How Long until a serperate group becomes a different species

[Eternal_Freedom]

This is in connection with a story I'm working on at present.

Let us suppose that we took a large group of humans and settled them on another world. The group is large enough to maintain a healthy gene pool. There is contact but no interbreeding between these new humans and the original civilisation.

How long (in years or generations) would it take for the new group could be counted a separate species in the genus Homo?

[LaCroix]

Correct answer: Until they cannot interbreed any more...

Given the fact that some remote parts of the earth had groups of human isolated for multiple ten thousands of years (Australia, for example), and still there was interbreeding possible, this will take time. Just look at Africans and Asians, who are extremely far removed (according to migration theory) and have evolved distinct 'racial' features. Still,they can interbreed.

Given a 'normal' (earth-like) rate of mutation, you it would take several million years.

The genus Homo is around for about 2.5 million years, and the hominids were around for 18 million years, so that could be a kind of benchmark.

[SilverWingedSeraph]

Evolution to any substantial degree requires lots of time or environmental pressures. If certain traits are needed to survive and pass on your genes in an environment, evolution can happen very quickly, in the span of a handful of generations instead of thousands or millions of years. You'd be hard pressed to put humans in an environment that would force adaptation to that extent, as we're fairly well adapted to most environments, and we have tools to allow us to do things we normally couldn't.

The ability to interbreed isn't necessarily an indicator of speciation anyway. Homo Sapiens were able to interbreed with Homo Neanderthalensis, and they're typically considered a different species. There's some evidence we could have produced fertile offspring with even more distant relatives.

[Broomstick]

Given a 'normal' (earth-like) rate of mutation, you it would take several million years.

Actually.... probably not "millions". Particularly if the new planet's environment is sufficiently different as to drive some real selection because it's not just a matter of mutation rate, but how fast various genes might be eliminated from the gene pool. I'd say on the order of at least 100,000 years to 500,000 minimum.

Also, it's more than just whether two groups can interbreed at all - horses and donkeys are considered separate species, even if they can produce offspring. Ditto for lions and tigers.

H. Neanderthal is usually said to have arisen about 600,000 years ago. H. sapiens about 100,000 to 200,000 years ago. They are considered separate species, and while interbreeding may have occurred it was a rare thing, at least as far as leaving kids behind. So, no, you don't need millions of years, but you do seem to need a time span in the six digits of years.

[Eternal_Freedom]

Interesting. Well, in this story I'm writing the new world is Earth-like but not identical (it is further out in the habitable zone, so it's surface weather typically doesn't get above 15 degrees C.

There's also some amateur eugenics going on, with the "unfit" being weeded out (not exterminated, just encouraged not to breed,for the good of the species.

How much of an effect might that have?

[SCRawl]

Given a 'normal' (earth-like) rate of mutation, you it would take several million years.

Actually.... probably not "millions". Particularly if the new planet's environment is sufficiently different as to drive some real selection because it's not just a matter of mutation rate, but how fast various genes might be eliminated from the gene pool. I'd say on the order of at least 100,000 years to 500,000 minimum.

Also, it's more than just whether two groups can interbreed at all - horses and donkeys are considered separate species, even if they can produce offspring. Ditto for lions and tigers.

H. Neanderthal is usually said to have arisen about 600,000 years ago. H. sapiens about 100,000 to 200,000 years ago. They are considered separate species, and while interbreeding may have occurred it was a rare thing, at least as far as leaving kids behind. So, no, you don't need millions of years, but you do seem to need a time span in the six digits of years.

Nitpick: the usual standard is being able to produce fertile offspring, which is something your non-Homo examples can't do (with the exception of extremely rare events).

As for the neanderthal/sapien thing, they're considered different species because of their different morphology. We were apparently able to interbreed with them, as (according to a fairly recent study, dumbed down here in a Scientific American article) apparently a few percent of the DNA of non-Africans comes from our H.neanderthalensis ancestors. It could be argued that we aren't separate species at all, but different subspecies of H.sapiens.

With respect to the OP, there is no set number of generations that would get the job of speciation done. If they were to face the same selection pressures as the original colony, then it might never happen.

[Spoonist]

Interesting. Well, in this story I'm writing the new world is Earth-like but not identical (it is further out in the habitable zone, so it's surface weather typically doesn't get above 15 degrees C.

There's also some amateur eugenics going on, with the "unfit" being weeded out (not exterminated, just encouraged not to breed,for the good of the species.

How much of an effect might that have?

For speciation to occur that wouldn't be enough pressure at all. You'd have to select FOR as well as AGAINST ie you need to have new mutations and then wipe out all that does not have that mutation. Then rinse and repeat for a loooong time.

However as a writer you could always add something fantastic instead.

[Bakustra]

Species aren't really definable in terms of interfertility alone; gray wolves, dogs, and coyotes are all interfertile, but are considered distinct species because of morphological and behavioral differences that make it unlikely for them to reproduce with one another on a regular basis and which distinguish them clearly from one another. Ring species are networks of individual, closely-related species that are interfertile with their immediate neighbors but not with any other species in the network. "Species", as a concept, are fluid and not really definable. So your subspecies of humanity would probably become distinct once it was obviously morphologically or behaviorally differentiated from humanity as a whole, since they would be sexually isolated. And this could take very little time indeed, on biological time scales.

[Eternal_Freedom]

Would those timescales be around about 200 years? That's the time span between the seperation and the present, although if it needs to be longer I can write in that there was a great drive towards isolation preceeding the seperation.

How major would the behaviouraly differences be? And what would be the best way to show this?

[LaCroix]

Species aren't really definable in terms of interfertility alone; gray wolves, dogs, and coyotes are all interfertile, but are considered distinct species because of morphological and behavioral differences that make it unlikely for them to reproduce with one another on a regular basis and which distinguish them clearly from one another. Ring species are networks of individual, closely-related species that are interfertile with their immediate neighbors but not with any other species in the network. "Species", as a concept, are fluid and not really definable. So your subspecies of humanity would probably become distinct once it was obviously morphologically or behaviorally differentiated from humanity as a whole, since they would be sexually isolated. And this could take very little time indeed, on biological time scales.

Given the variety already given within the h. sapiens species, there must be a hell of a morphological or behavioural difference to make it count. We already have at least 3 major phenotypes which are clearly distinguishable, but still, I don't hear much noise about calling them the h. s. africanus, h.s orientalis and h.s oxxidentalis or whatever.

And behavioural differences are off the scale between individuals of h. sapiens.

Dogs, Wolves and coyotes are a taking the comparison a step too far. I refer to the fact that nobody would classify Chihuahuas as a different species than Irish Wolfhounds, although morphological differences make it unlikely for them to reproduce with one another on a regular basis and distinguish them clearly from one another.

[Simon_Jester]

If chihuahuas and Irish wolfhounds were wild, we might very well consider them different species- and they'd speciate further apart due to different selection pressures.

It's only because we can physically track back to the point where we started triggering artificial speciation that we think of them as being 'naturally' part of the same species.

[Ziggy Stardust]

Would those timescales be around about 200 years?

Absolutely not.

The problem with modern humans is that not only are we incredible adaptable from a biological standpoint, but how powerful our technology is. The fact that we can use tools to alleviate environmental discomforts immensely reduces the impact of selective pressure.

What you would need in order for speciation is both a very large time scale, as well as an environment in which technology is unable to completely eliminate certain factors. You have to think about forces like gravity, solar and cosmic radiation levels, atmosphere composition and density, nutrition, etc. etc.

On the other hand, adaptation =/= speciation. You can have things that differentiate the populations to a large extent that don't have an impact on their ability to reproduce. For example, a planet with lots of helium in the atmosphere (not so much as to be poisonous, or that they would need breathing apparatuses) would change the way they communicate. Beyond even the fact that their voices will be comically high, over time it would have a lot of tangible effects on language structure (not to mention physical stature ... breathing will be effected). And these are things that would operate on a much more reasonable time scale. A few hundred years in a uniquely different environment will have tremendous effects both physically and socially on the population.

EDIT: In fact, I would argue that the best way to approach a sci-fi story with this sort of setting is to FOCUS on the debate of whether or not the other human population are still human, due to these sorts of differences.

EDIT2: As for the eugenics thing, you have to be careful with that. Humans are very bad about deciding what constitutes a real advantage, as opposed to a superficial one. Why do you think purebred dog varieties have so many health problems? Genetics is so immensely complicated and interconnected that selecting even for traits you think would be universally helpful, such as size or better eyesight or whatever the hell you are thinking of, will have effects on other aspects of the human anatomy that might not be noticeable for thousands of years (and then everyone has sickle-cell anemia or something).

[Korto]

Which can make a damn good story of its own, some group using eugenics to select for what they believe are the ideal genes, and the possible results of it. On the "Be wary what you wish for" vein.

[Eternal_Freedom]

Thank you everyone for the discussion. Just so we are clear, this isn't the sole basis for the story. It was more of a throwawy thought that the second group declared indepedence from Earth and "practically declared themselves a new species." I was curious as to what it would take to do this.

It will become an issue later in the story, as the war becomes a total war, and some start arguing that annihilating the second group would be genocide, and hence a bad idea. (Bear in mind that the second group are trying to destroy the first group as well, so it goes both ways.)

[LaCroix]

If chihuahuas and Irish wolfhounds were wild, we might very well consider them different species- and they'd speciate further apart due to different selection pressures.

It's only because we can physically track back to the point where we started triggering artificial speciation that we think of them as being 'naturally' part of the same species.

I wouldn't exactly call a group of humans "wild", either. As humans are very successful using technology to eliminate most selection pressure, they probably won't evolve much further away from the point they are.

You might consider these kinds of dogs different species, but they aren't considered as such. Both are still dogs. The same as a pygmy is still considered human just like any other african, chinese, indian, native american or white human.
All of them are "canis", and all of them interbreed readily, if they don't kill each other instead to defend their territory. Feral dogs will act as agressively, so I don't see much difference. You could just as well call Coyotes and Wolves just a different breed of dogs, and it would work as well. They don't even look that different, and for practical reasons, Coyotes are essentially nothing but a subspecies of Wolves, just like dogs and Grey wolves. I give you the fact that coyotes do look like coyotes, and wolves like wolves. Still, dogs don't look like "DOG". There isn't a specific archetype. Just like with humans.

The question was: When will the remote group of humans definitely be a new species.
You're just saying that you can call them a new species as soon as you want to, and just need to find something they usually have in common, which the other group usually doesn't, ignoring that the variation between individuals of h. sapiens is already much bigger than the possible variation between members of h.s. terran and h.s.andromeda will be in your scenario. Size, weight, skin color, facial build, hair color and type, just about everything is highly variable in humans.

Even something like green hair wouldn't really count as much more than a freak mutation, these days. (And would probably result in research what kind of pollution caused it, and how to replicate it for fashion reasons.)

My point is that in a species with such a wide variation of individuals, the only valid way to really determine that speciation has occurred is the "nonfertile or no offspring" test.

[Mayabird]

It was more of a throwawy thought that the second group declared indepedence from Earth and "practically declared themselves a new species."

They could just be so full of themselves that they believe it despite any actual evidence to support it.
[line 2]

[Eternal_Freedom]

Now that would work very well, especially as I have the idea of them practicing eugenics as well. Them running off to Terra Nova and calling themselves Homo Sapiens Nova or somesuch would work nicely.

Incidentally, could somebody who knows Latin tell me what the correct species name woudl be, if I mean it to be "New Man?"

[Dave]

It'd be whatever you want to call it, since naming rights go to the discoverer these days. See Pheidole_harrisonfordi. You're spot on with the name already though, I think.

Warning, latin butchering ahead:
Genus Species Subspecies
Homo Sapiens Sapiens <- our subspecies
Homo Sapiens Nova <- their subspecies
Homo Sapiens Centaurus <- perhaps the Alpha Centarians

Homo Noveticus <- or a totally different species of new humanoids
Homo Vegas <- The ones from Vega
Homo Lupus <- The Wolf359-ians?

[Alyrium Denryle]

Correct answer: Until they cannot interbreed any more...

By that standard, lions and tigers are the same species.

The actual standard used these days, is that a population or organism needs to be a monophyletic lineage with a significant degree of genetic divergence from the next most closely related monophyletic lineage.

It will all depend on what the selective pressures are. If the new world is not all that different from the old one, or technological adaptation nullifies selective pressures from the environment leaving you only with genetic drift and sexual selection... give it a few hundreds of thousands of years.

H. Neanderthal is usually said to have arisen about 600,000 years ago. H. sapiens about 100,000 to 200,000 years ago. They are considered separate species, and while interbreeding may have occurred it was a rare thing, at least as far as leaving kids behind. So, no, you don't need millions of years, but you do seem to need a time span in the six digits of years.

Except that H. Sapiens did not diverge from H. Neanderthalis. Both diverged from H. Heidelbergensis. But yes, six digit years.

There's also some amateur eugenics going on, with the "unfit" being weeded out (not exterminated, just encouraged not to breed,for the good of the species.

How much of an effect might that have?

It depends on what is considered "Unfit".

As for the neanderthal/sapien thing, they're considered different species because of their different morphology. We were apparently able to interbreed with them, as (according to a fairly recent study, dumbed down here in a Scientific American article) apparently a few percent of the DNA of non-Africans comes from our H.neanderthalensis ancestors. It could be argued that we aren't separate species at all, but different subspecies of H.sapiens.

And that argument would be wrong because the Biological Species Concept is dead. If we accepted that standard, most of the world's couple thousands of species of toads would be the same species, irrespective of whether or not they diverged from the same common fucking ancestor.

The problem with modern humans is that not only are we incredible adaptable from a biological standpoint, but how powerful our technology is. The fact that we can use tools to alleviate environmental discomforts immensely reduces the impact of selective pressure.

No. It does not. It just shifts it from morphological adaptation to selection for social traits, behaviors, and cognitive processing.

God I love it when lay-people talk about evolution. It is like lapping up the years of orphaned gypsy children.

Correcting this:

Warning, latin butchering ahead:
Genus Species Subspecies
Homo sapiens sapiens <- our subspecies
Homo sapiens novus <- their subspecies (The New Homo sapiens, masculine, nominative, singular)
Homo sapiens centauri <- perhaps the Alpha Centarians (masculine,genitive)

[Eternal_Freedom]

Homo Sapiens Novus it is then. Thank you for the help everyone.

[Ziggy Stardust]

The actual standard used these days, is that a population or organism needs to be a monophyletic lineage with a significant degree of genetic divergence from the next most closely related monophyletic lineage.

And maintains this integrity across time and space, of course.

No. It does not. It just shifts it from morphological adaptation to selection for social traits, behaviors, and cognitive processing.

Alleviates was the wrong term, yes, but my point was that the type of physical speciation he wanted is not possible in a short time frame (did you see the part where he asked if 200 years was enough?). I didn't phrase it quite as clearly as I could have, but I was not trying to claim that technology eliminates selective pressure (though you can't argue it has a significant impact, especially with regards to a theoretical speciation). Also, a little earlier in that same post you said ...

"or technological adaptation nullifies selective pressures from the environment"

which was ... exactly my point!

God I love it when lay-people talk about evolution.

Sorry, love, not a lay-person. I admit that my post was a gross oversimplification, but I figured since this was for the purposes of a fan-fic by someone who admittedly does not know a lot about evolution that a lecture on neo-darwinian synthesis was unnecessary.

[Alyrium Denryle]

And maintains this integrity across time and space, of course.

Yes

"or technological adaptation nullifies selective pressures from the environment"

which was ... exactly my point!

Yeah, but you were over-expansive in the selective pressures which would be released by this. Granted, we might accidentally be equivocating here.

Take Home Message: Technology releases an organism from the selective pressures imposed by the environment outside their social context. Temperature, wind, rain, populations of non-pathogenic species, competitive interactions between species (but not other groups. Yay multi-level selection), predation etc.

What it wont release them from are selective pressures from social interactions and pathogens, which can often act to mediate selection from the environment indirectly. Even if their morphology wont adapt to harsh winters because they live inside with central heating, their culture will, and will impose strong selection on behaviors within that culture. At the end of the day, the only visible morpholgical differences will be from genetic drift, but immune systems can be completely different and cause post-zygotic hybridization barriers, pre-zygotic hybridization barriers because sexual selection and cultural evolution will reproductively isolate them from other humans. When all is said and done, there will be a sort of intergrade lineage (I assume all of these people are from different ethnic groups etc, so the stock population will not themselves descend from the same common ancestor, but that may be getting a little over-complicated), and while the phylogeny will look wierd and some parts of the topology will converge (as people with one set of mitochondrial and Y chromosome haplotypes interbreed), a new species will be formed.

Sorry, love, not a lay-person

My apologies. Though the comment was not specific to you.

a lecture on neo-darwinian synthesis was unnecessary.

It is ALWAYS necessary.

[Esquire]

If chihuahuas and Irish wolfhounds were wild, we might very well consider them different species- and they'd speciate further apart due to different selection pressures.

It's only because we can physically track back to the point where we started triggering artificial speciation that we think of them as being 'naturally' part of the same species.

While I hate to throw in something as insubstantial as hearsay, I've heard from multiple people that most of the various kinds of dog will, if left free from artificial influences and left to mix with each other, turn into a medium-sized brown dingo-like creature within a few generations. That seems to be another reason for considering dogs one species, if it's actually true.

[Ziggy Stardust]

Yeah, but you were over-expansive in the selective pressures which would be released by this.

Fair enough.

Take Home Message: Technology releases an organism from the selective pressures imposed by the environment outside their social context. Temperature, wind, rain, populations of non-pathogenic species, competitive interactions between species (but not other groups. Yay multi-level selection), predation etc.

But radiation still causes freak mutations that lead to superpowers, right? That's ... that's science ...

(as people with one set of mitochondrial and Y chromosome haplotypes interbreed)

Ooh, I didn't even think about that. Actually gives me some ideas for my own potential sci fi ...

Sorry, love, not a lay-person

No worries. It's not like my post exactly broadcasted a high degree of scientific competence.

It is ALWAYS necessary.

Conceded.

[Alyrium Denryle]

But radiation still causes freak mutations that lead to superpowers, right? That's ... that's science ...

Only if you consider cancer to be a superpower

"Oh no! OncoMan is here! RUN BEFORE HE REACHES THE LYMPHATIC SYSTEM AND SPREADS TO THE ORGANS!"