Saturday, September 30, 2017

Did Humans Become a Distinct Species 350, 000 Years Ago?

The hits just keep on coming.  On the heels of the discovery in Morocco, at Jebel Irhoud, of a skull with some modern characteristics dated to 315 thousand years ago, we now have a genetic study that proposes that our species emerged between 350 and 260 thousand years ago.  How did a genetic study reveal this?  Science News reports:
The trick was retrieving a complete version of the ancient boy’s DNA from his skeleton to compare with DNA from people today and from Stone Age Neandertals and Denisovans. Previously documented migrations of West African farmers to East Africa around 2,000 years ago, and then to southern Africa around 1,500 years ago, reshaped Africans’ genetics — and obscured ancient ancestry patterns — more than has been known, the researchers report online September 28 in Science.
The ancient boy’s DNA was not affected by those migrations. As a result, it provides the best benchmark so far for gauging when Homo sapiens originated in Africa, evolutionary geneticist Carina Schlebusch of Uppsala University in Sweden and her colleagues conclude.
In line with the new genetically derived age estimate for human origins, another team has proposed that approximately 300,000-year-old fossils found in northwestern Africa belonged to H. sapiens (SN: 7/8/17, p. 6). Some researchers suspect a skull from South Africa’s Florisbad site, dated to around 260,000 years ago, qualifies as H. sapiens. But investigators often place our species’ origins close to 200,000 years ago (SN: 2/26/05, p. 141). There is broad consensus that several fossils from that time represent H. sapiens.
What is important to understand is that we have the fossils from Herto and Omo that date to between 150 and 200 thousand but that does not mean that is the earliest time that our species may have actually showed up. The Jebel Irhoud material is only partly modern—in the face mostly—and we do not know how the genetics for this population would look. It is possible that, as some investigators are saying, the Jebel Irhoud material represents the earliest fossil representation of our clade and that over the next 100 thousand years, the modern form fully evolved.   

1 comment:

  1. Jim, from a logical perspective, recently they have confirmed 5.7 myo human footprints, or "highly likely" human footprints because of the uniqueness of the human foot. Logically that could be the print of a homo sapien and that would sure be a lot older than 300,000 years. Don't worry, I will understand if you don't want to publish my views we're used to such reactions. But I think my point is an important technicality, we were also told the Laetoli footprints belonged to pithecines (Afarensis wasn't it?) But it seems to me, inductively speaking, all human feet and all human footprints ever found in the present day world, have belonged to humans. It seems to me the most plausible explanation is that some species of human made that track dated at 5.7 million years. My question to you since yo are an evolutionary biologist, is this - at what stage do you stop "pushing back" evolution theory? For example they found pollen that indicate established clades, 100 million years out of place (ICR), they are finding things out of place all of the time. Why is there a scientific almost neurotic agreement that all of these push backs can't be evidence against evolution given that we would expect such evidence to exist if macro evolution had not occurred? We would expect the predictions to fail. Now technically you may say that pushing back evolution is at least feasible. Fine, but why pretend this isn't the type of evidence we would expect had evolution not occurred? That breaks the law of non-contradiction, for we would of course expect macro evolution to be broken in it's patterns and predictions, had it not happened.