In this engaging discussion, paleoanthropologist John Hawks sheds light on our complex ancestry. He revisits the past, exploring the significant contributions of Neanderthals and Denisovans to modern humans. Hawks reveals how the ancient DNA revolution has reshaped our understanding of human evolution. He highlights the unique evolutionary paths of various hominins and the challenges in interpreting fossil records. With insights into genetic diversity and archaic admixture, this conversation demystifies the intricate web of human ancestry.
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Introgression Explains Patches Of Ancient Diversity
Early genome data showed a recent major shift in allele frequencies plus pockets of deeper diversity that didn't fit a pure Out-of-Africa model.
John Hawks proposed introgression from archaic groups to explain those ancient patches in modern genomes.
insights INSIGHT
Archaic Admixture Was Global, Not Local
Ancient DNA revealed small but widespread Neanderthal ancestry outside Africa and a distinct Denisovan contribution concentrated in Oceania.
Hawks emphasizes that archaic admixture was global and unexpected in its geographic distribution.
insights INSIGHT
Tiny Bands, Big Genetic Echoes
Pleistocene populations were small, fragile hunter-gatherer bands, so many contacts left little archaeological trace yet produced genetic admixture.
Hawks compares these brief contacts to Viking settlement traces to show why admixture signatures persist despite sparse archaeological records.
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Today on Unsupervised Learning, Razib talks to John Hawks, a paleoanthropologist who has been a researcher and commentator in human evolutionary biology and paleoanthropology for over two decades. With a widely read weblog (now on Substack), a book on Homo naledi, and highly cited scientific papers, Hawks is an essential voice in understanding the origins of our species. He graduated from Kansas State University in 1994 with degrees in French, English, and Anthropology, and received both his M.A. and Ph.D. in Anthropology from the University of Michigan, where he studied under Milford Wolpoff. He is currently working on a textbook on the origins of modern humans in their evolutionary context. Hawks has already been a guest on Unsupervised Learningthreetimes.
In this episode, Razib and Hawks focus on a very specific question: What were the different contributions to the heritage of modern humans in a world more than 200,000 years ago that was inhabited by at least half a dozen hominin species? First, Hawks takes us back to the year 2000 and his early work extending a more multiregional framework of human evolution, exploring what could be gleaned from the archaeological and paleontological record. Then Razib and Hawks discuss the ancient DNA revolution and the discovery that modern humans had ancestry from Neanderthals, as well as from an entirely new species, the Denisovans. They also examine the fact that, unlike Neanderthals, Denisovans appear to have been separated into very different regional populations that made distinct contributions to various modern populations. Razib also asks Hawks about the discovery of new pygmy human species in Luzon, as well as the current state of research on Homo naledi in South Africa and the Hobbits of Flores. Hawks contends that DNA will likely be extracted from all these lineages at some point and, if not, protein sequence data may be obtained. This would finally give researchers the statistical power to evaluate the possibility of extremely archaic admixture events. Hawks and Razib also address the potential role of natural selection driven by introgressed genes from sister lineages of humans and how this shaped modern variation.
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