No, the particular mutation found in European originated long after the ancestors of Europeans left Africa. It did not originate in Africa. This idea is simply wrong.
No, but TV documentaries are a terrible source for scientific information. They frequently get it garbled or just plain wrong. (I say this having worked on and been interviewed for a number of TV shows on scientific topics. In fact, one of my present duties is developing new TV shows about scientific research.)
I’m a professional Ph.D. biologist with 35 years experience. I work closely with molecular geneticists and have collaborated with them on papers analyzing DNA, including the descriptions of several new species. Molecular genetics is one of the leading fields at my scientific institution, and I regularly attend seminars on cutting-edge research in the field.
What do you mean by a “DNA scientist,” exactly?
I’ve read the original scientific papers that detail the genetics involved. I have come to the conclusion I posted based on those scientific papers.
There aren’t enough rolleyes available for someone who is sure that they are experts on a topic after having watched one TV show.
I have no idea what you are trying to convey with this. Human populations outside of Africa carry Neanderthal genes they picked up by interbreeding with them. That’s no longer controversial. (In my personal opinion, because hybridization was limited in space and time, this means Neanderthals were a separate species rather than a subspecies.)
Of course it doesn’t. There are a number of scientific publications on the issue, not just that one.
That wasn’t a case of the mama fooling around with a white guy. The baby is too pale.
I saw an interview with a playwright from an Indian Reserve in northern Canada. (Thomson Hiway?) He’d written a fairly provocative play about life on a remote reserve; he discussed among other issues, that one of the characters was nicknamed “nigger” as in “Nigger Sam”. He said that there was a quite visible variation in skin tone even in a small, relatively isolated reserve with a small gene pool, not all of it directly hereditary. (Meaning, I assume, that variation happened from generation to generation - which in the context of this thread, suggests a limited number of pigmentation genes) Those who ended up darker were often treated badly, partly a local trait and possibly also something picked up from white north American culture.
Neanderthals (Homo sapiens neanderthalensis) are humans, and presumably had dark skin before migrating to Europe and becoming a distinct subspecies.
In fact, the Indian subcontinent, like the entire continuum from Western Catai to the Levant, is a mix of haplotypes due to trade, intermarriage, and the rise and fall of various empires that at different times spanned significant portions of Central Eurasia. While there are some fairly distinct striations of haplotype groupings between castes, the idea that India overall can be considered in any way a homogenous grouping is patently absurd. As John Mace stated earlier, the content of melanin in the skin accorded people in Africa a selective advantage (not just in skin color but the eye) at the cost of having to produce melanin, which is an advantage that is not necessary at higher latitudes where the sun is less intense and the climate is typically more cloudy. Europeans and Asians (as a general population, irrespective of supposed racial grouping) tend to demonstrated greater neoteny in features; that is, they are more childlike in appearance, including lighter skin, eye color, et cetera, indicating that the loss of pigmentation is a regression (in the sense of limiting development of features to an earlier stage in the development cycle, not “less evolved”). In other words, as populations moved from Africa into Eurasia and became distinct, they tended to favor phenotypes that were not fully developed because they did not provide a significant advantage. Sexual selection, as discussed by Blake, may be a significant contributor to this, but it could also just be a random mutation amplified by founder effects i.e. the high rate at which particular genotypes can be propagated through a bottlenecked population, just as red hair and green eyes are. Such changes in a population do not need to offer significant selective advantages; they just need to be propagated with sufficient frequency that they become distinct. One can see similar effects among any population that has been dominated by one or two familial lines for more than a few generations; everybody starts to display certain features because they all have some degree of interrelation. And this can occur over just a few generations; of the span of many centuries it is easy to understand how populations can be come visually distinct even though they have no practical evolutionary advantage.
Aboriginal Americans are distinct because they had a very tight bottleneck; the total population of paleoamerican ancestors may have been no more than a few hundred people in clans of a few dozen each, likely already fairly closely related. Even with this, there is a wide variation in adult height, skin pigmentation, and appearance between natives across North America to South America. Again, founder effects will cause features in derived but isolated populations to dominate and become distinct from the source population.
Stranger
Most scientists still classify Neanderthals a different species, *H. neanderthalensis *
I’m a lumper, myself, and would gladly see them repositioned as a sub-species, but the taxonomic community is very conservative.
And we now haveDNA from the famous Spanish site Sima de los Huesos (Pit of the Bones), showing Neanderthal ancestors in Europe at ~ 400K years ago. That fits in well with the generally thought of 500K - 600K years ago split between our lineages.
Actually the taxonomic community has changed its opinions on what constitutes a species significantly during my own career. The more conservative view is that Neanderthals were a subspecies, while its revisionists today that see them as a separate species (which was the view before they were classified as subspecies).
The distinction between species and subspecies is necessarily somewhat arbitrary. It also depends on the species concept one is using.
It used to be that under the Biological Species Concept, any hybridization was regarded as indicating that two forms belonged to the same species. More recently, it has been recognized that two forms can be regarded as separate species even if they hybridize in nature, as long as there are significant barriers to gene flow and hybrids are limited in space and time.
Hybridization between sapiens and neanderthalensis seems to have been limited to a narrow window of time in the Middle East, just as sapiens left Africa. Hybridization does not seem to have occurred over the time the two forms co-existed in Europe or elsewhere, or if it did it has not left a genetic signature. In my book, because hybridization was limited it indicates the two forms were good species, at least at the same level as Gray Wolves and Coyotes, which also hybridize in the wild.
I guess it depends on when you start the clock. H. neanderthalensis predates H. sapiens neanderthalensis, but you have to go back to the 19th century for that. I do remember, growing up, that the pendulum would swing back and forth a few times, as Neanderthals were seen more like us, then less like us. In the 1960s, subspecies status was often claimed. But once Out of Africa became consensus, species status seemed appropriate again. Now we’re confronted with interbreeding, but like you say, that seems to have been fairly limited.
The first humans were not black.
Neanderthal genes occur in African populations, too, but via backflow, not direct interbreeding.
…
And how did they not all die out from melanomas, then?
We exist to kick ass and chew bubble gum. And we are all out of bubble gum.
Seriously though, I have to get ready for work and didnt’ read the whole thread.
It has to do with (among other things I’m sure) balances of folic acid & vitamin D. The level of melanin in your skin means that sunlight causes one to go up while another goes down.
Interesting conjecture here - what we would look like if early humans were not able to wander from Africa. What if there was no Sinai and the continent was surrounded by water? Humans would not have been able to leave until the advent of watercraft, which is fairly recent, meaning we’d all probably look a lot more alike?
Possibly, possibly not.
The extremes in most traits is found within Africa, with extra African traits falling squarely within the range of what is found in Africa. So it’s just as possible that we’d end up looking even *less *like each other.
Really, if you remove the extra-African populations all you lose is the absolute palest of skin colours. All the other traits exist within Africa.
Think about it for a second, where in the world would the you find a trait that can’t be found in a Berber, a Khoi or a Kenyan? So if people were trapped in Africa, we’d pretty much look like Africans do in our world, which is far more diverse than people outside Africa.
But the Berbers are descendants of people who left Africa and then came back. No?
The vitamin D thing is weird to me. I accept it, but it seems so strange that it would both be so hard to get enough of (ironically, since I’ve been diagnosed with a severe deficiency I got prescribed industrial strength supplements for), and that it would be so easy to die from it (or at least make you unable to breed).
Though I didn’t know that it causes Rickets and other bone softening diseases. Still, it seems like it should be hard to be that undersupplied with something our bodies can literally synthesize. And yet apparently it’s really common in developing countries. Still, what makes vitamin D so hard to get enough of?
Depends what you’re thinking of. The best example maybe would be the original inhabitants of the Americas. There’s a moderate amount of variation, but generally they are mostly descendant from a small gene pool that started from Siberia 20,000 years ago.
If we couldn’t leave until, say, 3,000 years ago then maybe there’s be an admixture; more likely, one group nearest the Persian Coast in that hypothetical would be the source population that would quickly spread across the rest of the world. Current thought seems to be that it didn’t take long for the length of the Americas to be initially populated; even travelling/expanding 10 miles further each year, 12,000 miles would be covered in 1200 years. Once that first group is established, the odds another group would displace them is unlikely, barring a major tech advance such as agriculture or better weapons. So you still have the single group/limited variation problem. the only difference might be if the migration only happened a few thousand years ago, we’d probably still be black.
The Australians aboriginals arrived 40,000 to 50,000 years ago and their arrival needed a certain amount of fairly significant ocean travel, so even back then boat technology was fairly solid. On theory is that
Given that melanomas generally arise after people have reproduced, there is no reason they would cause a population to “die out.”
We don’t know when humans became as relatively hairless as they are now. Like chimps, early humans could have had pale skin but have been protected from sun by thicker hair.
Do they? Well, scratch that, then.
One current line of thinkingis around 1.2 Ma.
Possibly, but that should show up as a gene change, no?
I’m not aware that the gene responsible for the shift from pale skin in chimps to dark skin in early humans has been identified. This article suggests that the gene for hairlessness in the human lineage goes back 6 million years, but I don’t know how widely accepted that is.