Human beings - the 'default' model.

[peter]

If you take all the various breeds of dog from great danes down to chihuahuas, and allow them to freely interbreed, they gradually revert back toward the basic Canis lupus familiaris type from whence all the common varieties were created [by man] via selective breeding. [As an aside, apparently most current breeds of dog we enjoy now, were in existence as far back as roman times demonstrating how early in our history we got to grips with the idea of modifying form by the carefull selection of breeding partners from which offspring are produced.] The best approximation of this form is that of the so called pariah dog [or pi dog] which looks almost like a dingo with a trace of hyena thrown in.

I wondered, is there a sort of human equivalent to the pi dog that would result from a free interbreeding of all the current human types, and if so, any ideas as to what he/she might look like? Would the form of this individual reproduce the earliest human type before any sepparation into the current 'races' [if that word has any true meaning] or have the ensuing genetic changes in the human population of what, the last hundred or so thousand years, been such that the genetic information as to the appearence of this early basic form, has been lost.

[lorin]

I don't think there could ever be a default model of the human race because technology has interfered with evolution. A default model of a human would have excellent eye sight because the default model (DM) would have only bred people with excellent eye sight, those with bad eyes (me included) having been unable to hunt or protect ourselves, would have died. The DM would have been more disease free because those with perhaps a cancer gene would have not had the opportunity to reproduce.

In order to have a true DM you would have to remove all technical, medical, and educational advantages we have. Also remove all racism that would prevent the races from intermingling.

[Zarathustra]

In one sense, you're right, Lorin. Cancer is largely a phenomenon we see because humans live long enough to get it, thanks to our technology. When people died at 35 or 40, they didn't live long enough to get cancer, even if they had the gene for it. But on the other hand, that means the genes were there all along, being passed down but not expressed. So it is technology that allows this to happen, but genetically we wouldn't have been different in that respect.

I'm not sure about the other examples, either. Not everyone is a hunter in a hunter/gatherer society. Lots of people stay home to tend the fire, make tools, and care for the babies (i.e. women), and you didn't need the senses or strength of a hunter to do that. Even in very early hunter/gatherer societies, there was division of labor and reciprocal altruism that would have led to weaker genes getting passed down. There are signs of even Neanderthals caring for their injured, nursing them back to health after breaking legs, etc. I'm sure there were people with bad eyesight long before the invention of glasses.

But on the other-other hand (running out of hands here ) it is again technology that makes this possible. People think of "technology" in terms of computers and cars, but the hand axe and the spear were far more important inventions at their time. Mankind's ability to take advantage of non-zerosum relationships has always been driven by the possibilities made available by the invention of tools. Without spears and handaxe, there would be no mammoth or giraffe to share with a tribe ... in other words, no surplus that encouraged reciprocal altruism that leads weaker members to have a better chance of surviving.

But back to the original question ... humans didn't come from an "original" form. There were dozens of different kinds of humans, many of whom interbred. For instance, we can't eliminate the Neanderthal from our genes in the way Peter is suggesting. Nor would it make sense to try, because which one was our "original" form? Sure, our Neanderthal portion is less than the Homo sapiens sapiens majority, but each was in itself "original." And we didn't get this diversity through selective breeding for specific traits. Neanderthal genes are entirely new genes that some humans don't have (Africans, for instance).

I thought all domesticated dogs came from wolves. ??

[Hashi Lebwohl]

For all our supposed "differences" there is a very small diversity in the human gene pool at this time. No, it isn't so small that we risk the sort of species damage facing cheetahs but you can take any random male in the world, pair him with a random female, and they can produce a viable child. I have seen some research tracking backwards in time through mitochondrial DNA that shows a sort of "bottleneck" at about 70,000 years ago (thereabouts); this date coincides with a known supervolcano eruption and so the thinking is that many humans died out as a result of it, meaning that every person alive today ultimately came from the leftovers who managed to survive. This, also, explains the relative lack of diversity, differences in skin tone, hair type, and body type notwithstanding.

As far as I can tell, from what research I have seen, we have changed almost not at all for the entire length of recorded history. We could take a resident from some settlement 12,000 years ago, bring them forward to today, and based on physical appearance we wouldn't be able to identify the temporal transplant. Only through conversation--once the linguistic barriers have been overcome--could we determine that this person is out of time based on their cultural and scientific knowledge.

No one will ever willingly carry out selective breeding of humans for specific traits. To do so would be to engage in eugenics and that "science" has an extremely poor history associated with it.

[Vraith]

I don't believe free, random interbreeding among dogs would ever bring them back to something like the Adam of Dogs...even if such a creature ever existed.

[BTW, Piers Anthony did it with people in a book called "Macroscope."...bred them back together and got super-people.]

Don't think that would work on dogs, or on peeps either...we mix everything together now, we'd get, for instance, a caramel-ish skin color...but our earliest common were very unlikely to be that light.

Also, height...I don't think any amount of mixing of modern humans would make us shorter again. [partly it is nutrition is better, or course, but in pretty much every people shortness has been selected against.

Lots of other stuff, too. Plus, the average person has something like 40+ mutated genes.

We would, and dogs would, likely regress toward some means...but the "means" that exist in our genes are not the same as they once were...we won't go back.

[all that being said, there's less difference than peeps think...many of which don't much matter cuz of our technological environment.]

As an aside...the "average life" of 40 is a bit misleading...early on and recently quite a lot of folk lived to 60+...the average is low cuz so many died so young. But if you made it to the mid-teens, you had a pretty good chance to make it to 60. [in the middle years, when we first started getting crowded, things were probably more problematic..but I've never seen actual numbers on that].

[lorin]

I was on Craigs List looking to adopt another dog. There was an ad for pups. This guys female Mastiff had mated with his male Yorkie. Would have loved to have seen how that action worked and the pups must have been quite a sight. (Not that his has anything to do with Peter's post)

[Obi-Wan Nihilo]

Post pics if you find any lorin.

Recent discoveries have cast doubt on the idea that the out of Africa theory is the full story. Indeed genetic studies indicate the introduction of regional human variants into the a.m.h. genome. Most Europeans have some percentage of Neanderthal genes, Asians have Denisovan genes, and some Africans have genes deriving from an as yet un-discovered line of paleohuman. Evidently these genes are more likely to relate to appearance than other traits. So I'm not sure that there really is a default model of human.

[Vraith]

Recent discoveries have cast doubt on the idea that the out of Africa theory is the full story.

yea, it's getting complicated. my surface consolidation of the trails I've seen is that main/dominant lines do, indeed come out of Africa. But they do so more than once...and when they do, they do something related to what peter was asking about...they mix back in with descendants of previous migratory outbursts. [[IIRC, Denisovans might not be as purely Asian as previously suggested...that was the "center" of their line, but I'm pretty sure there're findings as far west as Spain or Portugal.]]
The bottleneck mentioned previously is highly debatable...but if it DID happen, it is one reasonable factor for re-integration of cousins.

[I'm Murrin]

Yeah, some recent research suggests a lot of european features (pale skin, red hair, some eye colours, iirc) actually came from interbreeding with Neanderthals, which separates out Europeans from Africans (for example) pretty distinctly.

[peter]

Fair point about the wolf Z. Canis lupus familiaris [the domestic dog] is indeed a sub species of Canis lupus [the gray wolf], but to what degree the separation had occured prior to the domestication of the dog is {I think} pretty unclear. I think I have mixed two ideas here in this thread - the idea that different forms of the same species tend, historically to have descended from a common form, and the second, that if mixed back together, these current forms would take us back to something like that orignal form. [I fully accept both ideas I may have got entierly wrong and it could all be bullshit .] The theory of evolution by natural selection would seem to imply that in seeing the sepparation into breeds, races, and sub-species that develop from a single species over time, we are witnessing the genesis of tomorrows new species in the process. That a particular 'phenotype' [of course with variation, but of a general type] would be seen to emerge if all the worlds races were equally mixed by random interbreeding seems fairly sure I would think, and one would believe that in an increasingly cosmopolitan world we would have to be moving closer to the point where that would occur. [A situation akin to all of our domestic breeds of dog, of a sudden, being able to select their mates without our inteference.] I'm just interested really in what form such an individual might take.

[re Lorin's tale - My father told me that in one of the veterinary practices in which he was employed, a male chihuahua impregnated a female irish wolf hound thrugh the holes in a weld-mesh sepparating wall between two runs; such are the forces that drive the urge to reproduce when 'the time is right' in natures creatures!]

[peter]

As I undestand it there are three basic human types - negroid, mongaloid and caucasian. The introduction of Neanderthal features would I'm guessing have to have been after this 'tri-form' division had occured [or would it?]

[I'm Murrin]

Not so much a straightforward division. You had other hominids in Asia (eg the Denisovans) and Europe (like Neanderthals) early on, the first waves of Homo Sapiens spread out of Africa, interbred with other hominids, adapted to the new climates, then more African humans came out and interbred with the earlier waves. All over millions of years so there was all kinds of adaptation and evolution going on in the different regions.

(And even more complex than that: For example the Denisovans who inhabited Asia were heavily interbred with Neanderthals.)

[peter]

But all of these were still 'human beings' [ie Homo sapiens members] and there intermixing would be not much different than some of the more pysically separated kinds of human extant today getting together and producing [fertile] offspring.

Do I understand Murrin, that the Devonsian and Neanderthal lines are still [genetically] represented in todays human genome [meaning also that the Homo sapiens sapiens genome of {what} 100,000 years ago would have shown some considerable difference from that elucidated today by the 'Human Genome Project'.

[Obi-Wan Nihilo]

There is also a third paleohuman mixed in the genome of sub-Saharan Africans, that is known only through genetic evidence. By paleohuman I mean a human species distinct from anatomically modern humans, but with some ability to interbreed. The work of Luigi Luca Cavalli-Sforza on the more general subject of human inter-relatedness has established the existence of 7 basic lines of a.m.h., of which all 7 are represented in Africa but every other non-African human appears to have branched off a single one of those lines. It's never that simple and of course there was and is intermixing, but those are the general population trends. And it speaks loudly of a common African origin, with some regional caveats.

[I'm Murrin]

The issue is that you're not just remixing a single set of genes, you're having new mutations and old genes dying out, such that your idea of blending them all back together and arriving at a "default" doesn't work.

As for current genome: Modern humans have some Neanderthal DNA, with Europeans having a higher proportion. There's a notable amount of Denisovan DNA in aboriginal Australians and some other parts of Australasia.

[Obi-Wan Nihilo]

There is also a third paleohuman mixed in the genome of sub-Saharan Africans, that is known only through genetic evidence. By paleohuman I mean a human species distinct from anatomically modern humans, but with some ability to interbreed. The work of Luigi Luca Cavalli-Sforza on the more general subject of human inter-relatedness has established the existence of 7 basic lines of a.m.h., of which all 7 are represented in Africa but every other human appears to have branched off a single one of those lines. It's never that simple and of course there was and is intermixing, but those are the general population trends. And it speaks loudly of a common African origin, with some regional caveats.

[Vraith]

The issue is that you're not just remixing a single set of genes, you're having new mutations and old genes dying out, such that your idea of blending them all back together and arriving at a "default" doesn't work.

Exactly. so...peter you berk re-mixing WON'T "re-evolve" us back into something closer to the original...I think I said that already?...here's a new way to think of it, in case a number or two impress you?
Ignore the Denisovans, and Neand's and/or any others that might be discovered that also mixed. Take just the 3 groups you mentioned.
Now, assume that the distinction happened instantly/spontaneously one day [say a Friday when everyone was way too drunk...a prehistoric St. Patrick's day, they all woke up Saturday wondering where their pants were, and 2/3rds of them were wondering what happened to their skin color...some freaky tattoo-bath??...]
And let's consider the day as being a mere 50,000 years ago.
Since that day, there have been, absolute bare minimum 3 TRILLION mutations in the human genome. [a more likely number is 10 times that]
Now, the amount that is UN-changed is god only knows how much bigger than the number of changes, there will be much resemblance...but still, there is no going back.
If you really want to get as close as possible to the original...find a currently existing tribe in the boonies of Africa with the least amount of interaction with outsiders. THEY are the most similar to the original...not any re-integration of the migrators.

[Obi-Wan Nihilo]

It's interesting that most of the surviving genome of Neanderthals resides in the appearance while precious few Neanderthal genes persist in the reproductive areas of the genome, showing that cross fertility was problematic, but that the appearance traits had their uses (being, as it were, environmentally adapted over a much longer time horizon).

[peter]

Yes, I did grasp that re-mixing won't bring us back to a 'historical' proto-human type [I refer my learned friends to my original post ] but I equally contend that a random mixing of the currently found genetic allele's that go into making up all the different types of physical atribute visible in the various 'races' today, would likely produce a human appearance somewhat different to that which we commonly see; I for one could only guess what such a group of individuals might look like! [I refer my learned friends to my 2nd post ]

The limited information I could find relating to the '3 Major Races of Man' [Masatoshi Nei; Proffesor of Biology Pennsylvania State University] suggested that the common ancester to todays caucasiod/mongaloid races diverged from the ancestor of todays negroid peoples some 110[ish] thousand years ago. The caucasoid/mongaloid divergence seems to have occured somewhat later at around 40[ish] thousand years. Would it be correct to assume that the [for example] Neanderthal mixing would have occured after the first divergence but perhaps before the second.

Also the 'interbreeding' aspect used always to be a problem [IIRC] years ago because of the very real difficulty of defining what actually constitutes a species. The 'litmus test' at that time, on which the classification of two individuals of being the same species was that [obviously in the normal condition] they would be able to produce fertile progeny. On this definition any [even pre-anatomically modern] human capable of interbreeding with anatomically modern humans would [by definition] be of the species Homo sapiens .

[Obi-Wan Nihilo]

That is not true, peter, as there are some species that can interbreed with only limited success or occasional fertile offspring. This seems to have been the case with Neanderthal to human breeding.