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6 Oct, 5 tweets, 1 min read
Most people have around a chromosome's worth of DNA from Neandertals, spread in small pieces across all 46 chromosomes.
Or, if you're of male sex, 45 out of 46 of them.
For western Eurasian peoples, the average amount of Neandertal DNA across the genome is around 120 megabases. Eastern Eurasian peoples have a bit more. Chromosome 13 is 114 Mb and 12 is 133 Mb.
African and African diaspora peoples have between 30 and 70 megabases of Neandertal DNA, with a lot of variation. Chromosome 21 has 46 Mb, chromosome 20 has 64 Mb.
One of the striking things about Neandertal DNA in living people is that Neandertal segments are more often in parts of chromosomes with fewer genes. Chromosomes also vary enormously in gene number. Chr 12 has more than 1000 genes. Chr 13 has a little over 300.

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More from @johnhawks

John Hawks Profile picture
3 Oct
I'll be making a tabulation of Neandertal specimens that have yielded molecular (DNA, proteomic) sequence information. I know there are more than 30 but I'd like to get an actual count and link photos where possible. This will take a while, and I'll add to this thread as I go.
The first mtDNA fragments published from any Neandertal specimen were from the humerus of the Neandertal 1 skeleton, from the Kleine Feldhofer Grotte near Mettmann, Germany. The partial skeleton was recovered in 1856. Sequencing by Matthias Krings et al. doi.org/10.1016/S0092-… Figure from Krings et al. 1...
Ralf Schmitz and Jürgen Thissen relocated sediments from the Kleine Feldhofer Grotte, excavating in 1997 and 2000. They found new bone fragments that refit the Neandertal 1 skeleton and a humerus fragment (NN 1) that must represent a second individual. doi.org/10.1073/pnas.1…
Read 11 tweets
John Hawks Profile picture
27 Sep
Sometime between 370-150,000 years ago Neandertals got a Y chromosome from a more modern-like source population. This ultimately spread throughout all later Neandertal populations from which anyone has sampled DNA. Map of Europe and western Asia, showing range of Neandertal
The Neandertals and Denisovans originated from a common source population with African ancestors of modern humans sometime between 600 and 700,000 years ago. Population model of Neandertal Y chromosome introgression fr
This means that Neandertals and their Y chromosome donor population had begun to differentiate from each other between 230,000 and 600,000 years before this Y chromosome introgression happened. Neanderthal artist rendering at the Neanderthal Museum, Germ
Read 8 tweets
John Hawks Profile picture
24 Sep
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...
Read 8 tweets
John Hawks Profile picture
19 Sep
Generally, human chromosomes are numbered in order of length. Chromosome 1 is the longest, then 2, and so on. Most people know the sex chromosomes are exceptions; X is longer than 8, Y shorter than 20. Fewer know that chromosome 20 is longer than 19. And 22 is longer than 21. Human karyotype illustratio...
In the 1950s and 1960s, there was a lot of diversity in how different research groups numbered human chromosomes. Length was an obvious criterion, but to reliably sort karyotypes, scientists had to rely on additional characteristics including centromere position and arm lengths. Chromosome numbers from Lej...
The human genetics community worked to standardize the nomenclature of chromosomes in the 1960s, settling on today's numbers, before methods of measuring chromosome length were precise enough to accurately rank relative lengths of the shortest chromosomes.
Read 5 tweets
John Hawks Profile picture
27 Aug
Online/virtual professional conferences have been falling into my inbox with suddenly "significantly reduced registration fees" and "extended deadlines to take advantage of new prices". You can smell the desperation. There are better ways.
If you're going to treat a remote/online conference so explicitly as a product, then you need to show (not tell) your customers what value you are providing *beyond* the normal in-person event, because you're *removing* many of the benefits of in-person.
Why are you sending e-mails about an event months away without something *already online* that potential attendees can sample? If this is going to work, it's not because everyone agrees to log on to a registration-screened WebEx session 3 months from now.
Read 6 tweets
John Hawks Profile picture
13 Aug
New research by Lyn Wadley and her team from Border Cave demonstrates use of grass bedding by hominins 200 ka. Cool finding, and I think this is just scratching the surface of what is out there but historically unobserved. science.sciencemag.org/content/369/65… Images of microscopic plant...
Living great apes make nests, a behavior they learn at very early ages. This suggests nest-construction goes back to at least the human-orangutan divergence ca. 12 Ma. I would bet Australopithecus used some form of bedding or nests. doi.org/10.1073/pnas.1…
What remains is for us to investigate the right sites with methods that can detect the evidence. Grass transport is a good marker, and bedding use already demonstrated for Neanderthals at several sites. doi.org/10.1016/j.jas.… doi.org/10.1006/jasc.2…
Read 4 tweets

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