, which are short and easy to sequence; the broadest reconstructions have been performed either using the sequences of a few very ancient proteins or by using ribosomal RNA sequence.
Phylogenetic relationships also extend to a wide variety of nonfunctional sequence elements, including repeats, transposons, pseudogenes, and mutations in protein-coding sequences that do not result in changes in amino-acid sequence. While a minority of these elements might later be found to harbor function, in aggregate they demonstrate that identity must be the product of common descent rather than common function.
Comparison of the DNA sequences allows organisms to be grouped by sequence similarity, and the resulting phylogenetic trees are typically congruent with traditional taxonomy, and are often used to strengthen or correct taxonomic classifications. Sequence comparison is considered a measure robust enough to correct erroneous assumptions in the phylogenetic tree in instances where other evidence is scarce. For example, neutral human DNA sequences are approximately 1.2% divergent (based on substitutions) from those of their nearest genetic relative, the chimpanzee, 1.6% from gorillas, and 6.6% from baboons. Genetic sequence evidence thus allows inference and quantification of genetic relatedness between humans and other apes. The sequence of the 16S ribosomal RNA gene, a vital gene encoding a part of the ribosome, was used to find the broad phylogenetic relationships between all extant life. The analysis, originally done by Carl Woese, resulted in the three-domain system, arguing for two major splits in the early evolution of life. The first split led to modern Bacteria and the subsequent split led to modern Archaea and Eukaryotes.
Endogenous retroviruses (or ERVs) are remnant sequences in the genome left from ancient viral infections in an organism. The retroviruses (or virogenes) are always passed on to the next generation of that organism that received the infection. This leaves the virogene left in the genome. Because this event is rare and random, finding identical chromosomal positions of a virogene in two different species suggests common ancestry.
http://www.darwinwasright.org/dna_sequencing.html
The proteomic evidence also supports the universal ancestry of life. Vital proteins, such as the ribosome, DNA polymerase, and RNA polymerase, are found in everything from the most primitive bacteria to the most complex mammals. The core part of the protein is conserved across all lineages of life, serving similar functions. Higher organisms have evolved additional protein subunits, largely affecting the regulation and protein-protein interaction of the core. Other overarching similarities between all lineages of extant organisms, such as DNA, RNA, amino acids, and the lipid bilayer, give support to the theory of common descent. Phylogenetic analyses of protein sequences from various organisms produce similar trees of relationship between all organisms. The chirality of DNA, RNA, and amino acids is conserved across all known life. As there is no functional advantage to right- or left-handed molecular chirality, the simplest hypothesis is that the choice was made randomly by early organisms and passed on to all extant life through common descent. Further evidence for reconstructing ancestral lineages comes from junk DNA such as pseudogenes, “dead” genes that steadily accumulate mutations.
What do modern DNA studies tell us about evolution?
The explosion of genome sequences and DNA data banks in recent years has provided an enormous storehouse of data for biologists. Analyses of these data have dramatically confirmed the central tenets of evolution, including the common ancestry of all biological organisms, all arranged convincingly in a phylogenetic family tree, in most cases exactly as had been previously reckoned based solely on similarities of physical forms and biological functions. As anthropologist Alan R. Rogers recently noted, “Phylogenetic pattern is everywhere in nature. It makes sense only if all living things evolved from a single ancestor.” [Rogers2011, pg. 31]. Sean Carroll adds that DNA evidence “clinches the case for biological evolution as the basis for life’s diversity, beyond any reasonable doubt” [Carroll2006, pg. 17]. Similarly, geneticist Daniel J. Fairbanks emphasizes that [Fairbanks2007, pg. 170]:
[The] obvious hierarchical arrangement of life, and the literally millions of ancestral relics in our DNA – all undeniably attest to our common evolutionary origin with the rest of life. If someone can believe that all living organisms share the same creator, why not consider that all living organisms share a common genetic heritage?
http://www.sciencemeetsreligion.org/evolution/dna.php
How Did Life Arise on Earth?
Earth is estimated to be about 4.5 billion years old, and for much of that history it has been home to life in one weird form or another.
Indeed, some scientists think life appeared the moment our planet’s environment was stable enough to support it.
The earliest evidence for life on Earth comes from fossilized mats of cyanobacteria called stromatolites in Greenland that are about 3.7 billion years old. Ancient as their origins are, these bacteria (which are still around today) are already biologically complex-they have cell walls protecting their protein-producing DNA, so scientists think life must have begun much earlier. In fact, there are hints of life in even more primeval rocks: 4.1-billion-year-old zircons from Western Australia contain high amounts of a form of carbon typically used in biological processes.
But despite knowing approximately when life first appeared on Earth, scientists are still far from answering how it appeared.
“Many theories of the origin of life have been proposed, but since it’s hard to prove or disprove them, no fully accepted theory exists,” said Diana Northup, a cave biologist at the University of New Mexico.
The answer to this question would not only fill one of the largest gaps in scientists’ understanding of nature, but also would have important implications for the likelihood of finding life elsewhere in the universe.
https://www.livescience.com/1804-greatest-mysteries-life-arise-earth.html
The End of the RNA World Is Near, Biochemists Argue
Four billion years ago, the first molecular precursors to life emerged, swirling about in Earth’s primordial soup of chemicals. Although the identity of these molecules remains a subject of fractious debate, scientists agree that the molecules would have had to perform two major functions: storing information and catalyzing chemical reactions. The modern cell assigns these responsibilities to its DNA and its proteins, respectively - but according to the narrative that dominates origin-of-life research and biology-textbook descriptions today, RNA was the first to play that role, paving the way for DNA and proteins to take over later.
This hypothesis, proposed in the 1960s and dubbed the “RNA world” two decades later, is usually viewed as the most likely explanation for how life got its start. That’s mainly because, theorizing aside, the RNA world is fortified by much more experimental evidence than any of its competitors have accumulated. Last month, Quanta Magazine reported on an alternative theory suggesting that protein-like molecules, rather than RNA, may have been the planet’s first self-replicators. But its findings were purely computational; the researchers have only just begun experiments to seek support for their claims.
Now, a pair of researchers has put forth another theory - this time involving the coevolution of RNA and peptides - that they hope will shake the RNA world’s hold.
In their recent papers, Carter and Wills show that their peptide-RNA world solves gaps in origin-of-life history that RNA alone can’t explain. “They provide solid theoretical and experimental evidence that peptides and RNA were jointly involved in the origin of the genetic code right from the start,” Hofmeyr said, “and that metabolism, construction through transcription and translation, and replication must have coevolved.”
Of course, the Carter-Wills model begins with the genetic code, the existence of which presupposes complex chemical reactions involving molecules like transfer RNA and the loading enzymes. The researchers claim that the events leading up to their proposed scenario involved RNA and peptides interacting (in the complex that Carter described in the 1970s, for example). Yet that suggestion still leaves many open questions about how that chemistry began and what it looked like.
To answer these questions, theories abound that move far beyond the RNA world. In fact, some scientists take an approach precisely opposite to that of Carter and Wills: They think instead that the earliest stages of life did not need to begin with anything resembling the kind of chemistry seen today. Doron Lancet, a genomics researcher at the Weizmann Institute of Science in Israel, posits an alternative theory that rests on assemblies of lipids that catalyze the entrance and exit of various molecules. Information is carried not by genetic sequences, but rather by the lipid composition of such assemblies.
Just like the model proposed by Carter and Wills, Lancet’s ideas involve not one type of molecule but a huge variety of them. “More and more bits of evidence are accumulating,” Lancet said, “that can make an alternative hypothesis be right.” The jury is still out on what actually transpired at life’s origins, but the tide seems to be turning away from a story dedicated solely to RNA.
“We should put only a few of our eggs in the RNA world basket,” Hofmeyr said.
https://www.quantamagazine.org/the-end-of-the-rna-world-is-near-biochemists-argue-20171219/
Dear Science: How do we know how old the Earth is?
Scientists now know the Earth is actually 4.54 billion years old, an age built on many lines of evidence from the geologic record.
The modern effort to understand the age of the planet started with Nicholas Steno, a Danish anatomist and geologist who was among the first to realize that fossils are the remains of living creatures. He proposed that geologists might learn about Earth’s history by sifting through layers of rock, which were laid down over the course of millennia and provide a backward chronology of our planet.
A century later, William Smith realized that rock layers at distant locations came from the same time period. He created a catalogue of strata (which all got colorful names such as Lias Blue, and Ditto White) and argued that each one represented a distinct time in Earth’s history - a principle known as fossil succession.
The accumulating evidence pointed to an extraordinary new idea: that the history of Earth goes back much, much further than any human memory. In 1788, Scottish geologist James Hutton published his “Theory of Earth,” which introduced the world to the idea of “deep time.” The implications of the treatise were revolutionary: Not only was the Earth not young, but it was not static, Hutton said. The same geologic forces that operate today, like deposition, erosion and uplift, have been shaping the Earth for ages with “no vestige of a beginning, no prospect of an end.”
Science provided a new way of thinking about Earth’s history; it made the distant past knowable. Rather than assume the planet was the product of bygone catastrophes, such as a massive global flood, scientists could explain the ancient rock record with phenomena that exist today.
This spawned several earnest - if not entirely successful - attempts to determine the age of the Earth based on ongoing natural processes. One calculated how long it would take rivers to deliver enough dissolved minerals to the ocean to give it its current saltiness (answer: 90 million to 100 million years). Others looked at the average rate of sedimentation and concluded it would take anywhere from 3 million to 1.6 billion years for the rock record to reach its current thickness.
But the big breakthrough came with the invention of radiometric dating. Shortly after radioactivity was discovered in 1896, scientists realized they could figure out how old a rock was by measuring how much of the uranium in it had decayed into lead.
Here’s how that works: The nuclei of radioactive elements decay - or spontaneously break down - at predictable rates. For example, half of a given batch of uranium will decay into lead every 710 million to 4.47 billion years, depending on the isotope used (this number is termed the element’s “half-life”). That uranium, which was created during a supernova that occurred long before our solar system existed, lingers in trace amounts within the Earth. When a rock is formed in the bowels of the planet, uranium atoms are trapped within it. These atoms will decay as the rock ages, and by measuring the ratio of radioactive isotopes within the rock, scientists can figure out how long it has been around.
https://www.washingtonpost.com/news/speaking-of-science/wp/2017/03/06/dear-science-how-do-we-know-how-old-the-earth-is/?utm_term=.e606ee05589b
The Earth is very old. But how old, exactly? And how can we know with any degree of confidence? As Henry Reich describes in the video above, the process of scientifically estimating the age of the Earth revolves around, essentially, finding the oldest piece of the planet we can, then figuring out how old that piece is.
Finding super old rocks is conceptually straightforward, but practically difficult. The processes of plate tectonics mean that the Earth is constantly recycling its rock, breaking it down into magma in the interior before pumping it back up to the surface once more. But old rocks do exist, says Reich, and the oldest rock we know is a tiny piece of zircon found in western Australia.
The process of figuring out a rock’s age often falls to the scientific techniques of radiometric dating, the most famous of which is radiocarbon dating. This process focuses on the ratio between the number of carbon-14 and carbon-12 isotopes in any once-living being: that ratio indicates how long it’s been since that being was alive. But carbon is not the only element that can be dated-a whole host of others exist. In uranium-lead dating, for instance, the radioactive decay of uranium into lead proceeds at a reliable rate.
Based on the very old zircon rock from Australia we know that the Earth is at least 4.374 billion years old. But it could certainly be older. Scientists tend to agree that our little planet is around 4.54 billion years old-give or take a few hundred million.
https://www.smithsonianmag.com/smart-news/how-do-we-know-earth-46-billion-years-old-180951483/
How Science Figured Out the Age of Earth For centuries scholars sought to determine Earth’s age, but the answer had to wait for careful geologic observation, isotopic analyses of the elements and an understanding of radioactive decay.
By the late 19th century the geologists included here had reached a consensus for the age of the earth of around 100 million years. Having come that far, they were initially quite reluctant to accept a further expansion of the geologic timescale by a factor of 10 or more. And we should resist the temptation to blame them for their resistance. Radioactivity was poorly understood. Different methods of measurement (such as the decay of uranium to helium versus its decay to lead) sometimes gave discordant values, and almost a decade passed between the first use of radiometric dating and the discovery of isotopes, let alone the working out of the three separate major decay chains in nature. The constancy of radioactive decay rates was regarded as an independent and questionable assumption because it was not known-and could not be known until the development of modern quantum mechanics-that these rates were fixed by the fundamental constants of physics.
https://www.scientificamerican.com/article/how-science-figured-out-the-age-of-the-earth/
How Do We Know The Earth Is 4.5 Billion Years Old?
You don’t trust radiometric dating? Fine. Buy a magnifying class and a box of Twinkies and visit a dendro lab. Tree rings form a unique fingerprint as trees across a region are exposed to similar conditions. For this reason, overlapping ring patterns from living, dead, and fossilized trees can be lined up to build continuous series stretching back through thousands and thousands of years. 12,000 and counting. No fancy science required.
Easier are simple geologic strata:
This is the Grand Canyon:
Those lines are sedimentation lines that form 40 major layers spanning 2 billion years of deposition. Okay, you might need a degree in geology to tell desert sand deposition from silt and to follow the series around the West to account for disconformities, but even a casual, unbiased evaluation will convince you utterly of two things: 1) The canyon was laid down by erosion through ancient sediments, not cut by any flood, and 2) those sediments were laid down over many, many, many millions of years.
https://www.forbes.com/sites/quora/2017/02/07/how-do-we-know-the-earth-is-4-5-billion-years-old/#498b629a9255
Oldest ice core: Finding a 1.5 million-year record of Earth’s climate
How far into the past can ice-core records go? Scientists have now identified regions in Antarctica they say could store information about Earth’s climate and greenhouse gases extending as far back as 1.5 million years, almost twice as old as the oldest ice core drilled to date.
The results are published today in Climate of the Past, an open-access journal of the European Geosciences Union (EGU).
By studying the past climate, scientists can understand better how temperature responds to changes in greenhouse-gas concentrations in the atmosphere. This, in turn, allows them to make better predictions about how climate will change in the future.
“Ice cores contain little air bubbles and, thus, represent the only direct archive of the composition of the past atmosphere,” says Hubertus Fischer, an experimental climate physics professor at the University of Bern in Switzerland and lead author of the study. A 3.2-km-long ice core drilled almost a decade ago at Dome Concordia (Dome C) in Antarctica revealed 800,000 years of climate history, showing that greenhouse gases and temperature have mostly moved in lockstep.
https://www.sciencedaily.com/releases/2013/11/131105081228.htm
Paleoclimatology: The Ice Core Record To pry climate clues out of the ice, scientists began to drill long cores out of the ice sheets in Greenland and Antarctica in the late 1960s. By the time Alley and the GISP2 project finished in the early 1990s, they had pulled a nearly 2-mile-long core (3,053.44 meters) from the Greenland ice sheet, providing a record of at least the past 110,000 years. Even older records going back about 750,000 years have come out of Antarctica. Scientists have also taken cores from thick mountain glaciers in places such as the Andes Mountains in Peru and Bolivia, Mount Kilimanjaro in Tanzania, and the Himalayas in Asia.
The ice cores can provide an annual record of temperature, precipitation, atmospheric composition, volcanic activity, and wind patterns. In a general sense, the thickness of each annual layer tells how much snow accumulated at that location during the year. Differences in cores taken from the same area can reveal local wind patterns by showing where the snow drifted. More importantly, the make-up of the snow itself can tell scientists about past temperatures. As with marine fossils, the ratio of oxygen isotopes in the snow reveals temperature, though in this case, the ratio tells how cold the air was at the time the snow fell. In snow, colder temperatures result in higher concentrations of light oxygen.
Scientists can confirm these chemistry-based temperature measurements by observing the temperature of the ice sheet directly. The ice sheet’s thickness makes its temperature much more resistant to change than the six inches of snow that might fall on your driveway during a winter snowstorm. As Alley explained to the Earth Observatory, the ice sheet can be compared to a frozen roast that is put directly into the oven. The outside heats up quickly, but the center remains cold, close to the temperature of the freezer, for a long time. Similarly, the ice sheet has warmed somewhat since the Ice Age, but not completely. The top has warmed as global temperatures have warmed, while the bottom has been warmed by heat flow from deep inside the Earth. But in the middle of an ice sheet, the ice remains close to the Ice Age temperatures at which it formed. “Because we understand how heat moves in ice, [and] we know how cold the ice is today, we can calculate how cold the ice was during the Ice Age,” says Alley.
Finally, anything that settles on the ice tends to remain fixed in the layer it landed on. Of particular interest are wind-blown dust and volcanic ash. As with dust found in sea sediments, dust in ice can be analyzed chemically to find out where it came from. The amount and location of dust tells scientists about wind patterns and strength at the time the particles were deposited. Volcanic ash can also indicate wind patterns. Additionally, volcanoes pump sulfates into the atmosphere, and these tiny particles also end up in the ice cores. This evidence is important because volcanic activity can contribute to climate change, and the ash layers can often be dated to help calibrate the timeline in the layers of ice.
Though ice cores have proven to be one of the most valuable climate records to date, they only provide direct evidence about temperature and rainfall where ice still exists, though they hint at global conditions. Marine sediment cores cover a broader area-nearly 70 percent of the Earth is covered in oceans-but they only give tiny hints about the climate over the land. Soil and rocks on the Earth’s surface reveal the advance and retreat of glaciers over the land surface, and fossilized pollen traces out rough boundaries of where the climate conditions were right for different species of plants and trees to live. Unique water and rock formations in caves harbor a climate record of their own. To understand the Earth’s climate history, scientists must bring together all of these scattered threads into a single, seamless story.
https://earthobservatory.nasa.gov/Features/Paleoclimatology_IceCores/
Record ice core reveals Earth’s ancient atmosphere
The longest ice-core record of climate history ever obtained has hugely extended the detailed history of Earth’s atmosphere, and shows that levels of greenhouse gases really do march in lockstep with changes in temperature.
The frozen record of the Earth’s atmosphere is 3270 metres long and covers the last 650,000 years - 50% longer than before. It was obtained from the tiny air bubbles trapped in a deep ice core from Antarctica.
The tight coupling between temperatures and the greenhouse gas levels revealed by the core matches the predictions from climate models used to forecast future global warming. It also bears some good news: the warm interglacial periods between ice ages can last a long time, contrary to the view that we may already be due for the onset of the next ice age.
The European Project for Ice Coring in Antarctica (EPICA) team has spent years drilling the ice core in Antarctica’s Ice Dome Concordia. They had previously analysed its record of global temperatures, but have just completed the detailed analysis of the trapped air. The bubbles record how the planet’s atmosphere changed over six ice ages and the warmer periods in between. But during all that time, the atmosphere has never had anywhere near the levels of greenhouse gases seen today.
Today’s level of 380 parts per million of carbon dioxide is 27% above its previous peaks of about 300 ppm, according to the team led by Thomas Stocker of the University of Bern in Switzerland.
Validation and refinement Edward Brook, an ice-core researcher at Oregon State University, US, who was not involved in the project, told New Scientist that the good match between climate model behaviour and the ice core data “really validates” the models’ predictions of what should happen as greenhouse gas levels increase. The precise new data in addition provides baselines that can be used to further refine climate models, Brook says.
The data also show that half of the previous six interglacial periods each lasted nearly 30,000 years - far longer than the roughly 10,000 years of the most recent cycles. The current interglacial period has persisted for about 10,000 years so far.
In the future, it should be possible to push the record even further back. The ice core dates back to 890,000 years ago but has yet to be analysed.
https://www.newscientist.com/article/dn8369-record-ice-core-reveals-earths-ancient-atmosphere/
When and how did plate tectonics begin on Earth?
Little Isotopes, Big Clues
One of the challenges with studying the onset of plate tectonics is that the rock record from the Earth’s early years is very sparse. “There’s just not much to work with,” van Hunen says. Very little rock remains that’s older than 3 billion years, he says, “and anything you find will be very highly deformed. We can look for structures associated with plate tectonics today, such as [those created in] subduction zones or mountain ranges, but they’re almost impossible to recognize in Archean rocks, since all we have are tiny patches that are highly metamorphosed.”
Instead of relying on macroscopic clues found in rocks, scientists are turning to the atomic scale, using isotope geochemistry. “Geochemistry can tell us a lot about the deep past,” van Hunen says. “Even in the tiniest rock, the chemistry will be intact.” Over the last few years, researchers have refined several isotopic tools that may serve as geochemical fingerprints of ancient plate tectonic processes.
Geochemists use two types of isotopes to study the history of rocks and minerals: stable and radiogenic. Stable isotopes occur in different ratios in different geological settings (such as in the mantle versus the crust), so these isotopes, such as oxygen-18 and oxygen-16, can be used to determine where different magmas originated.
Radiogenic, or parent-daughter isotope pairs, such as uranium and lead, rubidium and strontium, samarium and neodymium, and lutetium and hafnium, decay at specific rates and can be used to evaluate the timing of geological processes, such as when the continents formed. These isotopes also fractionate differently in different magmatic settings so they can also be used to decipher the processes involved in magma generation and answer questions about how rocks - and continents - formed.
Isotope geochemistry may address one of the biggest mysteries surrounding the onset of plate tectonics: when and how continental crust began forming. “Isotopes of oxygen, hafnium and uranium-lead measured in the mineral zircon can tell us about the formation of new crust from the mantle and the timing of reworking of continental crust during orogenic [collision, mountain-building] events,” says Bruno Dhuime, a geochemist at the University of Bristol in England. For example, in a 2014 study in Nature Geoscience, researchers used isotopes of uranium and lead preserved in zircon crystals found in ancient rocks in Western Australia to confirm the age of the oldest known continental crust to 4.4 billion years old - indicating that continental crust started forming only 100 million years after Earth’s formation, long before the onset of plate tectonics.
The bulk of continental crust is thought to have formed prior to plate tectonics starting on Earth. Some researchers suggest that the continental crust could have formed by mantle plume-like volcanism. Evidence for this early crustal formation comes from isotopic signatures preserved when certain elements diffused into the liquid magma when melting occured in the mantle. Credit: K. Canter, AGI.The bulk of continental crust is thought to have formed prior to plate tectonics starting on Earth. Some researchers suggest that the continental crust could have formed by mantle plume-like volcanism. Evidence for this early crustal formation comes from isotopic signatures preserved when certain elements diffused into the liquid magma when melting occured in the mantle. Credit: K. Canter, AGI.
The bulk of continental crust is thought to have formed prior to plate tectonics starting on Earth. Some researchers suggest that the continental crust could have formed by mantle plume-like volcanism. Evidence for this early crustal formation comes from isotopic signatures preserved when certain elements diffused into the liquid magma when melting occured in the mantle. Credit: K. Canter, AGI.
And in a 2012 study in Science, Dhuime and his group looked at ratios of these different isotopes collected in a worldwide database of more than 7,000 zircons to model the volume of continental crust through time. Their research indicates that the overall balance of continental crust - crust added from the mantle minus recycled material back into the mantle - has been more or less constant throughout most of Earth’s history. That suggests, Dhuime says, that plate tectonics has operated more or less continuously since it began, without any interruptions that might have thrown off the equilibrium between the creation of new crust and the destruction of old crust.
As to when it began, further isotopic research has shown that something big began to happen about 3 billion years ago - perhaps the onset of plate tectonics. Using rubidium-strontium ratios in more than 13,000 samples of rock ranging in age from the Hadean to the Phanerozoic, Dhuime and his colleagues found “that the juvenile [continental] crust had a low silica content and was largely mafic in composition [closer to basaltic and made up of dark-colored minerals such as olivine] during the first 1.5 billion years of Earth’s evolution, consistent with magmatism on a pre-plate tectonics planet,” the team wrote in Nature Geoscience in June 2015. “About 3 billion years ago, the rubidium-strontium ratios of the juvenile continental crust increased, indicating that the newly formed crust became more silica-rich and probably thicker,” they wrote.
Rubidium decays to strontium with a long half-life of nearly 49 billion years, making it an ideal tool for studying conditions on early Earth. When mantle material melts to form new crust, rubidium preferentially migrates into granitic melt more so than strontium, so the more felsic (granitic) the crust, the higher the rubidium-strontium ratio will be in that crust. By tabulating rubidium-strontium ratios for those 13,000 samples, Dhuime and colleagues showed that these particular isotopes can be used as proxies for the silica content, which is a known marker for the thickness and volume of early continental crust.
The combination of oxygen, hafnium and uranium-lead isotopes in zircon indicates a change in the volume of crust about 3 billion years ago, which Dhuime and his colleagues say may be related to increased recycling associated with the onset of plate tectonics. In summary, the isotopic clues suggest that continental crust started forming 4.4 billion years ago, formed at a relatively constant rate until 3 billion years ago, then plate tectonics started and began recycling crust at the same rate as new crust was being made, creating a balance that has remained steady to modern day.
https://www.earthmagazine.org/article/when-and-how-did-plate-tectonics-begin-earth
Facts About Pangaea, Ancient Supercontinent
History More than a century ago, the scientist Alfred Wegener proposed the notion of an ancient supercontinent, which he named Pangaea (sometimes spelled Pangea), after putting together several lines of evidence.
The first and most obvious was that the “continents fit together like a tongue and groove,” something that was quite noticeable on any accurate map, Murphy said. Another telltale hint that Earth’s continents were all one land mass comes from the geologic record. Coal deposits found in Pennsylvania have a similar composition to those spanning across Poland, Great Britain and Germany from the same time period. That indicates that North America and Europe must have once been a single landmass. And the orientation of magnetic minerals in geologic sediments reveals how Earth’s magnetic poles migrated over geologic time, Murphy said.
In the fossil record, identical plants, such as the extinct seed fern Glossopteris, are found on now widely disparate continents. And mountain chains that now lie on different continents, such as the Appalachians in the United States and the Atlas Mountains in Morocco, were all part of the Central Pangaea Mountains, formed through the collision of the supercontinents Gondwana and Laurussia.
Pangaea formed through a gradual process spanning a few hundred million years. Beginning about 480 million years ago, a continent called Laurentia, which includes parts of North America, merged with several other micro-continents to form Euramerica. Euramerica eventually collided with Gondwana, another supercontinent that included Africa, Australia, South America and the Indian subcontinent.
About 200 million years ago, the supercontinent began to break up. Gondwana (what is now Africa, South America, Antarctica, India and Australia) first split from Laurasia (Eurasia and North America). Then about 150 million years ago, Gondwana broke up. India peeled off from Antarctica, and Africa and South America rifted, according to a 1970 article in the Journal of Geophysical Research. Around 60 million years ago, North America split off from Eurasia.
Life and climate Having one massive landmass would have made for very different climactic cycles. For instance, the interior of the continent may have utterly dry, as it was locked behind massive mountain chains that blocked all moisture or rainfall, Murphy said.
But the coal deposits found in the United States and Europe reveal that parts of the ancient supercontinent near the equator must have been a lush, tropical rainforest, similar to the Amazonian jungle, Murphy said. (Coal forms when dead plants and animals sink into swampy water, where pressure and water transform the material into peat, then coal.)
“The coal deposits are essentially telling us that there was plentiful life on land,” Murphy told Live Science.
Pangaea existed for 100 million years, and during that time period several animals flourished, including the Traversodontidae, a family of plant-eating animals that includes the ancestors of mammals.
During the Permian period, insects such as beetles and dragonflies flourished. But the existence of Pangaea overlapped with the worst mass extinction in history, the Permian-Triassic (P-TR) extinction event. Also called the Great Dying, it occurred around 252 million years ago and caused most species on Earth to go extinct. The early Triassic period saw the rise of archosaurs, a group of animals that eventually gave rise to crocodiles and birds, and a plethora of reptiles. And about 230 million years ago some of the earliest dinosaurs emerged on Pangaea, including theropods, largely carnivorous dinosaurs that mostly had air-filled bones and feathers similar to birds.
https://www.livescience.com/38218-facts-about-pangaea.html
Scientists have used groundbreaking technology to figure out how the Earth looked a billion years ago
The story of plate tectonics goes back to 1912, when a German atmospheric physicist, Alfred Wegener, looked at a map and noticed that the opposing coastlines of Africa and South America seemed oddly congruent, like matching pieces of a jigsaw puzzle. Other geologists had remarked similarly, and in fact written that the two continents were once conjoined. But somehow these declarations had escaped both serious scrutiny and general notice.
Wegener-unburdened by any prior geological expertise-launched into frenetic research. Among the facts he turned up were that the highlands of Scotland seemed to continue in the Appalachian Mountains of the United States, separated only by the Atlantic Ocean; the fossils of similar animals and plants had been found on both continents. He concluded with a sweeping observation: The lands as we knew them had been arranged by continental drift, a process by which all the continents had begun their existence fused into one gigantic expanse that he called Pangaea, or All Earth.
He convinced few contemporaries. Around the world, especially in the United States, hostile geologists denounced Wegener as a dilettante, a superficial interloper, and just dead wrong, according to Mott Greene, the author of a new biography of him. The coastal likenesses were a coincidence, they said. In 1930, the discredited Wegener died on Greenland in yet another attempt to find physical proof of the theory. It took four decades before a chance discovery revived his theories. …. To Mueller, considering all this in the early 1990s, now with his PhD and a position as a lecturer at the University of Sydney, what was missing was a reliable, mathematically grounded model that would make sense of the entire geological show from start to finish.
As a field, paleogeology had stayed on the boil. After Pangaea was accepted, scientists had excited a new stir by assembling geological evidence of prior supercontinents: first Kenorland, which would have broken up some 2.4 billion years ago, then Nuna, and after that, about 1 billion years ago, Rodinia. By this stage, multicellular organisms had appeared in the oceans, but the land would still have been bare of anything but bacteria and some algae. Rodinia begat Pangaea, which has hosted all of the complex plant and animal history with which we are familiar.
This was the defining tension underlying the half-century-long study of the supercontinents: That, unlike in other fields that deal in the very old, the scientists had no time machine. Astronomers, by looking through telescopes at galaxies billions of light years away, are transported back to the early universe. Paleontologists, by stumbling on ancient fossils, can look directly at remnants of prehistoric life. But no instrument or evidence had ever similarly teleported their paleogeologist comrades back to the age of supercontinents.
Instead, paleogeologists painstakingly pieced together their theories using disparate fragments of clues, mainly from the magnetic signatures in old rocks.
https://qz.com/577842/scientists-have-used-groundbreaking-technology-to-figure-out-how-the-earth-looked-a-billion-years-ago/
Richard Alley explains “The Biggest Control Knob: Carbon Dioxide in Earth’s Climate History”
https://dev-videos.com/videos/RffPSrRpq_g/Richard-Alley-The-Biggest-Control-Knob-Carbon-Dioxide-in-Earths-Climate-History
Richard Blane Alley (born 1957) is an American geologist and Evan Pugh Professor of Geosciences at Pennsylvania State University.[5] He has authored more than 240 refereed scientific publications about the relationships between Earth’s cryosphere and global climate change,[4] and is recognized by the Institute for Scientific Information as a “highly cited researcher.
So the history: 4.6 billions years ago, the sun’s output was lower (approx 70% of today’s levels), often referred to as the faint young sun. But we know there was liquid water on earth back then, and the only thing that could explain that is a stronger greenhouse effect. Nothing else works???-???orbital differences, for example, weren’t big enough. The best explanation for the process so far is the Rock-Weathering Thermostat. CO2 builds up in the atmosphere over time from volcanic activity. As this CO2 warms the planet through the greenhouse effect, the warmer climate increases the chemical weathering of rock, which in turn removes carbon dioxide through the formation of calcium carbonate, that gets washed into the sea and eventually laid down as sediment. Turn up the temperature, and the sequestration of CO2 in the rocks goes faster. If the earth cools down this process slows, allowing CO2 to build up again in the atmosphere. This is process is probably what has kept the planet in the right range for liquid water and life for most of the last 4 billion years.
But can we demonstrate it? The rock thermostat takes millions of years to work, because the principle mechanism is geological. One consequence is that the only way to get to a “snowball earth” (times in the Cryogenian period when the earth was covered in ice even down to the tropics) is that some other cause of change has to happen fast???-???faster than the rock-themostat effect.
An obvious piece of evidence is in the rock layers. Glacial layers are always covered from above by carbonate rocks, showing that increased carbonation (as the earth warmed) follows periods of icing. This shows part of the mechanism. But to explore the process properly, we need good CO2 paleo-barometers. The gold standard is ice core record. So far the oldest ice core record is 800,000 years, although we only have one record this old. Several records go back 450,000 years, and there are many more shorter records. The younger samples all overlap, giving some confidence that they are correct. We also now know a lot about how to sort out ‘good’ ice core record from poor (contaminated) ones.
But to back the evidence from the ice cores, there are other techniques with independent assumptions (but none as easy to analyze as ice cores). When they all agree, this gives us more confidence in the reconstructions. One example: growth of different plant species???-???higher CO2 gives preference to certain species. Similarly, different ways in which carbonate shells in the ocean grow, depending on pH of the ocean (which in turn is driven by atmospheric concentrations of CO2). Also the fossil-leaf stomata record. Stomata are the pores in leaves that allow them to breathe. Plants grow leaves with more pores when there is low CO2, to allow them to breathe better, and less when there is more CO2, to minimize moisture loss.
So, we have a whole bunch of different paths, none of which are perfect, but together work pretty well. Now what about those other controllers, beyond the rock-thermostat effect? CO2 is raised by:
He showed the graph reconstructing what we know of CO2 levels over the last 400 million years. Ice coverage is shown on the chart as blue bars, showing how far down towards the equator the ice reaches, and this correlates with low CO2 levels from all the different sources of evidence. 251 million years ago, pretty much every animal dies???-???95% of marine species wiped out, in the end-permian extinction. Probable cause: rapid widespread growth of marine green sulfur bacteria that use H2S for photosynthesis. The hydrogen sulphide produced as a result kills most other life off. And it coincides with a very warm period. The process was probably kicked off by greater vulcanism (the siberian traps) spewing CO2 into the atmosphere. When the ocean is very warm, it’s easy to starve it of oxygen; when it’s cold it’s well oxygenated. This starvation of oxygen killed off most ocean life.
Fast forward to the mid-cretaceous “saurian sauna”, when there was no ice at sea level at poles. Again, CO2 is really high again. High CO2 explains the warmth (although in this case, the models tend to make it a little too warm at these CO2 levels). Then there was one more blip before the ice ages. (Aside: CO2 is responsible for lots of things, but at least it didn’t kill the dinosaurs, a meteorite did). The paleocene-eocene thermal maximum meant big temperature changes. It was already hot, and the world gets even hotter. Most sea-floor life dies out. Acidic ocean. This time, the models have difficulty simulating this much warming. And it happened very fast, although the recovery process matches our carbon cycle models very well. And it shows up everywhere: e.g. leaf damage in fossil leaves at PETM.
But for many years there was still a mystery: The temperature and CO2 levels are highly correlated throughout the earth’s history, and with no other way to explain the climate changes. But occasionally there were places where temperature changes did not match CO2 changes. Over last couple of decades, as we have refined our knowledge of the CO2 record, all these divergences have gone. The mismatches have mostly dissapeared.
Even just two years Alley would have said something was still wrong in miocene, but today it looks better. Two years ago we got new records that improve the match. Two weeks ago, Tripati et. al. published a new dataset that agrees even better. So, two years ago, miocene anomalies looked important, now not so clear, it looks like CO2 and temperature do track.
But what do we say to people who say the lag proves current warming isn’t caused by CO2? We know that orbital changes (the Milankovitch cycles) kick off the ice ages???-???this was predicted 50 years before we had data (in the 1970s) to back it up. But temperature never goes far without the CO2, and vice versa, but sometimes one lags the other by about 2 centuries. And a big problem with the Milankovich cycles is that they only explain a small part of the temperature changes. The rest is when CO2 changes kick in. Alley offered the following analogy: credit card interest lags debt. By the denialist logic, because interest lags debt, then I never have to worry about interest and the credit card company can never get me. However, a simple numerical model demonstrates that interest is the bigger cause of debt (even though it lags!!). So, it’s basic physics. The orbits initially kick off the warming, but the release of CO2 then kicks in and drives it.
So, CO2 explains almost all the historical temperature change. What’s left? Solar irradiance changes, volcanic changes. When these things change, we do see the change in the temperature record. For solar changes, there clearly aren’t many, and they act like a fine tuning knob, rather than a major control. 40,000 years ago the magnetic field almost stopped (it weakened to about 10% of its current level), letting in huge amounts of cosmic rays, but the climate ignored it. Hence, we know cosmic rays are at best a fine tuning knob. Volcanic activity is important, but essentially random (“if volcanoes could get organised, they could rule the world”???-???luckily they aren’t organised). Occasionally several volcanoes erupting together makes a bigger change, but again a rare event. Space dust hasn’t changed much over time and there isn’t much of it (Alley’s deadpan delivery of this line raised a chuckle from the audience).
So, what about climate sensitivity (i.e. the amount of temperature change for each doubling of CO2)? Sensitivity from models matches the record well (approx 3°C per doubling of CO2). Recently, Royer et al conducted an interesting experiment, calculating equilibrium climate sensitivity from models, and then comparing with the proxy records, to demonstrate that climate sensitivity has been consistent over the last 420 million years. Hence paleoclimate says that the more extreme claims about sensitivity (especially those claiming very low levels) must be wrong.
In contrast, if CO2 doesn’t warm, then we have to explain why the physicists are stupid, and then we still have no other explanation for the observations. If there is a problem, it is that occasionally the world seems a little more sensitive to CO2 than the models say. There are lots of possible fine-tuning knobs that might explain these???-???and lots of current research looking into it.
https://thinkprogress.org/in-must-see-agu-video-richard-alley-explains-the-biggest-control-knob-carbon-dioxide-in-earths-a7cb5e4f3400/
How do we know the age of the Universe? If we can measure how the Universe is expanding today and how it has expanded throughout its entire history, we can know exactly what all the different components are that make it up. We learn this from a whole host of observations, including:
From direct measurements of the brightnesses and distances of objects in the Universe such as stars, galaxies and supernovae, allowing us to construct the cosmic distance ladder.
From measurements of large-scale-structure, the clustering of galaxies, and from baryon acoustic oscillations.
And from the fluctuations in the cosmic microwave background, a “snapshot” of the Universe when it was a mere 380,000 years old.
You put all of these things together, and you get a Universe that is made up, today, of 68% dark energy, 27% dark matter, 4.9% normal matter, about 0.1% neutrinos, about 0.01% radiation, and pretty much nothing else.
But you throw in how the Universe is expanding today, and we can extrapolate this back in time, and learn the entire expansion history of the Universe, and hence, its age.
The number we get???-???most precisely from Planck but augmented from the other sources like supernova measurements, the HST key project and the Sloan Digital Sky Survey???-???is that the Universe is 13.81 billion years old, with an uncertainty of just 120 million years. This means we’re confident in the age of the Universe to 99.1% accuracy, which is an amazing feat!
Yes , we have a number of different data sets that point to this conclusion, but in reality, it’s all the same method. We’re simply fortunate that there is a consistent picture that they all point towards, but in reality, any one of the constraints themselves is insufficient to say “this is exactly how the Universe is.” Instead, they all offer a variety of possibilities, and it’s only their intersection that tells us where we live.
If the Universe had the same current properties today but were made of 100% normal matter and no dark matter or dark energy, our Universe would be only 10 billion years old. If the Universe were 5% normal matter (with no dark matter or dark energy) and the Hubble constant were 50 km/s/Mpc instead of 70 km/s/Mpc, our Universe would be a whopping 16 billion years old. With the combinations of things we have today, however, we can confidently state 13.81 billion years is the age of the Universe, with a very small uncertainty. It’s an incredible feat of science.
And that’s legitimately one method. It’s the main one, it’s the best one, it’s the most complete one, and it’s got a ton of different pieces of evidence pointing towards it. But there is another, and it’s incredibly useful for checking our results.
It’s the fact that we know how stars live, burn through their fuel, and die. In particular, we know that all stars, when they’re alive and burning through their main fuel (fusing hydrogen into helium), have a specific brightness and color, and remain at that specific brightness and color only for a certain amount of time: until their cores start to run out of fuel.
At that point, the brighter, bluer and higher mass stars begin to “turn off” of the main sequence (the curved line on the color-magnitude diagram, below), evolving into giants and/or supergiants.
By looking at where that turn-off-point is for a cluster of stars that all formed at the same time, we can figure out???-???if we know how stars work???-???how old those stars in the cluster are. When we look at the oldest globular clusters out there, the ones lowest in heavy elements and whose turn-offs come for the lowest-mass stars out there, we find that they pretty consistently come in at an age of up to around 13.2 billion years, but not much older. (There are significant uncertainties of around a billion years on this, mind you.)
Ages of 12 billion years and up are very common, but ages of, say, 14 billion years and over are unheard of, although there was a period in the 1990s where ages of 14-16 billion years were often cited. (An improved understanding of stars and their evolution has bumped these numbers down.)
So all in all, we have two methods???-???one from our cosmic history and one from measuring local stars???-???that show us our Universe’s age is between 13 and 14 billion years old. It wouldn’t surprise anyone if we turned out to be as little as 13.6 or as much as 14.0 billion years old, but we’re not 13.0 or 15.0 billion years old with extreme certainty. Say we’re 13.8 billion years old with confidence, and now you know how we’ve figured it out!
How Old is the Universe?
Age may only be a number, but when it comes to the age of the universe, it’s a pretty important one. According to research, the universe is approximately 13.8 billion years old. How did scientists determine how many candles to put on the universe’s birthday cake? They can determine the age of the universe using two different methods: by studying the oldest objects within the universe and measuring how fast it is expanding.
The life cycle of a star is based on its mass. More massive stars burn faster than their lower-mass siblings. A star 10 times as massive as the sun will burn through its fuel supply in 20 million years, while a star with half the sun’s mass will last more than 20 billion years. The mass also affects the brightness, or luminosity, of a star; more massive stars are brighter.
Early stars aren’t the only way to place limits on the age of the universe. Dense collections of stars known as globular clusters have similar characteristics. The oldest known globular clusters have stars with ages that appear to be between 11 and 18 billion years old. The wide range comes from problems in pinpointing the distances to the clusters, which affects estimates of brightness and thus mass. If the cluster is farther away than scientists have measured, the stars would be brighter, thus more massive, thus younger than calculated.
“Just like archaeologists use fossils to reconstruct the history of the Earth, astronomers use globular clusters to reconstruct the history of the galaxy,” Andrea Kunder told Space.com. “There are only about 150 globular clusters known in the Milky Way Galaxy, so each of these globular clusters is an important tracer of the galactic halo and the formation of the Milky Way Galaxy.”
The uncertainty still creates a limit to the age of the universe; it must be at least 11 billion years old. It can be older, but not younger.
The universe we live in is not flat and unchanging, but constantly expanding. If the expansion rate is known, scientists can work backwards to determine the universe’s age, much like police officers can unravel the initial conditions that resulted in a traffic accident. Thus, finding the expansion rate of the universe - a number known as the Hubble constant - is key.
A number of factors determine the value of this constant. The first is the type of matter that dominates the universe. Scientists must determine the proportion of regular and dark matter to dark energy. Density also plays a role. A universe with a low density of matter is older than a matter-dominated one.
To determine the density and composition of the universe, scientists rely on missions such as NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) and The European Space Agency’s Planck spacecraft. By measuring the thermal radiation left over from the Big Bang, missions such as these are able to determine the density, composition and expansion rate of the universe. The leftover radiation is known as the cosmic microwave background, and both WMAP and Planck have mapped it. [INFOGRAPHIC: Cosmic Microwave Background: Big Bang Relic Explained]
In 2012, WMAP estimated the age of the universe to be 13.772 billion years, with an uncertainty of 59 million years. In 2013, Planck measured the age of the universe at 13.82 billion years. Both of these fall within the lower limit of 11 billion years independently derived from the globular clusters, and both have smaller uncertainties than that number.
https://www.space.com/24054-how-old-is-the-universe.html
The age of the Solar System (including the Earth), on the other hand, is measured by the radioactive decay of certain isotopes in rocks and meteorites. These isotopes (principally Potassium and Uranium) were created with the solar system. By measuring how much has decayed, we can very accurately determine how long it’s been since they (and the rest of the solar system) were formed. The oldest rocks on Earth have been destroyed by plate tectonics, so to get the age of the solar system, we turn to meteorites instead. The oldest such meteorites we have found suggest the age of their formation, and thus the age of the solar system, to be 4.568 Billion years.
http://curious.astro.cornell.edu/about-us/36-our-solar-system/the-earth/general-questions/19-how-do-we-know-the-age-of-the-universe-and-the-earth-intermediate
Evidence for evolution: anatomy, molecular biology, biogeography, fossils, & direct observation
https://www.khanacademy.org/science/biology/her/evolution-and-natural-selection/a/lines-of-evidence-for-evolution
Evolution - Scientific Theory
https://www.britannica.com/science/evolution-scientific-theory
Three Pieces of Evidence That Prove Evolution is a Fact
https://futurism.com/three-main-pieces-of-evidence-supporting-evolution/
Evidence for evolution - rapid changes
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/evolution/evolutionrev4.shtml
Major Themes in Evolution
https://www.nap.edu/read/5787/chapter/3
Do gaps in the fossil record present serious difficulties for the theory of evolution?
http://www.sciencemeetsreligion.org/evolution/fossils.php
Law of Fossil Succession
http://ib.bioninja.com.au/standard-level/topic-5-evolution-and-biodi/51-evidence-for-evolution/fossil-record.html
The Fossil Fallacy Creationists’ demand for fossils that represent “missing links” reveals a deep misunderstanding of science
https://www.scientificamerican.com/article/the-fossil-fallacy/
Simulating evolution: How close do computer models come to reality?
https://theconversation.com/simulating-evolution-how-close-do-computer-models-come-to-reality-57538
Evolution IS a Blind Watchmaker
In this video I deconstruct the broken watch straw man argument used by creationist / ID supporters to attack evolution.
https://www.youtube.com/watch?v=mcAq9bmCeR0
Evolution Simulator of Creatures Jumping Vertically
https://www.youtube.com/watch?v=DTUlgZ2qLg8
Harnessing evolutionary creativity: evolving soft-bodied animats in simulated physical environments
https://www.youtube.com/watch?v=CXTZHHQ7ZiQ
Evolving Swimming Soft-Bodied Creatures F. Corucci, N. Cheney, F. Giorgio-Serchi, J. Bongard, C. Laschi “Evolving soft locomotion in aquatic and terrestrial environments: effects of material properties and environmental transitions”
https://www.youtube.com/watch?v=4ZqdvYrZ3ro
Tiktaalik fossils reveal how fish evolved into four-legged land animals
https://www.theguardian.com/science/2014/jan/13/tiktaalik-fossil-fish-four-legged-land-animal
8 Scientific Discoveries That Prove Evolution is Real
https://io9.gizmodo.com/8-scientific-discoveries-that-prove-evolution-is-real-1729902558?IR=T
Four Famous Transitional Fossils That Support Evolution
https://www.forbes.com/sites/shaenamontanari/2015/11/17/four-famous-transitional-fossils-that-support-evolution/#500754d22d8d
Fossils Reveal Truth About Darwin’s Theory
https://www.livescience.com/3306-fossils-reveal-truth-darwin-theory.html
Transitional forms
https://evolution.berkeley.edu/evolibrary/article/lines_03
List of transitional fossils
https://en.wikipedia.org/wiki/List_of_transitional_fossils
Caihong juji: Jurassic Bird-Like Dinosaur Had Iridescent Feathers
http://www.sci-news.com/paleontology/caihong-juji-jurassic-bird-like-dinosaur-iridescent-feathers-05637.html
Remains of oldest known relative of modern birds discovered in China
https://www.theguardian.com/science/2015/may/05/remains-of-oldest-known-relative-of-modern-birds-discovered-in-china
New Zealand Evolutionary Evidence
http://sci.waikato.ac.nz/evolution/NZevidence.shtml
Genetic study finds evidence that we’re still evolving
https://newatlas.com/genetic-study-human-evolution/51221/
Animals are evolving faster than you think - here’s the living proof
https://theconversation.com/animals-are-evolving-faster-than-you-think-heres-the-living-proof-52087
Ten Species That Are Evolving Due to the Changing Climate
https://www.smithsonianmag.com/science-nature/ten-species-are-evolving-due-changing-climate-180953133/
Are animals still evolving?
https://science.howstuffworks.com/life/evolution/are-animals-still-evolving.htm
7 Animals That Are Evolving Right Before Our Eyes
http://www.cracked.com/article_19213_7-animals-that-are-evolving-right-before-our-eyes.html
10 Species That Are Evolving Right Now
https://listverse.com/2016/12/23/10-species-that-are-evolving-right-now/
Not-So-Intelligent Design: Evolution’s Worst Ideas
https://www.scientificamerican.com/article/recommended-not-so-intelligent-design-evolution-s-worst-ideas/
Evolution is The “Not-So-Intelligent Designer”
http://www.patheos.com/blogs/rationaldoubt/2017/02/evolution-not-intelligent-designer/