human speciation

[CPL.Luke]

if the europeans hadn't moved all over the world and started a regular genetic trade between different regions all over the world, how long would it have taken for homo sapiens to split into 2 or more species?

[Ophiolite]

It wasn't just the Europeans. Genetic studies show we have been a remarkably well travelled species. There are more genetic differences within the current 'races' than there are between them. Since we have not been geographically isolated anywhere for any length of time the prospect of speciation was always small. We'll likely have to wait for interstellar travel before the necessary conditions are met.

[LucidDreamer]

Never. One of the other populations of man would have spread all over the world if the Europeans didn't.

 

I am assuming that you mean that there is something preventing humans from spreading all over the world and that something keeps them isolated. The problem is that there is no definitive means to separate two populations into two different species. There is also no standard rate of evolution that we could use to estimate how long it might take to reach a certain level of difference. That means that any type of calculation would be at best a farfetched speculation.

 

So my answer is: 197,000.7654321 years

 

Seriously though, since it took a hundred thousand years to several hundred thousand years to separate Homo erectus from Homo sapiens, and given approximately the same amount of natural selection, I would say about the same amount of time to create two different species of man. But in a different situation with smaller more isolated populations and more selective pressures it could be conceivably done in a shorter period of time, probably less than 100,000 years.

[Martin]

if the europeans hadn't moved all over the world and started a regular genetic trade between different regions all over the world, how long would it have taken for homo sapiens to split into 2 or more species?

 

 

rats, when I saw your thread title "human speciation" I thought, hey! that might be a good idea! this Luke is maybe proposing we try speciating---like maybe some sub-population voluntarily wants to try splitting off.

 

maybe there are two types A and B and the B people look indistinguishable they just can have sex with A people without anybody getting pregnant.

 

Like all the Maori, or all the Navajos, decide they want to be a separate species and make it impossible to have a fertile union between a Maori and somebody else. They take a risk of extinction here but maybe they want to preserve this identity so they all do whatever genetic engineering thing is necessary. After that, the Maori gene pool cant mix with the other Big gene pool.

 

Of course they can have sex with any non-Maori they want, that wants to. but it ordinarily wouldn't work to get married if they wanted to have children in the usual way.

 

lots of human groups tend to marry among themselves, but a human SPECIES would be such a group that took the step of making it permanent, say by doubling or rearranging some piece of some chromosome or whatnot. Technically I dont know how it would be done.

 

something to think about. maybe some day some group would want to try it and a new species would be made.

[ydoaPs]

Technically I dont know how it would be done.

 

something to think about. maybe some day some group would want to try it and a new species would be made.

physical isolation. they could make a colony on the moon or something. eventually, given no procreation with the other group, humans would be two different species.

[CPL.Luke]

I know that it takes about 10,000 years for a population of people with black skin to become a population of people with white skin (provided they are far enough north) and visa versa.

 

so there must be some amount of time less than 100,000 years for humans to become multiple species.

[zyncod]

It would take quite a long time to actually form two separate species, depending on the definition. If you're looking for the inability of two groups of humans to produce fertile offspring, that would take millions of years. If you're looking for simple reproductive isolation, the Maoris and Navajos are essentially two separate species because they don't reproduce (geographic isolation). If the Maori and Navajo were the only two groups of humans on Earth, scientists would likely consider them separate species.

[Martin]

... making it permanent' date=' say by doubling or rearranging some piece of some chromosome or whatnot. Technically I dont know how it would be done.

...[/quote']

 

nobody has yet indicated they understand what I am talking about so I will try to say it better

 

I am not talking about isolation, like putting one group on an island or the moon

 

I am not talking about relying on chance mutations in subpopulations geographically separate----or about isolation by custom or religion or cultural preference etc.

 

I am talking about SOMETHING THAT IS SOMETIMES DONE IN THE LAB WITH OTHER SPECIES where you ENGINEER a genetic change that is like doubling a chromosome or something more subtle than that and gets you a new population where there is enough chromosomal incompatibility that matings between groups simply cannot be fertile. I don't know how this could be done, but nowadays there are a lot of genetic engineering techniques and I suspect that it could be done.

 

You could argue that it would be highly undesirable to do it. that's OK if you want to argue that. I want the possibility to be clear though.

[ecoli]

It depends on the environmental pressures that would exist if a certain groups of humans were isolated. If there are no favorable mutations, then the species would not evolve, right? If we go to the moon, and set up a colony to mimic conditions on earth, why would any genetic variation (on the scale required to creating a new species) occur?

[ydoaPs]

It depends on the environmental pressures that would exist if a certain groups of humans were isolated. If there are no favorable mutations, then the species would not evolve, right? If we go to the moon, and set up a colony to mimic conditions on earth, why would any genetic variation (on the scale required to creating a new species) occur?

for start, less gravity. different nutrients in the soil(unless you bring some from earth).......

[Hellbender]

even if the conditions were made the same or similar, founder effect and random drift can still occur. These may not always be as drastic as natural selection, but it is still evolution.

[ecoli]

Obviously...but enough so that a different species would arise? I'm not so sure.

[Hellbender]

Obviously...but enough so that a different species would arise? I'm not so sure.

given enough time..possibly.

[Mokele]

Genetic drift can cause differentiation of body parts, with the best example being bat penises. See, bats are ungodly hard to classify, since just about everything about them is modified for flight and cannot change much. But their naughty bits are free to change, and indeed we see a diverse array of bat willies. Since there seem to be no repeated themes in bat willies, nor any great degree of difference, they might simply be different due to genetic drift. If so, it's possible that genetic drift could alter the endowment of males (and the corresponding parts of females) such that they don't fit with the members of the other species.

 

The same could also be true for breeding colors, calls, displays, dances, etc. I just thought bat willies would be the most fun to talk about.

 

Mokele

[zyncod]

Genetic drift and the founder effect are actually the primary mechanisms of speciation. Given two very similar populations, natural selection will tend to act on them in the same way. Given enough time (and enough drift), natural selection will act very differently on the two populations, leading to speciation.

[Mokele]

Given two very similar populations, natural selection will tend to act on them in the same way.

 

Only if the environment is the same. If it's not, then natural selection can become the prime agent for increasing differences, or at least a big factor. In some cases, it can also alter breeding behavior or mechanisms enough to cause reproductive isolation, if the differences in environment require differences in breeding (amphibians would be prone to this sort of speciation, for example).

 

Mokele

[Martin]

... If so' date=' it's possible that genetic drift could alter the endowment of males (and the corresponding parts of females) such that they don't fit with the members of the other species.

 

The same could also be true for breeding colors, calls, displays, dances, etc. I just thought bat willies would be the most fun to talk about.

...[/quote']

 

Mokele, if not too much trouble I'd appreciate some help imagining the detail of a small intentional rapid speciation project. I dont know sufficient genetic technology or bio basics to supply the detail myself.

 

suppose some group, like Basques or Maori or Welsh, decided they would create a species that WOULDN'T LOOK ANY DIFFERENT from people in the surrounding population but which would be genetically isolated.

 

(forget about why, I cant imagine why they would want to, but assume they have some compelling reason and have decided)

 

So suppose what happens is that each Welsh couple says they will have ONE in vitro fertilized offspring----so around the time of in vitro procedure some specified genetic manipulation can be done---some rearrangement of chromosomes or whatever---call it "Procedure Z". And the same couple can decide to have other children too where they dont necessarily bother with the in vitro rigamarole.

 

So each Welsh couple goes and has one in vitro speciated child that looks just like their other kids but a population of several million is created which can not interbreed with the main population.

 

My question is what could this "Procedure Z" be? It has to be harmless or neutral in phenotypic effect, and yet it still has to result in a set of chromosomes that is incompatible with mainpopulation human chromosomes.

 

How many sites would have to be involved? Is there any way that "junk" could be used? Is major structural change on one or more chromosomes necessary (even desirable) or could maybe tampering with just ONE wellchosen GENE do the trick?

[Mokele]

Unfortunately, I don't know, and I'm not sure if anyone else really knows either. So far as I know, the mechanisms for speciation (evolutionary and genetic) are a hot and very contentious topic at the moment. Numerous mechanisms can produce speciation, such as genetic drift, sexual selection, natural selection, etc, but all rely on differing environments (habitat or microhabitat) to produce phenotypic change. Causing speciation without phenotypic change and with sympatic group is a tall order, even if we'd be doing it artificially.

 

To the best of my knowledge, the only such cases are in plants via polyploidy. Essentially, plants often produce gametes with the full diploid number of chromosomes. If those gametes meet a conspecific haploid gamete, you get a sterile plant (since the chromosomes cannot segregate properly), which is where seedless plants come from. If two erroneously-produced diploid gametes meet, you get a plant that's basically the same (often bigger and stronger) but cannot reproduce with the main population because it'd produce gamtes with the diploid set, which would meet haploid ones from the main population. We've seen speciation via polyploidy in plants a *lot*, but I'm unsure about animals. I've heard a few things regarding some unusual salamanders and lizards, but nothing's certain yet, and those individuals are actually noted for being asexual, capable of reproducing without males (some of them even are all-female species). As for what'd happen to a mammal, who knows? Trisomy 21 produces Down's syndrome, so clearly we can't just add chromosomes all over, but there might still be a way.

 

So basically, if this is for a sci-fi novel or game or somesuch, just make something up, because it'll probably be decades before we can actually give a potential method with any certainty.

 

Mokele

[LucidDreamer]

Mokele' date=' if not too much trouble I'd appreciate some help imagining the detail of a small intentional rapid speciation project. I dont know sufficient genetic technology or bio basics to supply the detail myself.

 

suppose some group, like Basques or Maori or Welsh, decided they would create a species that WOULDN'T LOOK ANY DIFFERENT from people in the surrounding population but which would be genetically isolated.

 

(forget about why, I cant imagine why they would want to, but assume they have some compelling reason and have decided)

 

So suppose what happens is that each Welsh couple says they will have ONE in vitro fertilized offspring----so around the time of in vitro procedure some specified genetic manipulation can be done---some rearrangement of chromosomes or whatever---call it "Procedure Z". And the same couple can decide to have other children too where they dont necessarily bother with the in vitro rigamarole.

 

So each Welsh couple goes and has one in vitro speciated child that looks just like their other kids but a population of several million is created which can not interbreed with the main population.

 

My question is what could this "Procedure Z" be? It has to be harmless or neutral in phenotypic effect, and yet it still has to result in a set of chromosomes that is incompatible with mainpopulation human chromosomes.

 

How many sites would have to be involved? Is there any way that "junk" could be used? Is major structural change on one or more chromosomes necessary (even desirable) or could maybe tampering with just ONE wellchosen GENE do the trick?[/quote']

Forgive me for butting in, but I believe I know a way you could create your "procedure Z". There are numerous diseases that are caused by problems with chromosomal replication, division, and separation during the formation of gamete cells. Various problems can occur, which result in various outcomes with different degrees of disorder or fatality for the offspring that results.

 

There are diseases that are caused by pieces of one chromosome breaking off, often at specific fragile sites on the chromosome. Let's call the normal chromosome for this example chromosome z, the fragile site will be called fragile site z, the piece that breaks off will be called piece Z alpha, and the remaining fragment of the chromosome z without the missing piece will be called piece Z beta. Together Z alpha and Z beta make a full Z chromosome.

 

Sometimes the broken piece, Z alpha, stays separated from the rest of the chromosomes and when separation occurs it can be included in one of the gametes formed. If the broken piece is included in the gamete that already has the full Z chromosome then the offspring that results is likely to have a disorder caused by the extra duplicate genetic material from Z alpha. This is just what causes one form of Down syndrome where an extra portion of chromosome 21 is included in the gamete. The other gamete that is formed is missing the genes coded by the z alpha section and there will probably be so many problems that no offspring will result from this gamete.

 

Sometimes during separation the broken piece, Z alpha, will be moved to the same gamete that has the Z beta section and together they make a full Z chromosome. Sometimes the broken piece will attach to another chromosome, let’s call it y, and make a larger chromosome, so the genome that results will have a completely normal amount of the normal genes, but one his chromosomes will be smaller than normal, Z, and one of the chromosomes will be larger than normal, y. The offspring that results from this gamete might be completely normal, (depending on the affects of gene activation resulting from chromosomal affects on expression-but ignore this for this discussion).

 

So although this person might look totally normal, they will have a strong chance of having a child with a disorder because they might pass down either the small Z chromosome (beta Z) or the large y chromosome with the extra genetic material (alpha Z). They may also have normal children if they luck out and pass down the chromosomes from the parent that did not give them the abnormal chromosomes.

 

So in order to create a population that is totally phenotypic ally normal, but can not breed with the rest of the population all you have to do is mate people with the same abnormal chromosomes. You would need to use some sort of selection process, in vitro or in vivo, to weed out the normal chromosomes to end up with a population that has the new "abnormal" z and y chromosomes. It would not be difficult to find two people with the same abnormal chromosomes, because like I said there are common fragile sites and these pieces will often attach to another specific chromosome. Also, you would choose the abnormal chromosomes so that the population could not successfully mate with the normal population.