gedankenexperiment: human races
(posted by Angelica)
What would the world be like now if the human race was split into two distinct groups and kept evolving? It almost happened, say this article
The genetic split in Africa resulted in distinct populations that lived in isolation for as much as 100,000 years, the scientists say.
This could have been caused by arid conditions driving a wedge between humans in eastern and southern Africa.
It’s fascinating to contemplate what could have occurred. Would one race eventually rise dominant and vanquish the other? Or would they co-exist somehow and somehow continue to roughly their equivalent of this point in our history? Would people from the two groups fall in love and if so, would societal sanctions on such parings be considered moral? Racism, after all, would be quite sensible if the races were actually different.
This sort of findings affirm my belief as a moral relativist. After all, our very existence in our current form as human beings is such an unlikely accident. If things have turned out just slightly differently, our lives, societal organization, cognitive activities, mating rituals might all be radically different. It’s hard for me to fathom faith in absolutes when it seems we are created in chaos.
Tags: evolution, gedankenexperiment, human nature, moral relativism, science
May 12th, 2008 at 9:15 pm
But it is “racism,” if we are actually contemplating two distinct species? My understanding is that, say, Neanderthal is not the same species as every Homo sapien — black, white, Asiatic or whatever — today. Barack Obama, Hillary Clinton and John Yoo — whatever their ideological differences — all have much more in common with any nearest evolutionary relative past or present, because all three are Homo sapien.
May 12th, 2008 at 10:18 pm
I’m going to assume that Angelica is using the word “human” to refer to the species “sapien”, rather than the genus “homo”. Ian Tattersall has written a terrific book about the various species of humans that once roamed the planet (where “human” refers to the genus).
For obvious reasons, the history of humans is more controversial than the history of, say, whales or lions. Tattersall argues that, more than most other narratives put together by biologists, the history of humans (or rather, the interpretation of the human fossil record) was influenced by political factors. A hundred years ago the tendency was to build a narrative whereby humans evolved in a straight path to their current peak (sapien). Tattersall points out that all other genuses of animals have ancestries that look like like a complicated tree, with many branches that lead to extinction, but for some reason it was unpopular to look honestly at the evidence that suggested that humans, too, had developed many species that had gone extinct. There has been a tendency to classify any abberant human fossils as belonging to the species homo erectus. For most other kinds of animals, abberant fossils are assumed to indicate a possibly new species. But, for a long time, the human fossil record was subject to different rules. Tattersall is very critical of this practice. He argues that if humans were any other species, to be examined by biologists objectively, then the concensus would favor the idea that there was a great diversity of human species, all of whom went extinct, except for our own species. I think at one point he suggests that 43 different species of humans could be seen in the fossil record, if the fossil record was read in such a way as to favor a theory of many species.
In an article he once published in the magazine Scientific American, Tattersall argued that modern homo sapience probably emerged in Africa about 200,000 years ago. They probably left Africa more than 150,000 years ago. Because of a volcano in Indonesia that buried some people and fossilized them, we know that modern homo sapiens had reached Indonesia by 78,000 years ago.
Given these dates, the article that Angelica is looking at seems to be talking about a split among homo sapiens. But such findings should not be surprising. Rather, it is normal for species to branch, and for most of the branches to go extinct.
I especially relate to the sense of wonder regarding what it would be like to see several human species living together. Apparently that did happen, a little over a million years ago, around Lake Victoria. That was a long time before homo sapiens came on the scene, but there were at least 4 different human species whose remains have been found in the area at roughly that time. Of course, Our methods of dating fossils leaves enough margin at error that we can never be sure that thte different species were actually at the lake at the same time.
As to the question “Would people from the two groups fall in love” my sense is that, by definition, the answer has to be “no”. I could be wrong about this, but I’m under the impression that a species is largely defined in terms of its members ability to be sexually attracted to one another. This is one reason why all dogs are considered one species, despite the dramatically different breeds in the world - dogs from different breeds are able to be sexually attracted to one another. There are exceptions to the rule, I’m sure.
May 12th, 2008 at 10:29 pm
jackson: I assumed that when Angelica or anyone speaks of “races” –a term with definition difficulties — she means various members of the same species. Is it even scientifically coherent to speak of differences in “races” at the genus level? (That is not a rhetorical question — I don’t think it is coherent, but I could be wrong.)
May 12th, 2008 at 11:32 pm
Mona, I was responding mostly to “if the human race was split into two distinct groups and kept evolving”. If a species splits into 2 distinct groups, and both groups keep evolving, you soon have 2 separate species. That was the idea I was riffing on. Since I recently read Tattersall’s book, I also threw in a bit of the history that he covers, a look back at the era when many human species walked the planet.
May 13th, 2008 at 1:08 am
Harry Turtledove had an interesting alt history, A Different Flesh, in which Homo Erectus had crossed the Bering Straits and populated the Western Hemisphere, and the European colonists enslaved them shortly after they first made contact. At some point in the late 20th century, because of animal rights activism, slavery and medical experimentation was outlawed and they were granted a lower grade of citizenship.
May 13th, 2008 at 3:08 am
Mona,
Whether it’s “racism” or “specie-ism” is semantics. The idea that fascinates me is that, had things gone a little differently, we could be living in a world with different types of intelligent creatures rather than just one.
I think a lot of moral absolutism is predicated on maintaining human exceptionalism. That is why Darwin’s ideas were so shocking in his day (still is in some circles, I guess). The idea that the bright line between human and animal can be blurred shocked the religion-based moral foundation of the time.
As Jackson’s comment pointed out, even in the field of post-Darwin biology, the human species is still treated as an exceptional case and where-ever possible, the researchers couched the narrative of human evolution as a linear descent rather than the tangled web it probably was.
Jackson,
Thanks for the detailed comment. A lot of that stuff wasn’t really on my radar.
As to the question “Would people from the two groups fall in love” my sense is that, by definition, the answer has to be “no”. I could be wrong about this, but I’m under the impression that a species is largely defined in terms of its members ability to be sexually attracted to one another.
You’re talking to somebody who grew up on Star Trek. To me, being from different planets is not necessarily impediment to falling in love.
Kevin Carson,
What would really be interesting would be an alt-history in which we are the unterspecies.
May 13th, 2008 at 6:41 am
There has been some studies finding that Neanderthals and Homo Sapiens “inter-bred”.
See:
“The major point is that Neanderthals and modern humans were probably interfertile and most likely interbred - and that we would then have picked up most favorable Neanderthal alleles. Which may have something to do with the cultural ‘ big bang’ that happened not long after.”
See isteve and PaleoJournal.
May 13th, 2008 at 8:45 am
Just to mention that another reason why the human fossil record is controversial is that there isn’t actually much of it - as recently evolved large animals living on land in dry, warm conditions, we humans are really bad at getting fossilised. Had we only stuck to the bottoms of ponds, our fossil heritage would be secure. Boring, but secure.
May 13th, 2008 at 9:20 am
This sort of findings affirm my belief as a moral relativist.
And it was only a week or so ago that I commented about how remarkable it is that agree with you on so many things, Angelica.
I simply don’t understand this view that you’re calling “moral relativism.”
If we ever meet again, we will have to have a long meta-ethical discussion over Midori sours.
May 13th, 2008 at 9:20 am
Mona,
Ken Macleod’s Engines of Light series includes a multiple hominid angle in which the species are at least intellectually equal. It turns out there’s a pocket of human-settled worlds many light years away at the end of an artificial wormhole, and that the star systems of the pocket were colonized with Earth species by a super-advanced alien civilization.
Actually, the alien civilization first genetically altered squids (the Kraken) and bipedal dinosaurs to intelligence. The Kraken, with their complex neural systems, became the super-intelligent navigators of FTL ships visiting much of the galaxy, swimming in their enormous reservoirs of water inside the ships (some Herbert influence, obviously), and the saurs piloted them and did planetside work. Subsequently the Kraken and saurs did the same sort of genetic tweaking of the hominids, and engineered three sentient species: humans, an intelligent pithecantropus, and an intelligent gigantopithecus. All three coexisted in the pocket of colonized worlds at the end of the wormhole.
May 13th, 2008 at 9:53 am
Brock,
Hey, last time I made it out to Memphis. Maybe next time it’s time for you to come to Taipei. Oh, and any out of town AOTP reader who find themselves in Taipei, email to apply for your free beer at El toro.
May 13th, 2008 at 10:28 am
Most evolutionary trees are bushes, and alternate between rough equilibrium and rapid change. They might have less than one million years of rapid change, and then several million years of relative stasis.
Of course the same pattern can’t occur over small scales and large scales. If things alternated between rapid change and stasis on scales of hundreds of thousands of years, then they would average out to gradual change on scales of millions of years. Because things alternate over millions of years, they don’t show this pattern over hundreds of thousands of years.
The same logic applies to the bush. If you look at the whole bush, you see many different branches; if you look at one branch, you see many different twigs. But if you look at one twig, it is one twig.
At some point, you are dealing with one species, or one lineage, and you are not getting any smaller branches.
The debate should rest on evidence, and not on analogies to other scales. The evidence has been debated and is still being debated. There are some who argue that the MT DNA evidence excludes most multiregional continuity, and there are some who argue that it does not - either challenging the calibration or the whole approach. I’m inclined to distrust the approach because of built-in lineage loss.
May 13th, 2008 at 10:43 am
It seems pretty interesting to note that early theories of human evolution proposed a very very early split between apes and humans, with all of the apes on one side and humans and our ancestors on another. Some even argued for an earlier split, in which apes and monkeys were entirely separated from humans. We now know that chimps and bonobos are closer to use than the rest of the apes, but despite the chance in knowing how closely related we are to the great apes, and learning more about their cognition, their legal status has barely changed.
May 13th, 2008 at 10:51 am
““we would then have picked up most favorable Neanderthal alleles. Which may have something to do with the cultural ‘ big bang’ that happened not long after.””
That idea is Euro-centric to the core. Aborigenes in Australia were painting beautiful cave paintings 30,000 years ago. They clearly didn’t inherit any genes from European Neanderthals.
May 13th, 2008 at 11:28 am
Marja, I’m not clear which approach it is that you distrust. Multi-lineage or a single straight line?
May 13th, 2008 at 1:39 pm
I could have sworn I had a comment here. It linked to some Ernst Mayr.
May 13th, 2008 at 9:27 pm
Angelica: Apologies for my having gone into pedantic mode. This is, indeed, interesting stuff. And I agree:
May 14th, 2008 at 10:29 am
I distrust the interpretation of the mitochondrial and Y-chromosome DNA evidence to support out-of-Africa II.
Very crudely put:
Out-of-Africa II regards the older regional populations, particularly in Europe, east Asia, and Sundaland, as distinct species, and argues that modern Homo sapiens wiped them out.
Multiregional continuity regards some older regional populations as subspecies of Homo sapiens, with continuous gene flow between regional populations. Of course some local populations could diverge at the species level; H. florensis is probably distinct at that level.
May 14th, 2008 at 10:56 am
Marja, you believe some of the older human populations interbred with homo sapiens, as sapiens expanded across the world? What is the evidence for believing that interbreeding occurred?
May 14th, 2008 at 12:22 pm
Sorry if this is somewhat disorganized.
I used to follow the debate in depth. However, it has been years since I’ve had ready access to the literature.
I must object to your framing. An absolute burden of proof is anti-rational; a relative burden of proof emerges when one theory corresponds with other facts and/or other rationally-accepted theories, and another theory does not. We are unlikely to find direct evidence for many of these things, and we will depend on indirect evidence, e.g.:
The prevalence of shovel-shaped incisors in east Asian populations, both before and after the supposed replacement. This could represent convergent evolution.
The fact that any given population of H. sapiens sapiens is equally interfertile with every other population of H. sapiens sapiens. If two populations diverge into two species, they will have reduced interfertility before they have no interfertility; moreover, if several intermediate populations exist, the extreme ends may have reduced (or no) interfertility with each other while remaining interfertile with the intermediate populations (i.e. ring speciation). If 12,000 years of relative, not complete, isolation have no discernible effect on interfertility of the relatively isolated populations with other populations, then it requires either comparable timespans with far tighter isolation or far longer timespans with comparable isolation. (I don’t think old world gatherer-hunter populations were ever that isolated.)
Many of these *relatively* isolated populations have lost blood types. If ALL modern humans have gone through as tight genetic bottlenecks as these populations, let alone tighter genetic bottlenecks, then ALL modern humans should have lost more blood types. My understanding is that we have more blood types than any other great ape species, and most if not all the blood type of the other great ape species, but I could be wrong.
The (reasonable) attempts to calibrate the mitochondrial DNA studies using the then-accepted dates for the arrival of humans in Australia and the Americas; now-accepted dates for the Americas are far earlier.
The (inherent) flaws of the mitochondrial and Y-chromosome DNA studies, that they lose half the ancestors in each generation. This doesn’t affect large populations over short periods, but seriously screws with small populations over short periods and may have similar problems with large populations over long periods.
If you have enough genetic bottlenecking for the different populations to speciate, then you have too much genetic bottlenecking for the mitochondrial evidence to be worth anything at all.
May 14th, 2008 at 3:54 pm
Marja, thanks. You make a good case against the mitochondrial evidence. However, I’m not sure disproving mitochondrial evidence is the same as arguing for the multi-regional origins of the modern sapien population. For me, the main argument against the multi-regional origins of the modern sapien population is the fact that even populations that have been long isolated, such as the Australian Aborigines, seem to be as sapien as any other human now alive. I’d expect more variety if homo sapiens, as they spread across the Earth, interbred with Neanderthals in Europe and homo erectus in Asia.
May 14th, 2008 at 6:05 pm
Multiregional continuity holds that the regional populations were the same species all along (with mutations which increased brain size spreading from any one population to every other population). Out of Africa II (or the replacement side of it) holds that the regional populations were different species.
OoA II holds that regional populations speciate more quickly, or with less isolation, MRC holds that they speciate more slowly, or with more isolation. I guess that OoA II “predicts” fewer physical differences, but greater reproductive barriers, than MRC.
May 14th, 2008 at 6:15 pm
Anyway, while I’m skeptical of the mitochondrial DNA evidence, I may be too dismissive of it. I’d like to find more sources on the mitochondrial evidence, the calibrations, whether lineage loss really matters in large populations, etc.
I’m reading Evowiki about this right now:
http://wiki.cotch.net/index.php/Out_of_Africa
May 14th, 2008 at 6:49 pm
Marja, thanks. I’m puzzled by the line “regional populations were the same species all along”. It seems to raise the question, all over again, of when humans left Africa.
Thanks for the link to the evolutionary wiki. That looks quite interesting.
May 14th, 2008 at 9:22 pm
Members of genus Homo first left Africa about 2.0-1.8 million years ago. These were Homo ergaster/early Homo erectus.
Again, let’s consider ring species. At one end of the ring, you have one population, and a the other end, you have another population, which are not interfertile with each ther; but in between, you have several successively-interfertile populations.
It’s doubtful that the earliest H. ergaster/early H. erectus would be interfertile with late H. erectus, late H. neanderthalensis, or present-day H. sapiens sapiens.
If we add the time dimension, genus Homo is like one ring species, with H. ergaster leading back towards H. habilis and/or H. rudolfensis.
According to OoA II, you have one set of intermediates leading to late H. erectus (and perhaps H. florensis), another leading to H. neanderthalensis, and another leading to H. sapiens sapiens (with these three branches, and others, diverging far enough to be separate species at the ends).
According to MRC, you would have the same intermediates, but less divergence. So in both examples the “ring species” has one end at 2.0 million years ago, but one says it has several mutually-isolated ends at 0.1 million years ago, and the other says it has one highly-regionally-variable end at 0.1 million years ago (of course there is one rather uniform end at 58 years After Present).
If we go back to the original subject, MRC basically sees partial isolation, and then renewed gene flow, as the norm; OoA sees full-scale isolation, speciation, and replacement as the norm. The example is an example of the MRC-type situation in Africa, but if the genetic evidence does show traces of this having happened in Africa, and won’t show traces of this happening elsewhere, that would speak for OoA II everywhere else.
It also depends what the relative populations were in Africa and in the rest of the world, in the lower and middle Paleolithic. In MRC, the largest regional populations in the past would usually make the largest genetic contribution to the present.