So my multigenerational ships each crash land leaving relatively few survivors of each group with just enough resources to barely survive and maintain their modest numbers for n generations in divergently but equally hostile environments … each enough to survive in but some with higher than our ideal O2, some lower, different gravities, different food sources, different predator threats, etc. … pretty ideal speciation circumstances. How many generations until speciation?
If it takes that long, it’s hard to imagine it ever happening again on planet Earth. I think even in the most dire post-apocalyptic scenario, where a few scattered groups of humans are left, our curiosity and intelligence as a species is such that well within 100,000 years we would have built ships and located one another.
Put another way, Earth is too small a habitat (given human behavior) for additional speciation of humans to occur.
Meaning that space travel (as mentioned by DSeid) may be the only prospect for speciation.
The evidence is circumstantial but in sum is pretty persuasive, and comes in three parts. First, the indigenous populations of Australia that are not distinctly Papuan or Polynesian in linguistic systems also lack several of the common genetic markers found in in virtually all Polynesian populations. Second, the Pama-Nyungan languages that are spoken by all cultures except the northeastern part of Australia are both closely related in grammar and distinct from any other known language or proto-language grouping. This argues that these cultures did not experience any significant degree of external trade or cultural exchange. The areas in the North that are known to have have significant trade with the Papuans have a language base that is distinctly Papuan in character and specifically shares commonalities with the Trans–New Guinean language family. Third, prior to Polynesian blue water navigation (somewhere between 2000 and 3000 BCE) there just wasn’t any way for the majority of populations in Australia to be exposed to other cultures outside of Australia with any degree of regularity. There is no evidence of a pre-Polynesian Melanesian or Indonesian culture having developed the techniques for blue water navigation.
How the Aboriginals migrated to Australia a topic of debate, but I believe the consensus is that they travelled via land bridge from New Guinea via the exposed Sahul shelf. Credible evidence exists to support human habitation from 50,000 to 60,000 BCE, although whether the indigenous people are the direct inheritors of those people or descendants of a mixture of later pre-Paupan peoples is unknown and probably unknowable. We do know that the Aboriginal Australians (except for the groups mentioned above) do not appear to be genetically close to the Papuan peoples.
Agreed, although even identified subspecies of animals are often oblivious to “behavioral barriers” and other non-geological mechanisms. The concept of subspecies is really most useful to make distinctions between populations, and is often applied based upon epigenetic distinctions rather than clear differences in the genome. The various subspecies of brown bear (Ursus horribils) are all capable of interbreeding, and when they do their offspring are fertile and fall into a similar type of continuum of size, coloration, et cetera as humans. This is even moreso the case for the American Black Bear (Ursus americanus) which has a wide range of epigenetic variation but has a sufficiently diverse and intermixed gene pool that making subspecies distinctions is really subjective. Speciation in humans, on the firm basis of not being able to produce a viable offspring, is probably in the hundreds of thousands of generations or few millions of years, which is comparable to speciation intervals in other great apes.
Stranger
I think that’s a pretty reasonable conclusion. This assumes that we don’t genetically engineer ourselves into non-interbreeding populations.
Can you cite the genetic studies you’re referring to? I’m genuinely interested in reading them.
You lost me there. I’ve not seen to the concept of epigenetics tied to the concept of a subspecies before.
The two most closely related great ape species are Chimps and Bonobos, which are thought to have diverged about 2M years ago. However, they do not occur in the same geographic location and are known to produce fertile hybrids in captivity.
Other than that, you’ve got humans and chimps/bonobos which diverged about 5-6M years ago. There is some evidence that there were two divergences, one at 10M years and then a reuniting at about 6M years after which we split for good, but I’m not sure if that’s the consensus view yet. We assume humans and chimps aren’t interfertile, but we really don’t know for sure. We get a “humanzee” thread on this MB at least once a year, as I’m sure you know.
Not necessarily: there are to this day indigenous populations which are hostile to outsiders and are left alone. I’m thinking particularly of the Andaman Islanders. If we continue to leave them alone then they may well diverge from mainstream humanity.
The likelihood that the will be left “alone” for ~1M years is essentially nil.
Y-chromosome studies tell an interesting story. The aborigines are mostly of C4 haplogroup, which is found only in Australia, but there’s a small percentage of a rare strain of R. Since the R haplogroup developed relatively recently, and now dominates Europe (R1b1b and R1a), and is also found in Central and Southwest Asia (R1a, etc.), Northern India (R1a), Southern India (R2) and West Central Africa (R1b1a), as well as the early spinoff to Australia (R1* ?), there must be a fascinating story of prehistory waiting to be deciphered.
On another note, I recall reading that Australian aborigines have been theorized (by physical features?) to include pre-sapiens genes. (I don’t have a cite, nor know whether that study had any validity.)
Doesn’t everyone have pre-sapiens genes?
They’ve been left alone for 70000 years so far.
That sounds like something out of the 1950s, unless it was the recent genetic data indicated non-African populations to have some very small admixture of non-sapiens genes (Neanderthals in Europe and possibly even Erectus in South Asia).
I assume he meant admixture of sapiens populations with non-sapiens populations.
Any admixture we have would not be with “pre-sapiens” as they would have to be extant for us to mix with them. If we found a population of H. erectus surviving today, it would be incorrect to call them “pre-sapiens”.
Of course, something like 98% of our genes could be considered to have come from “pre-sapiens” since we share those with chimps and therefore they must have come from our pre-sapien ancestors.
I don’t see what your point is. Are you saying that it is at all likely they will be left alone for the next 1,000,000 years?
I don’t know, if I was a pygmy [whatever the current PC name is for them] female, and one of my hulking 2 meter tall viking gamer buddies was makign eyes at me, I would run far far away from them…I can not imagine an unassisted survivable birth between a 3 foot tall woman and a man twice her size. Sort of like a female tea cup poodle and a great dane.
Homo Erectus was still present in SE Asia until 50K years ago, wasn’t it? There’s Homo Floresiensis and Homo Erectus Soloensis for two. So it’s quite possible that just as Homo Sapiens expanding into Europe possibly - I believe that the jury is still out - interbred with Homo Neandertalensis, so Homo Sapiens could possibly have interbred with Homo Erectus. A genetic study would be fascinating.
There’s some evidence that Australia was colonized via a series of migrations, the most recent perhaps 6,000 years ago. I am not sure what the current state of play is with genetic data on this.
But the teacup poodle and the great Dane don’t have to mate directly to be the same species, either. The poodle might, for instance, mate with a beagle, and the beagle might mate with a German shepherd, and the German shepherd might mate with the great Dane. So you could still get Dane genes into a poodle population, and vice-versa, over the course of generations. Likewise, you could get Viking genes into a pygmy population through a similar process (though probably not as convoluted, since humans aren’t nearly as varied in size as dogs).
I wasn’t talking about “hopeful monsters”. I was talking about genes/genetic changes that create genetic isolation between those that have it and those that don’t.
For example, I mentioned “a mutant X chromosome that kills standard human male embryos”; that can spread easily because it out competes its normal X chromosome competitors by producing more females. A gene doesn’t need to be advantageous to its host to succeed, especially in the short run; it just needs to out compete its rivals. And if a new strain of Y chromosome happens to appear that can resist the killing effect then it in turn will spread rapidly since it has no competition with other Y chromosomes among the “new X” females. That apparently has occurred repeatedly throughout evolutionary history. If in one case the mutant Y also happened to make breeding with “old X” females difficult to impossible, you’d have a situation where genetic incompatibly with the old population exists, paving the way for eventual speciation.
Or another example. Suppose a small isolated settlement gets hit by an endemic disease that produces male sterility, except for one man who has a genetic resistance to the effect. He’s still infected, just fertile. The later generations of the settlement are all descended from him, and they all both have the gene and are infected. If outsiders show up, they not only can’t have children with them but are sterilized themselves; the settlement people have become a separate breeding population.
As I said, this is a pretty rare means of speciation.
Cite that this commonly occurs in speciation?
Such scenarios, while possible, are not typical causes of speciation.
Actually it is fairly well established that the population of H. sapiens that left Africa did indeed interbreed with H. neandertalis. See here for a discussion about it.
It totally fails to persudae me.
Why would anybody expect Aborigines have Polynesian markers? Why not also note that they lack Norwegian markers?
This evidence might be persuasive if they lacked Malesian markers, since any contact would have come through Indo-Malaysia. But the fact that they lack Polynesian markers is every bit as meaningful as the fact that they lack Eskimo markers.
Which is proof positive that the methodology is hopelessly flawed. We know for a fact the the Aborigines of Northern Australia did experience any significant degree of external trade or cultural exchange for centuries, and we know that some trade occurred at least for millennia. We know this from borrow words in languages, from written records and from genetic evidence.
The fact that language structure doesn’t provide any evidence of this well established interchange simply proves that language structure is not s a useful tool for detecting interchange. That is hardly persuasive evidence that interchange never took place.
Some areas in the North East that were settled by Papuans have Pauan languages. Meanwhile adjoining groups have distinct non-Papuan languages. This is not indicative of any absence of interchange via Malesia. It is just indicative of a lack of settlement by Malesian peoples.
Well yes, there is. We know that the dingo was taken to Australia ~5, 000 years ago.
There is no consensus on that. The stretch of water between Indonesia and New Guinea would have been extremely dicey when sea levels were lower. Hell, it’s dicey today, and tides today don’t rush between the Pacific and Indian oceans through such a small opening. The route form Timor to the mainland is only a few kilometres longer than the route to New Guinea, and is much calmer water. So arguments can be made for either option.
We know that the people of the Top End have a significant admixture of Malay genes. What we don’t know is how long that interchange has been occurring. But there is no doubt that Australians were an admixture with other races since before European contact.
Once again, this is proof positive that the technique does not work. We know, by your own admission, that Papuans regularly had contact with the mainland. We know that interbreeding occurs. Yet aside from " the groups mentioned above", we can find no evidence for this interchange using this methodology.
Which proves that even if Australia were regularly visited by people from all over the world, we would not expect to find any evidence of it using this methodology.