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John Hawks Profile picture
@johnhawks
Sep 24, 2020 • 8 tweets • 3 min read • Read on X
Love to see this new work from @fleventy5 @jfkelso @maxplanckpress outlining Neandertal and Denisovan Y chromosomes. New evidence of genetic mixture of Neandertals and third population closer to today's people. @ScienceMagazine
science.sciencemag.org/content/369/65… Population model for Neande...
I strongly hesitate to use the term "modern humans" in this context. The Y chromosome of Neandertals is from a Y clade that is extinct today, outside the range of present-day Y variation. What we don't know is where that Y clade fit into our structured ancestral populations.
Both the Y chromosome (~250ka) and mtDNA (~200ka) of modern humans have MRCA younger than the time we think that today's populations of modern people began to differentiate (~300ka). Of course, any of these dates could be wrong...
...but a likely hypothesis is introgressive replacement of Y and mtDNA in some early modern populations from others. The reason for such adaptive introgression in these populations would be the same as Neandertals: small population size, high drift, deleterious fixed mutations.
The story is not (or not only) that Neandertals picked up these gene systems from "moderns", but that most early moderns also picked them up. The term "moderns" to most people connotes one panmictic gene pool. But we now know that our ancestors were anything but that.
People on various channels are asking me, if Neandertals got their mtDNA and their Y chromosome from "modern" humans, how can we consider them a distinct species? After all, both their maternal and paternal lines came from us! This is a good question to be asking.
If you're wondering, it's worth a look at the ancient DNA papers that are generating these results. Very few of them use the term "Homo neanderthalensis" at all. As a concept, it has not been useful for explaining the genetic patterns.
One last thing about the new paper: It's very interesting in light of all the mtDNA and Y introgression that Denisovan Y chromosome divergence is right on the expected 700ka time range.

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More from @johnhawks

John Hawks Profile picture
May 17, 2023
Quite like the new paper by my @UWMadison colleague @apragsdale. Fun to see lots of people newly discovering these ideas about metapopulation models! A couple of notes:
nature.com/articles/s4158…
An implication of this population model is that the structure of our species, Homo sapiens, began to emerge several hundred thousand years earlier than the dispersal that led to Neandertal and Denisovan populations.
When added to other evidence of recurring gene flow between Neandertal and African ancestral populations, this very strongly implies that Neandertals are Homo sapiens.
Read 5 tweets
John Hawks Profile picture
Mar 18, 2022
So this seems very unpopular for some reason, but humans DID evolve from apes. We did not evolve from chimpanzees, gorillas, or any other living apes. They are our cousins. Our close fossil relatives were like living great apes in many ways and more like humans in others. MRD skull of Australopithecus anamensis on the right with a
Today's great apes, including chimpanzees and bonobos, two species of gorillas, and three species of orangutans, are a small surviving remnant of the diversity of apes that once existed. Each evolved in ways that helped them survive, just as our ancestors did. Tree showing the diversity of living great apes and humans.
Paleontologists have discovered many more forms of extinct apes than living ones. They were adapted to their time and place, some Asian, some African, and some European, but did not survive to the present day. Many of them lived in the period before 5 million years ago. Chart showing today's apes on a tree with time of existence
Read 7 tweets
John Hawks Profile picture
Dec 8, 2021
Some discussion in comments last week in @ScienceMagazine about "paleodemes" with a short defense of the value of the concept. I think the paleodeme concept has most of the problems of paleo species concepts with none of their benefits. science.org/doi/10.1126/sc…
The person probably most responsible for the paleodeme concept in human origins is Clark Howell, whose 1999 paper "Paleo-Demes, Species Clades, and Extinctions in the Pleistocene Hominin Record" defined (although it did not first introduce) the concept. journals.uchicago.edu/doi/abs/10.108…
As presented by Howell, a paleodeme corresponds to a regional sample of fossils across a delimited range of time, with some morphological distinctiveness. These were groups like "Neandertal", "Skhūl/Qafzeh", or "Petralona/Atapuerca-Sima".
Read 5 tweets
John Hawks Profile picture
Aug 13, 2021
Interesting paper on cutmark evidence from Olduvai, further substantiating early access to animal carcasses by tool-wielding Early Pleistocene hominins. @SciReports nature.com/articles/s4159… Cutmark evidence on animal bones from Olduvai Gorge, from Do
The paper's discussion raises lots of reasons why the anatomy of early Homo supports the idea that they were competent hunters. On this I don't disagree, but I think that focusing on "early Homo" here is misleading for several reasons.
First, "early Homo" fossils overlap substantially in anatomy with Australopithecus and Paranthropus. So much that we cannot always tell them apart (including long-standing arguments about well-known and not-so-fragmentary fossils).
Read 9 tweets
John Hawks Profile picture
Jun 25, 2021
So, Homo longi. It's such a good name. Dragon people. And an amazing skull discovery. Adds to our knowledge of the Middle Pleistocene in China. But it's sad that the name is not going to stay. cell.com/the-innovation… Harbin skull viewed from the front. Photo by Wei Gao, from T
The boring reason why we can't use the Homo longi name is technical. The research puts the Harbin skull together with the Dali skull, and Xinzhi Wu gave that the name Homo sapiens daliensis more than 40 years ago. So IF there's a species, it has to be H. daliensis. Phylogenetic morphology analysis of Harbin skull, showing it
In case you wonder how close Harbin looks to Dali, here is Harbin on the left and Dali (which has some crushing to the maxilla) on the right. As Weidenreich might have said, they resemble each other as closely as one egg resembles another. Harbin skull (left) compared with Dali skull (right)
Read 13 tweets
John Hawks Profile picture
Jun 24, 2021
The new report of fossil material from Nesher Ramla, Israel, claims a "previously unknown archaic Homo population" some 140,000 years ago. It's a big claim in an area where most scientists have thought that early modern humans and Neandertals interacted. science.sciencemag.org/content/372/65… Mandible from Nesher Ramla. From Hershkovitz et al. 2021 htt
Looking at the morphology of the mandible NR-2, it falls within the variation of fossils attributed to Neandertals, and is similar to Krapina, which is around the same age, and Sima, which are early Neandertals. This seems like a basic early Neandertal jaw. PC plot showing position of Nesher Ramla 2 next to Neanderta
The other fossil NR-1 is a complete right parietal bone and fragments of the left parietal. The analysis of shape places is near late Neandertals and early Neandertals, but a bit less "barrel-shaped", thereby similar to generalized H. erectus and African Middle Pleistocene Homo. PC plot of Nesher Ramla 1 parietal bone showing its position
Read 11 tweets

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