Friday, 26 January 2018

Modern Humans May Have Left Africa 200,000 Years Ago

This ancient jawbone suggests our species left Africa 40,000 years earlier than expected | Science | AAAS

The story of when and where modern humans first left Africa is continuing to develop and looks like becoming more complicated than first thought when the evidence seemed to point to a single migration by a small group around 50,000 years ago.

A large international team led by Israel Hershkovitz from Tel Aviv University have concluded that the jaw bone found in a Misliya Cave on the western slope of Mount Carmel in Israel is that of a Homo sapiens, but that it is between 177,000 and 194,000 years old. This is some 40,000 years earlier than modern humans were believed to have left Africa to begin their world-wide dispersal. The previous earliest H. sapiens remains were those found nearby in the Skhul Cave on Mount Carmel and Qafzeh Cave in Israel, dated to between 80,000 to 120,000 years old.

The fossilised hemimaxilla with several teeth in situ had characteristics of modern humans and none of those of Neanderthals. It was closely associated with thousands of stone tools and animal remains. The stone tools were made using the sophisticated 'Levallois' technique normally associated with modern humans.

The team published their findings today in Science:

To date, the earliest modern human fossils found outside of Africa are dated to around 90,000 to 120,000 years ago at the Levantine sites of Skhul and Qafzeh. A maxilla and associated dentition recently discovered at Misliya Cave, Israel, was dated to 177,000 to 194,000 years ago, suggesting that members of the Homo sapiens clade left Africa earlier than previously thought. This finding changes our view on modern human dispersal and is consistent with recent genetic studies, which have posited the possibility of an earlier dispersal of Homo sapiens around 220,000 years ago. The Misliya maxilla is associated with full-fledged Levallois technology in the Levant, suggesting that the emergence of this technology is linked to the appearance of Homo sapiens in the region, as has been documented in Africa.

Click to enlarge
They used three independent numerical dating methods - U-series (U-Th), combined uranium series and electron spin resonance (US-ESR) series, and thermoluminescence (TL) — carried out in three different dating laboratories. These yielded consistent results.
  1. Nine different measurements of burned tools dated by thermoluminescence gave a mean age of 179 thousand years (ky). This is consistent with other Levallois tools found elsewhere in Isreal.
  2. Crust adhering directly to the maxilla using U-Th analyses gave at least 185 ky while the same technique on dentine gave only 70.2 KY
  3. Enamel of the same tooth analysed by combined US-ESR dating, gave 174 ky.
However, these dates are not without their critics. As the Science article by Ann Gibbons, accompanying the paper points out:

The dates on the tools seem solid, dating experts say. But several question the dates on the fossil itself, partly because the authors write that the jawbone was scanned using computerized tomography three times, and the x-rays could have influenced the amount of radiation trapped in the tooth enamel, skewing the luminescence dates. Uranium dating expert Alistair Pike of the University of Southampton in the United Kingdom notes that a crust on the jawbone “is heavily contaminated by detritus.” The contamination could bias the radiometric dates on the crust, which includes a younger date of 70,000, says geochronologist Warren Sharp of the Berkeley Geochronology Center in California. He and others also note that relying on nearby tools is problematic, because it’s possible that the bone was mixed into the tool-bearing layer later in time.

Lavalois technique for flint knapping

Source: Wikipedia
Credit: José-Manuel Benito Álvarez,
CC BY-SA 2.5, Link
The slightly dubious thing about these dates is that dentine, which should be the best protected part of the fossil against contamination, gave an age of only 70 KY.

Even if these dates prove correct this doesn't necessarily mean that all modern non-African peoples are descended from these early migrations of course. Migrations could have occurred several times when the climate was suitable, only to retreat again when the climate changed again, or they could even have become locally extinct. Given that there are no physical barriers in terms of impassible mountain ranges, expanses of water or (at times) wide deserts, there would be nothing to prevent hunter-gatherers with no livestock from migrating by coastal spread alone.

The more significant point is perhaps, if this finding is conformed, that our species may have evolved earlier than was thought since if we were in the Levant 200,000 years ago, it is unlikely that we are only 300,000 years old.

What will be interesting is how the creation industry reacts to this find. The standard response is to claim the fossil is not human, not old, fake, bad science and/or, when all else fails, not in agreement with the Bible therefore wrong.

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