I have a couple of quick questions.
It is my understanding that you believe the number of individuals in the human line has never dipped below several thousand, since the human-chimp split. Is that your view?
You believe that Homo erectus was the first true human. You might want to have a look at this paper:
(The acheulean handaxe: More like a bird's song than a beatles' tune?)
Briefly, the authors argue against the commonly received view that the techniques for producing Acheulean handaxes were acquired by social learning and that handaxes are therefore cultural. They argue that language need not have been involved in showing another individual how to make them.
Finally, they write: "A further problem facing the cultural transmission hypothesis is the much more rapid pace of change after Acheulean handaxes disappeared at 300‐200 Ka. If the behaviors involved in the production of both handaxes and post‐Acheulean artifacts were culturally learned, how do we explain this very marked increase in the speed of change?"
I should add that the average brain size of Homo ergaster / erectus specimens in Africa, dating from 1.8 to 1.5 million years ago, is a mere 863 cubic centimeters, while that of Georgian specimens of Homo ergaster / erectus (also known as Homo georgicus) dating from 1.8 to 1.7 million years ago is even lower, at 686 cubic centimeters (see the chart by Susan C. Antón and J. Josh Snodgrass, from Origins and Evolution of Genus Homo: New Perspectives, in Current Anthropology, Vol. 53, No. S6, “Human Biology and the Origins of Homo,” December 2012, pp. S479-S496). By comparison, the brain size of early Homo specimens (excluding 1470 man) is 629 cubic centimeters. These fall well outside the modern human range. Also, there is no evidence for a sudden jump in brain size from Australopithecus afarensis (whose average brain size was 478 cubic centimeters) to Homo ergaster / erectus. The brain size of early Homo (who lived around 2.3 million years ago) is intermediate between the two.
It seems that the first unambiguous signs of cultural transmission in the human fossil record don't appear until about 300,000 years ago - by which time there were three species of rational human beings: Homo sapiens (who emerged around then), Neandertal man and Denisovan man (who was presumably rational). This is troubling, as recent analyses suggest these species diverged around 800,000 years ago, long before the advent of human culture. So, did God ensoul three distinct species of hominins?
I'd like to ask you about your suggestion that Adam may have been a genealogical common ancestor of all living humans, who lived only a few thousand years ago. What do you make of this article?
"What's particularly fascinating about this is that we in the present day can actually change who our most recent common ancestor was. After all, the estimate that the MRCA lived only two or three millennia ago, long after humans became isolated on far distant continents, only works because of the globalization of the last 500 years. The theory is that enough European explorers intermarried with the various indigenous populations of the places they colonized so that, over time, even the most isolated groups become linked into the overall family tree.
"This is a controversial theory, particularly since there are still thought to be a handful of uncontacted groups in South America and southwest Asia. If these peoples - each group of which only numbers about two hundred or so - really have remained completely cut off from other humans for millennia, then that would force the most recent common ancestor back to the Upper Paleolithic, anywhere from 40,000 to 10,000 years ago.
"We can at least say this: in 2011, it's possible but not proven that the MRCA dates back to a surprisingly recent date, anywhere from 8,000 to 2,000 years ago. In 1511, before European exploration had really begun in earnest, the MRCA was still unquestionably an individual who lived in the Upper Paleolithic. And, by 2511, the current trends in globalization suggest that everyone will definitely share a recent MRCA...and one that gets more recent with each passing generation as more and more lineages mix."
Is the author right here, in your opinion?
I look forward to hearing everyone's answers. Cheers.