I was reading the wiki article on human skin color a while back and I came upon this:
So when our ancestors lost their hair they had light skin, but of course at that time they were not us. I’m not sure at what stage in the genus homo we began to spread out from Africa to Europe and Asia, wiki kind of made me think it was homo habilis. So would a fair statement if we’re going with homo sapien as us, that several races emerged at the same time?
Maybe some Dopers have some expertize in this area.
I am not an expert, but it is really not possible that the ancestors of today’s humans radiated from Africa as anything but Homo sap. It is certainly possible (certain, in fact, read about Java man) that H. habilis or something like it, left Africa, but parallel evolution is not possible, so there must have been some movement out of Africa of H. sapiens. The best evidence suggests that H. sapiens left Africa between 200,000 and 300,000 years ago.
I read recently (in the last couple weeks in fact, but I don’t recall where) that light skin may have evolved in Europe no more than 5000-10,000 years ago. That suggests that the selection pressure for being able to produce your own vitamin D must have been intense.
This raises an interesting question that just occurred to me this minute. We must have been speaking when we left Africa, since no human race lacks speech. Yet that depends on several physical mutations (in the mouth and throat) as well as unknown cognitive mutations. Yet linguists speculate that fully human speech started only 50,000 years ago. The same reasoning says that is impossible.
Why can’t language develop seperatly?
There were several migrations out of Africa, the first being at least 1.7M years ago (based on fossils found in the Republic of Georgia). It is generally thought that this was some form of H. erectus, but the Georgian fossils contain some surprisingly primitive features more common to H. habilis.
However, it is thought that all these populations outside Africa died out at some point without contributing to the extant population of H. sapiens, and that all non-African populations are descended from a small population that left Africa about 60k years ago (+/-).
By the time of this dispersal, it is thought that our ancestors had dark skin, although maybe not as dark as most African populations today. It may have been more like what you see in the Bushmen-- medium brown. Lighter skin is thought to have evolved at least twice after we left Africa-- once in N. Europe and once in N. Asia.
This is all conjecture (educated guess), though, so keep in mind that we have no direct evidence of what skin color our ancestor were.
No. 60k years ago at the latest, and maybe even closer to 50k.
There seems to have been some earlier migration of H. sapiens into the Levant (around 100k years ago), but it is thought that that population either retreated back to Africa, or died out.
That timeframe is consistent with the Out of Africa hypothesis. And don’t get too hung up on the 50k years. Not only is it an estimate based on a number of unproven assumptions, but it probably has some significant error bars associated with it.
It is uncertain where exactly in Africa modern Homo sapiens first evolved. Present populations on the continent vary from light brown to very dark brown. The oldest lineages that exist today vary: the Khoisan of South Africa are fairly light brown, while the pygmies of Central Africa are very dark brown. Their coloration is correlated with latitude, the Khoisan being mostly temperate in distribution, the pygmies tropical. Because of this, they may tell us little about the coloration of ancestral populations.
Ancestral Homo sapiens in Africa were almost certainly not as pale skinned as chimpanzees or modern Europeans, but beyond that it is impossible to say. The most likely route for the populations that spread out of Africa was through the Middle East. They would most likely have been medium brown, like modern populations in the area today.
Your numbers are wrong. Humans didn’t begin leaving Africa (that’s a troublesome statement, “left Africa” … obviously, many people stayed) until 70-50K years ago. The safe bet is that modern human speech–and probably modern cognition–evolved around the same time as the migrations.
While it’s not completely and utterly out of the realm of possibility, it’s close. Speech functions identically in all human populations, and while there are local variants in how we hear certain sounds, that’s due to training at a very young age picking up minute variations based on certain lingual patterns. They can be learned as an adult, but it takes a lot longer. It seems highly unlikely that something as basic as speech evolved simultaneously among seperate populations.
Most human features can be clearly stated to have developed before or after the migratiosn away from central Africa. The more cosmetic and variable they are, the later they developed. The more rigid and universal, the earlier.
bump*
From Not The Bible