Homo sapiens and Their Cousins

[Recusant]

I haven't counted the re-clicks, but testify that there were many. Got to "reply" and now dare to add to the thread. Will Ctrl-C before I hit "post" because the electronic pixies may have to battle the database gremlins for a while, potentially losing the actual content in the process. It's not just you. 

These folks are proposing to overthrow the current timeline of the development of our species and its connection to close relatives. Previously a date of approximately 300,000 years ago has been given as the time at which Homo sapiens were sufficiently differentiated from previous Homo (and similar enough to the modern examples) to be considered early members of our species. If the conclusion proposed below is correct the date could get pushed back to around 1,000,000 years ago. Significant if true sort of thing. Beware the enthusiastic headline editor.

"A Million-Year-Old Skull Just Rewrote The Origin Story of Humanity" | Science Alert

An ancient skull, warped and damaged by the ravages of time and degradation, may have just altered our understanding of the history of modern humans.

Using careful 3D scanning and digital reconstruction techniques, a team of researchers from China and the UK has rebuilt the damaged artifact, discovering exactly where it fits on the hominid family tree.

It's not the skull of a modern human ancestor, but that of a closely related human. Even so, its age pushes back the timeline for the divergence between the ancestor of Homo sapiens and its close relatives, suggesting that the origin of our species is several hundred thousand years older than we thought it was.

Two skulls, known as Yunxian 1 and Yunxian 2 (sometimes catalogued as EV 9001 and EV 9002), date back to around a million years ago.

Their survival at all is somewhat miraculous – few hominid remains of that vintage exist on the fossil record. However, time and fossilization are not kind, and the skulls were discovered (in 1989 and 1990, respectively) heavily damaged and distorted.

This made identifying their position on the hominid family tree particularly challenging. They were given the placeholder name "Yunxian Man" after the contemporaneous name of the district in which they were found.

However, in the decades since the skulls were excavated from the calcareous rock in which they had lain for millennia, archaeological tools have improved dramatically. Now, to study a fossil, scientists don't have to damage it further; instead, they can conduct high-resolution 3D scanning and perform their analysis using digital tools.

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Interestingly, this analysis revealed that the skull has a mixture of both older and newer traits. It has a thick brow ridge and a long, low braincase, characteristics also seen in earlier hominids, such as Homo erectus. The base of its skull is broad, and its forehead is flat.

On the other hand, it also exhibits traits seen in later hominids. The size of its braincase was larger than that of Homo erectus (although still smaller than that of Homo neanderthalensis or Homo sapiens). It also lacks the strongly angled rear skull region seen in Homo erectus, and the shape of its face is flatter.

This mixture of traits suggests that the Yunxian Man is a link between Homo erectus, which came before, and the hominid species that were yet to come. The researchers believe that it fits in the Homo longi clade, a sister group to Homo sapiens, and the lineage to which the Denisovans are thought to belong.

[Continues . . .]

There is an older article/blog post linked which gives a decent overview of a particular version of the timeline that may be severely modified (again, if their conclusions are borne out).

"Understanding the 'Muddle in the Middle'-Hominins from the Pleistocene" | World of Paleoanthropology

The paper is open access:

"The phylogenetic position of the Yunxian cranium elucidates the origin of Homo longi and the Denisovans" |  Science

Abstract:

Diverse forms of Homo coexisted during the Middle Pleistocene. Whether these fossil humans represent different species or clades is debated. The ~1-million-year-old Yunxian 2 fossil from China is important for understanding the cladogenesis of Homo and the origin of Homo sapiens.

In this study, we restored and reconstructed the distorted Yunxian 2 cranium using recently introduced technology. The results show that this cranium displays mosaic primitive and derived features. Morphometric and phylogenetic analyses suggest that it is an early member of the Asian H. longi clade, which includes the Denisovans and is the main part of the sister group to the H. sapiens clade.

Both the H. sapiens and H. longi clades have deep roots extending beyond the Middle Pleistocene and probably experienced rapid early diversification. Yunxian 2 may preserve transitional features close to the origins of the two clades.