(Oct. 12, 2017).
Tianyuan Cave (photo) is near modern Beijing. In 2007 researchers found human remains radio carbon dated to between 42,000 and 39,000 years ago. That is well after the first groups of Aboriginal people arrived in Australia. Now the results of new DNA analysis have been published in Current Biology. The formal summary of results follows. Further comments follow the summary.
By at least 45,000 years before present, anatomically modern humans had spread across Eurasia, but it is not well known how diverse these early populations were and whether they contributed substantially to later people or represent early modern human expansions into Eurasia that left no surviving descendants today. Analyses of genome-wide data from several ancient individuals from Western Eurasia and Siberia have shown that some of these individuals have relationships to present-day Europeans while others did not contribute to present-day Eurasian populations. As contributions from Upper Paleolithic populations in Eastern Eurasia to present-day humans and their relationship to other early Eurasians is not clear, we generated genome-wide data from a 40,000-year-old individual from Tianyuan Cave, China, to study his relationship to ancient and present-day humans. We find that he is more related to present-day and ancient Asians than he is to Europeans, but he shares more alleles with a 35,000-year-old European individual than he shares with other ancient Europeans, indicating that the separation between early Europeans and early Asians was not a single population split. We also find that the Tianyuan individual shares more alleles with some Native American groups in South America than with Native Americans elsewhere, providing further support for population substructure in Asia and suggesting that this persisted from 40,000 years ago until the colonization of the Americas. Our study of the Tianyuan individual highlights the complex migration and subdivision of early human populations in Eurasia.
Melinda A. Yang, Xing Gao, Christoph Theunert, Haowen Tong, Ayinuer Aximu-Petri, Birgit Nickel, Montgomery Slatkin, Matthias Meyer, Svante Pääbo, Janet Kelso, Qiaomei Fu, 40,000-Year-Old Individual from Asia Provides Insight into Early Population Structure in Eurasia, Current Biology, Volume 27, Issue 20, p3202–3208.e9, 23 October 2017Recognising my knowledge limitations, I drew the following main points from the latest results. My indebtedness to Anne will be clear if you look at her article. :
- The date ranges mean that Tianyaun Man. is probably at least 20,000 years younger than the first Aboriginal occupation of Sahul, the name given to the bigger Australian continent when sea levels were lower.
- The DNA results show elements of Neanderthal genes but no trace of the Denisovan genes to be found in Aboriginal DNA. On the basis (as seems to be the case) that the Denisovans were reasonably widely spread across Eurasia, this suggests to my mind that Tianyaun Man came from a later migration wave,
- Tianyuan Man shares DNA with one ancient European—a 35,000-year-old modern human from Goyet Caves in Belgium. But he doesn’t share it with other ancient humans who lived at roughly the same time in Romania and Siberia—or with living Europeans.
- Tianyuan Man is most closely related to living people in east Asia—including in China, Japan, and the Koreas—and in Southeast Asia, including Papua New Guinea and Australia.This suggests that the Tianyuan Man was not a direct ancestor, but rather a distant cousin, of a founding population in Asia that gave rise to present-day Asians.
- Tianyuan Man was a distant relative of Native Americans living today in the Amazon of South America, such as the Karitiana and Surui peoples of Brazil and the Chane people of northern Argentina and southern Bolivia. But he is not an ancestor to ancient or living Native Americans in North America, which suggests there were two different source populations in Asia for Native Americans.
Current Anthropology has an interesting article by Professor Robin Dennell, "Human Colonization of Asia
in the Late Pleistocene: The History of an Invasive Species" (Current Anthropology Volume 58, Supplement 17, December 2017) The summary reads:
Narratives of “Out of Africa 2”—the expansion of Homo sapiens across Asia—emphasize the pattern of human dispersal but not the underlying processes. In recent years, the main debates have been over the timing and frequency of dispersal. Here, I treat these issues as subordinate to biogeographic ones that affected the behavior of humans in Asia as an invasive species that colonized new environments and had negative impacts on indigenous hominins. I suggest that attention should focus on three issues: (i) geographic factors that molded human dispersal across Asia, (ii) behavioral changes that enabled humans to overcome previously insurmountable barriers, and (iii) demographic considerations of human dispersal and colonization of Asia, including interactions with indigenous competitors. Although a strong case can be made that humans dispersed across southern Asia before 60 ka, this should not detract from attention on the underlying processes of dispersal and colonization.
I found the article provided a useful summary framework. The geographic analysis in particular filled a gap in my knowledge The MIS in the paper, by the way, stands for Marine isotope stage. I wasn't really familiar with the term so looked it up. According to Wikipedia:
Marine isotope stages (MIS), marine oxygen-isotope stages, or oxygen isotope stages (OIS), are alternating warm and cool periods in the Earth's paleoclimate, deduced from oxygen isotope data reflecting changes in temperature derived from data from deep sea core samples. Working backwards from the present, which is MIS 1 in the scale, stages with even numbers have high levels of oxygen-18 and represent cold glacial periods, while the odd-numbered stages are troughs in the oxygen-18 figures, representing warm interglacial intervals.