Monday, December 23, 2019

Youngest Homo Erectus Remains Are About 100,000 Years Old

This reaffirms the paradigm and status quo, that Homo erectus had a million year run in Asia and vanished shortly (percentage-wise) before modern humans arrived.

Razib reminds us that there were many archaic hominin species in Asia contemporaneously with Homo erectus, including Neanderthals, Denisovans, the "hobbits" of Flores, and an additional species or three in the Philippines and possible China too. Modern humans reached Sumatra no later than 70,000 years ago, immediately after the Toba eruption.

It wouldn't be surprising to find new Homo erectus remains later, or new modern human remains earlier, that would narrow the gap between the two species or possible leave evidence of a brief overlap like the 1,000 years overlaps characteristic of Europe at a local level.

This species diversity may have flowed from topographies and ecologies that created many separate and independent ecological micro-niches that could not be sustained, for example, on a broad flat plain or in an area with thin trees cover and rolling hills.

My personal conjecture is that the Toba eruption resulted in temporary ecological changes that devastated the already low density H. erectus population and cleared the way for an influx of modern humans from South Asia via Myanmar. Modern humans eventually killed almost all of the stragglers, although relict populations of H. erectus may have survived many thousands or tens of thousands of years past first contact and I don't rule out the possibility that there is still a small relict population of archaic hominins or archaic hominin hybrids deep in some Indonesian jungle. If archaic hominins continue to exist anywhere, it is probably there.  
Homo erectus is the founding early hominin species of Island Southeast Asia, and reached Java (Indonesia) more than 1.5 million years ago. Twelve H. erectus calvaria (skull caps) and two tibiae (lower leg bones) were discovered from a bone bed located about 20 m above the Solo River at Ngandong (Central Java) between 1931 and 1933, and are of the youngest, most-advanced form of H. erectus. Despite the importance of the Ngandong fossils, the relationship between the fossils, terrace fill and ages have been heavily debated. 
Here, to resolve the age of the Ngandong evidence, we use Bayesian modelling of 52 radiometric age estimates to establish—to our knowledge—the first robust chronology at regional, valley and local scales. We used uranium-series dating of speleothems to constrain regional landscape evolution; luminescence, 40argon/39argon (40Ar/39Ar) and uranium-series dating to constrain the sequence of terrace evolution; and applied uranium-series and uranium series–electron-spin resonance (US–ESR) dating to non-human fossils to directly date our re-excavation of Ngandong.
We show that at least by 500 thousand years ago (ka) the Solo River was diverted into the Kendeng Hills, and that it formed the Solo terrace sequence between 316 and 31 ka and the Ngandong terrace between about 140 and 92 ka. Non-human fossils recovered during the re-excavation of Ngandong date to between 109 and 106 ka (uranium-series minimum) and 134 and 118 ka (US–ESR), with modelled ages of 117 to 108 thousand years (kyr) for the H. erectus bone bed, which accumulated during flood conditions These results negate the extreme ages that have been proposed for the site and solidify Ngandong as the last known occurrence of this long-lived species.
Yan Rizal, et al., "Last appearance of Homo erectus at Ngandong, Java, 117,000–108,000 years ago" Nature (December 18, 2019). doi:10.1038/s41586-019-1863-2

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