Regarding human evolution, there is an issue that has always fascinated me and I turn to you to humbly ask for your almighty guidance. I’ve read accounts that say the original human-ish creatures came out of Africa and spread around the world, and that it took approxiamtely 100,000 years or so (please clarify) to get to the point we are now with the wonderfully wide variety of humans we have today. I don’t mean the more pedantic stuff like skin colors or average heights, but more the physiological stuff. Things like the ability to withstand cold (Inuit), the ability to live in high-altitude, low-oxygen environments (Inca, Nepalese), things like that. My question is, how long do you think it would have taken, assuming there was no interbreeding, before we had true speciation? And, taking that to the other extreme, is it possible that the human race will, due to modern mixing and interbreeding, return to the point where we are all indistiguishable from each other, physically or physiologically? Will we ever look like the above-ground civilization shown in the movie The Time Machine (the remake)? How long would that take? The Ernman is dying to know, thank you.
Depending on how you define humanish, it took a lot longer than that. Anatomically modern humans seem to have been around for over 200, 000 years, and creatures that would pass for modern humans on casual inspection have been around for over a million.
Skin colour *is *physiological stuff. It’s every bit as vital to survival as an ability to withstand cold or tolerate low oxygen levels. Skin colour isn’t just cosmetic.
That’s very hard to say.
In other species speciation derives initially from a lack of interest in breeding, rather than from any inability to breed. The two species simply cease to find each other attractive and thus cease to mingle. That then allows for further genetic separation which eventually results in genetic incompatibility. For example, jackals and wolves are perfectly *capable *of breeding with each other, but female wolves just don’t find male jackals to be attractive, and female jackals don’t find wolves attractive.
The thing about humans is that the species, males especially, have proven track record of fucking anything that will stand still long enough. We are astonishingly non discriminatory in our sexual preferences. Male human also have a proven track record of rape, so female preferences have little effect on preventing miscegenation. Because of this propensity for miscegenation, two human groups would need to become genetically isolated *before *they could be considered species, and that takes a damn long time. As a general rule of thumb you need a minimum of ten million years genetic isolation before two species become genetically incompatible. Humans, with their extremely long lifespans, would probably need four to five times longer than that.
So if we had to take an educated guess we would need to allow 40 million years of complete isolation before two groups of humans diverged into separate species. What is interesting about those figures is that humans and chips have been genetically isolated for much less time than that, only about 15 million years. This strongly suggest that humans and chimps may well still retain interfertility. The lack of hybrids between our species is very likely to stem from a lack of mating, enforced by the extreme strength disparity between human males and female chimps and the use of weapons b human. Those sorts of factors may be able to enforce mate selection isolation between two human groups, resulting in speciation without genetic isolation, but it’s hard to see how such could evolve in less than 5 million years or so.
Of course all of this is just rule- of-thumb. It’s perfectly possible for an isolated population to become genetically incompatible in just a few hundred years, it’s just staggeringly unlikely. It’s likewise possible for species to retain genetic compatibility after billions of years of isolation, but once gain staggeringly unlikely.
No. That can’t happen just through intermingling. Populations may cease to be distinguishable, but individuals will always remain individuals. Yo produce individuals that are even fairly similar would require an extreme bottleneck where the entire species was descended from just half a dozen individuals.
Humans haven’t been “speciated”. We never were and will never be “indistinguishable” from each other. The examples you gave, are not real examples of physiological differences due to natural selection. The Inca and Nepalese don’t have any special genetic adaptations for high altitudes. The same goes for the Inuit and cold. None of those groups of people have lived in those places long enough.
Ah, cite? I mean a real cite. Like an actual track record.
I know the concept that human sex evolved as forcible rape and/or self-preservative acquiescence to rape/ prostitution is a common theory, but I just have never been convinced.
There wasn’t just one modern human species. There were at least three and possibly more based on current evidence: homo sapiens, homo neanderthalensis and homo floresiensis. At least two of those interbred to produce a hybridized population that we see in Asian and European populations today. The sub-Saharan African populations that moved northward over thousands of years met up with a distinct human species: Neanderthals (there isn’t a great explanation of where they came from). They never wiped them out as thought until recently. Instead they interbred and hybridized. People of European or Asian descent have significant Neanderthal DNA 2 - 5%. Pure sub-Saharan populations don’t show any hybridization with Neanderthals.
Defining a species is mostly a man-made construct rather than a biological one. The concept isn’t nearly as clean as is defined in science books.
Of course they do. It is ridiculous to say that different human populations don’t have different morphology. Evolution can happen extremely rapidly under harsh conditions. I think you know that but that is a very different claim from being a different species which is a nebulous term at best even in the animal world.
Modern humans have proof that they can evolve incredibly rapidly. Look at our nearest relatives. It is a pretty big jump isn’t it?
True. In fact, depending on your view of speciation, the genetic evidence could suggest that modern humans and Neanderthals did in fact represent good biological species, even though they interbred.
Contrary to the way it is often represented, the Biological Species Concept does not require that two good species be incapable of breeding. It only requires that gene flow between two species be limited in space and/or time. (Exactly how limited it must be is again a matter of opinion.)
The genetic evidence indicates that modern humans interbred with Neanderthals only in the Middle East, immediately after they left Africa. Gene flow was limited, indicated by the small contribution of Neanderthals to the non-African modern genome. There is no evidence of later mixing, even though modern humans and Neanderthals co-existed for thousands of years in Europe. So Cro-Magnons and Neanderthals seem to have behaved as good biological species during this time (even though they almost surely could have produced hybrids).
It seems to make them highly resistant, if not entirely immune, to high altitude pulmonary and cerebral edema. Also less likely to have blood clots at extremely high altitudes, such as on Everest. Tibetan women are able to carry babies to full term at higher altitudes than non-Tibetans, and even at moderately high altitudes their babies tend to have a slightly heavier birthrate and fewer problems breathing thin air.
Of course, get them high enough (like on Everest) they still have problems. They can still show signs of altitude sickness. It’s just that their “death zone” starts a little higher up the mountains than it does for the rest of us.
Humans and chimps split about 6M years ago. I think your rule of thumb is off by at least a factor of 2 for large mammals, and more like an order of magnitude for other populations.
Interesting question. I think the best answer is “never”, unless we are reduced to a much, much smaller population. If you look at something as simple as eye color, there is no reason that the recessive genes will disappear from the population, so while blue eyes (for example) might become less frequent, they will continue to pop up even from people who do not themselves have blue eyes.
Eye colour is a bad example for differentiating populations. It just hasn’t been a factor in discrimination in the past. Plenty of whites do not have blue eyes.
Given the global village we now live in I believe that eventually the “racial” distinguishing characteristics we see today will disappear, but it will take a long long time. Racist countries , particularly in the far east will be the last holdout of the “racially pure”. Geography created differentiating morphology, and modern transportion and communication has overcome geography. We will come to a point where kinky hair in the general population will be viewed much like ginger hair is today in the white population.
Its now known that eastern USA wolves comingled with coyotes long ago and it was only discovered through DNA. They are pretty well indistinguishable from each other within the sub species.
I’m not even sure that reducing the species to a smaller population would do it in the long run, Mace.
As I recall there was a severe population bottleneck sometime between 70-100k ago (I’m prepared to be corrected on that). Given that event it seems that severe differences can occur in populations relatively quickly to account for the many and varied forms of humanity extant.