Denisovans, Homo longi and the Chinese Fossils that Reshape Human Evolution

The video reviews how the discovery of Denisovans in 2010, together with controversial fossils from China, is reshaping our understanding of human evolution. It covers the identification of a third lineage alongside Homo sapiens and Neanderthals, the Harbin fossil, the Yunshan/ Yukhan material, and the evolving view on how interbreeding with Denisovans and Neanderthals contributed to the modern human genome. The conversation also discusses taxonomic naming debates, deep divergence times, and the geographic scope of Denisovan distribution from Siberia to the Tibetan plateau and beyond, as well as questions about the common ancestor of all these groups.

Introduction and Breakthroughs

New Scientist interviews Chris Stringer about the rapid evolution of our understanding of ancient humans, focusing on Denisovans and the recent debates over Homo longi. The conversation highlights the 2010 genetic discoveries that revealed Denisovans as a distinct lineage alongside Neanderthals and modern humans, and how complete Neanderthal genomes opened new avenues for studying interbreeding and genetic exchange.

Key Fossils and Genomes

The Harbin cranium, a nearly complete 146,000 year old fossil, demonstrates a blend of features that tie it to Denisovans while exhibiting a Homo sapiens like facial morphology. Proteomic data and DNA evidence support this assignment. Other Chinese specimens such as Dali, Jinhushan, and Hualongdong are increasingly thought to belong to the Denisovan group, expanding the geographic scope of this lineage beyond Denisova Cave in Siberia to the Tibetan plateau and coastal China.

The Yunshan/Yukhan Debate and Homo longi

Reconstructed Yunshan fossils present a brain size and facial structure that defy straightforward classification. Although methods initially align with Homo erectus for a million-year-old brain, the skull shows features more consistent with a Denisovan-like lineage. Stringer and colleagues argue this supports a longi group origin, suggesting a deep Denisovan emergence dating back about a million years and prompting calls to potentially rename the Denisovans as Homo longi, though this remains controversial.

Interbreeding and the Human Family Tree

The interview explains how Neanderthals and Denisovans contributed DNA to modern humans as Homo sapiens expanded out of Africa around 60,000 years ago. Neanderthal DNA persists in most non-African populations, while Denisovan DNA is strongest in some populations in Oceania and Southeast Asia, with multiple interbreeding events across different Denisovan groups. This complex history challenges simple trees and emphasizes a network of interbreeding across lineages.

Unresolved Questions and Future Discoveries

Stringer outlines open questions including why modern humans survived while other hominins did not, how widespread Denisovans were, and what genetic exchanges imply about adaptation to high altitude and cold climates. He also notes exciting new fossils such as Denisova 25 and a potential third Yukhan cranium that could test prior conclusions, and stresses the need to integrate morphological and genetic data for a coherent tree.