I’m pretty good about ice ages. This is the first I’ve heard of an ice age more recent than 3 million years… but not part of the 8 in a row.
What is your source for an ice age 2 million years ago?
Perhaps you are using a BIGGER definition of “ice age-ism”?
From the wiki article:
“The current ice age, the Pliocene-Quaternary glaciation, started about 2.58 million years ago during the late Pliocene, when the spread of ice sheets in the Northern Hemisphere began.”
“Since then, the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000- and 100,000-year time scales called glacial periods, glacials or glacial advances, and interglacial periods, interglacials or glacial retreats. The earth is currently in an interglacial, and the last glacial period ended about 10,000 years ago. All that remains of the continental ice sheets are the Greenland and Antarctic ice sheets and smaller glaciers such as on Baffin Island.”
It then goes on to specify the more punctuated sense of ice ages… calling them Ice “periods” (!!!) - starting 800,000 years ago.
The bigger definition seems to be based on the existence or advancement of ANY ice sheets! The wiki writer wants to reserve “Age” for when “glaciation periods” become possible!
P.S.: a look at a temperature graph shows various mini glacial periods at less than 100k intervals … with clear, Full-On! 100,000 year “icings” only in the last 800,000 years!
Hi @swamidass,
Thank you very much for your very thorough critical evaluation of the Biorxiv paper by Stoeckle and Thaler. I can see now that its conclusions are overblown, and its science is rather faulty. Now that it has been published, I hope you write a rebuttal.
So, what are your thoughts on the best way to define a species? Or is there something wrong with that question?
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If I may interject with my own thoughts regarding the question you ask @swamidass:
I think a YEC preacher or two has actually stumbled across a good definition:
I would call it the “Brought Forth Abundantly” definition of “Kinds”.
Rather than use “kind” to mean “categories” or “types”, which seems terribly subjective… the test seems to be whether animals can “bring forth abundantly” their kind!
Gen 1:20-21
And God said, Let the waters
bring forth abundantly
the moving creature that hath life, and fowl that may fly above the earth in the open firmament of heaven.
And God created great whales, and every living creature that moveth, which the waters
brought forth abundantly, after their kind,
This is virtually identical with Mayr’s reproductive definition of Species, which he fashioned back in 1942!
“Although Charles Darwin and others posited that multiple species could evolve from a single common ancestor, the mechanism by which this occurred was not understood, creating the species problem. Ernst Mayr approached the problem with a new definition for species. In his book Systematics and the Origin of Species (1942) he wrote that a species is not just a group of morphologically similar individuals, but a group that can breed only among themselves, excluding all others.”
If this definition is strictly employed, there are some interesting suprises. Frankly, it seems like the idea definition of “species” and of “kinds” as per the Good Book!
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From @sygarte:
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I see that Answers in Genesis has mocked this study:
Ham’s article at the AIG website shows an appalling misunderstanding of the topic. He also carefully quote-mines the paper. His article is quite sad.
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General policy is to post link to article always, when referenced this way. Please do.
The link paste failed in my previous post so here is the complete post as it should have been:
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I was very happy to come across your analysis. The TechTimes article was posted on a large science teacher FB group I am a member of and I was frustrated by the lack of skepticism for both the article, the quotes, the findings, etc.
I couldn’t believe that it had been published and did some digging (and came upon your forum). Correct me if I am mistaken but it seems that it was not published in Journal of Human Evolution, but through a small journal out of Florence, Italy titled Human Evolution.
Human Evolution: Why should mitochondria define species? Stoeckle M.Y., Thaler D.S.
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Ah, that explains my confusion. Thanks for the clarification. One of the popular science articles referred to it at the Journal of Human Evolution but I’ve refreshed the current articles from this journal many times and wondered where it was. Its starting to make more sense now. I was surprised that the article on the Bio pre-print service was identical but now it looks like this very small journal simply picked up an article that other journal did not deem worthy. Sadly, to those like young-earth creationists that are looking for quotes that fit their paradigm, they won’t be discerning about the source or the critiques and their audience will not realized that some sources are more credible than others.
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Joel, that explains a lot for me to. I was forced to read the entire painful 30 pages of the paper, since people all over social media were talking about the popular articles, and I knew something was wrong. I was pretty horrified at what I read. As Joshua has pointed out, there are some major technical and conceptual errors in the analysis (which went a bit over my head), but I simply couldnt make sense of the writing. I am quite familiar with the fairly recent problem of small, low IF journals publishing stuff, and also confused J Human Evolution with this one.
I hope enough people write explanations to help defuse this false turmoil.
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Nice to meet you @CSapnas, and welcome to the forum. Please post a link to my response to that FB group. It would be very depressing if that article actually made it into classrooms.
And thanks for getting to the bottom of that too. I am still surprised that got past peer review. A genuinely bad paper that we, who engage the public, will be recovering from for a while.
@Joel_Duff, have fun responding to the AIG article on this.
This article were correct, it would falsify their hyper-evolution model of kinds rapidly diversifying after the flood. An honest article would make that clear. I’m just speechless in response to the three point justification given from Nathaniel Jeanson.
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So much wrong with Ham and Jeanson’s article it’s hard to know where to begin and I don’t have time right now to work through it all. I thought the same thing about Jeanson when I read the original research article. And yet, Jeanson/Ham tries hard to make it sound like this all supports rapid diversification. And yet they seem to conflate “kind” with species in the space of two paragraphs. They seem to suggest that we would expect discrete differences between “kinds” and yet the Human Evolution paper was attempting to make the point that species are discrete units. How could each species have the same amount of mtDNA variation as humans if 100 species came from a single mtDNA lineage on the ark? Such a mess but so difficult to communicate to the public when they can just quote one line about “species being about the same age.”
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I just shared and was pleasantly surprised & relieved that another member posted her husband’s (he is also an established scientist like yourself) takedown as well and he had linked to your post here already.
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Thanks for the update. I hope it is a good teaching point in class, rather than a yet another place journalists get it wrong and confuse everyone. =)
Can you link to the other critique?
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Would you care to comment on the below comment on the original article from quora.
Thank you,
Jan
link:
http://qr.ae/TUpFGP
Patrick Foley, PhD in evolutionary genetics UCDavis:
The article linked in the question is sensational and does not fully reflect the original scientific paper which is far more sophisticated. To see it go to Why Should Mitochondria Define Species? It is a good article, and has me thinking, but I wish we had something similar for nuclear DNA. Also note: one of the authors David Thaler, is a quorum writer David Thaler).
Some points to consider in interpreting the article and the paper:
This “sweeping gene survey” was done on a single locus found in mitochondrial DNA. And it is not a random locus; COI gene was chosen for DNA barcoding because it was simultaneously rather conserved, and yet showed some variation between species. There is good reason to think that this gene is not typical of the whole genome. Useful, but not typical. Mitochondrial DNA has very different transmission dynamics than nuclear DNA. Most of our DNA is nuclear. Most of our DNA is not tidily useful as a barcode.
The first Homo sapiens fossils go back at least to 300,000 years ago at Jebel Irhoud Morocco … if you are a splitter (Jebel Irhoud - Wikipedia). If you are a lumper and lump Neanderthal in as a subspecies of Homo sapiens, then this species goes back perhaps 500,000 years (400,000–800,000 is our common ancestor). We certainly did not appear in the last 200,000 years as the article states. The last common ancestor of our mitochondrion did however occur about 150,000 years ago (Mitochondrial Eve - Wikipedia). This is perhaps a common pattern: mitochondrial eves are often more recent than the speciation “event”.
The Pleistocene (2.5 MYA to essentially today) is an unusual time in faunal history. There have been 100,000 year cycles in climate over much of the globe, even the tropics. This has led to higher speciation and extinction rates in the fossil record (and also stronger selection for migratory tendencies, opportunistic, disturbance loving species etc.). GG Simpson estimated from the rich mammalian fossil record of the Cenozoic (about 65 MYA ago to today) that a typical mammal species persists on average 1 MY in the record. Not so in the Pleistocene. Species turnover reflects the rapid climatic changes.
On the whole, I do not think the most interesting take-home lesson of the paper is that present species are relatively young. I think many are, partly because of rapid Pleistocene turnover. But much of the apparent youth of the COI gene is due to the peculiarities of mitochondrial population genetics.More interesting to me is the idea that there is a distinct genetic gap between sister species. I suspect some of this is due to the particular, very peculiar status of the COI gene. I do not think it is due to punctuated equilibrium. Punctuated equilibrium would provide one of the two sister species with an impoverished subset of the other sister. This is not (as far as I can tell from the original paper) the observed phenomenon. Perhaps David could speak to this.
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To be precise, 2.5 MYA is when the Earth started to turn colder, with permanent ice appearing in Antarctica (and maybe at the north pole as well).
The actual 100,000 year cycles didn’t kick in until 800,000 YA, driven by the Milankovitch Cycles, which is a combinatino of 3 different overlapping cycles, with the longest cycle (100k) eventually taking the dominant position). In 800,000 years there have been 8 major glaciations.
My pet theory for why the cycles didn’t actually cleanly start 2.5 MYA (or at any other time closer to 2.5 MYA than to 800,000 years ago), is that there was still too much CO2 in the atmosphere. As the planet cooled, more of the atmospheric CO2 dissolved back into the oceans and began to be “fixed” in frozen sediments in the seas.
The Earth then, amazingly, entered a climate sweet spot, where alternating between 180 ppm and 280 ppm was enough alternately put 1 mile glaciers over the future New York CIty … followed by a reversal in the cycle where oceans would rise and virtually all glaciers (would melt).
@Jan welcome to the forums.
He is a legitimate scientist, who does good work. Any harshness you may detect is directed at the original paper, not at this review by Dr. Foley.
Exactly correction.
True too. It is very hard to calibrate the Mitochondria clock for this reason, and most of the dates calculated were not calibrated.
Exactly. They mitochondrial coalescence will take place in 1/4 the time (on average) than nuclear DNA, which usually places it far more recent than speciation. Coalescence is not a marker for speciation, but something entirely different. The original authors had it wrong.
That is exactly right too. The Fossil record is a better way to look at speciation and extinction rates.
Exactly right. Mitochondrial coalescence does not correspond (nor do we expect it to correspond) with bottlenecks or speciation.
Once again, this is just a single locus coalescent. If we were to look at more DNA (e.g. in the autosome) we would immediately see a different story.
5 posts were merged into an existing topic: Did 90% of Animal Species Appear about the Same Time as Human Beings?