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So a hybrid is not a species? So, that would mean some creatures are not species at all?
Nope, just hybrids. Although, they are of purely mammalian decent, and are quadrupeds.OK, but do they come under some other more general umbrella then? I don't know, 'quadruped mammals' or something.
OK, but do they come under some other more general umbrella then? I don't know, 'quadruped mammals' or something.
No, I had no expectations for the quality of the questions. Some people really don't know that much about biology or evolution, others know a bit, and their questions will reflect their knowledge accurately as long as they aren't asking them to be snide. I'd rather you not insult the questions or those asking them. Curiosity is a good thing, and I don't want people to be deterred from asking questions by making them face condescension.
There is a species in which this situation has occurred: the desert grassland whiptail lizard. All members of this species are females that give birth to young without fertilization necessary. Humorously, they do need to imitate sexual intercourse with another member of their species to instigate it, so, a bunch of lesbian lizards. Their offspring are all clones of themselves. They don't have both male and female genitalia, however, but rather their ova have complete genomes (diploid) rather than the half genomes (haploid) typical of species with both male and female sex cells. A correction, after looking them up, this is a triploid species (which means they have triplets of chromosomes), so this means that their offspring are not perfect clones of themselves genetically, as they could potentially not inherit the same exact chromosome set due to there being duplication after meiosis to make the ova have a complete amount of chromosomes. Fascinating.Ok, that seems to make some sort of sense. Thanks
However, on a human level, say, going by your above explanation, (I realise this isn't exactly the same sort of thing), but what would happen if, for example, there were gradually fewer and fewer men or fewer and fewer women? Do you think that one or the other genders might evolve so that, for example, some men would start, oh I don't know, growing female sexual reproductive organs, so that they could carry on having offspring? Or maybe, even, they could develop within themselves both sperm and ova which somehow could fertilise themselves and (the man would presumably have to have some kind of womb) and each individual could produce and give birth to a baby. And if this were to happen, would those humans actually be a different spoecies then?
Sorry I'm probably not phrasing the question very well, but I'm not up on correct terminology and am trying to get my head around how these sorts of things work.
T
We have so many fossils of hominids throughout the ages, and we sometimes find it hard to distinguish the difference between them at the base of their divergences or axis of change. Their fossils though tell us enough that we know they're different enough to be separate species for the purposes of classification.
Other barriers to reproduction also are taken into consideration. For example, the vast majority of the modern human population does NOT have Neanderthal DNA (and, for those that do, it's such a small portion as to be negligible, I once mathematically showed it to be something between 5-25 of the more than 20,000 genes humans have at most, and we share many of the same genes with Neanderthals since they are a closely related species to us, so that's the max difference it would make).If all these different hominids were living together, would they be able to produce children? If so, would some of the children be hybrid (therefore likely to be infertile). I ask this because you are saying that they are regarded as different species. But if they were able to reproduce amongst themselves interchangeably, then surely that would count them as one species? (I know that probably didn't happen in actuality, but I'm just saying, IF they'd all somehow got together).
They know now, for example that 'modern' humans and Neanderthal interbred, and very, very many of present day humans have Neanderthal DNA in them.
If all these different hominids were living together, would they be able to produce children? If so, would some of the children be hybrid (therefore likely to be infertile). I ask this because you are saying that they are regarded as different species. But if they were able to reproduce amongst themselves interchangeably, then surely that would count them as one species? (I know that probably didn't happen in actuality, but I'm just saying, IF they'd all somehow got together).
They know now, for example that 'modern' humans and Neanderthal interbred, and very, very many of present day humans have Neanderthal DNA in them.
Other barriers to reproduction also are taken into consideration. For example, the vast majority of the modern human population does NOT have Neanderthal DNA (and, for those that do, it's such a small portion as to be negligible, I once mathematically showed it to be something between 5-25 of the more than 20,000 genes humans have at most, and we share many of the same genes with Neanderthals since they are a closely related species to us, so that's the max difference it would make).
Basically, the cross-breeding between Neanderthals and our species was never significant enough, and the genetic differences too significant, to consider us the same species. We don't even have the same area of origin; while Homo sapiens migrated from Africa to the rest of the world, Neanderthals are natives of Europe.
Pygmies are still human, just naturally very short without any of the dwarfisms, so they could have children with any other human. As it were, they happen to be dying out.Thanks. But what other barriers to reproduction are taken into consideration? I can see, for example, it probably wouldn't be a good thing for a female chihuaha to mate with a great dane...the chichuaha would no doubt die, if not from giving birth to a probably huge puppy, but probably from the sexual act itself. But if these various homo species were more or less the same size, especially pelvically for a female, what other problems would there be? I assume that modern day pygmies and a masai could have children? Or maybe not?
Pygmies are still human, just naturally very short without any of the dwarfisms, so they could have children with any other human. As it were, they happen to be dying out.
Other barriers to reproduction include geographic barriers (two species could mate and produce fertile offspring, but they don't have populations that come into contact with each other, so they don't), mating season differences and differences in courtship (prevents many bird species from interbreeding; they get pretty picky about mating dances), as well as others. While humans aren't known to be particularly picky, not many would have gone to make babies with a Homo erectus even if it were biologically possible http://www.museon.nl/sites/default/files/styles/detailpage_main_image/public/import/Dig092-06-018_Homo Erectus_0.jpg?itok=p2gebW7S
Don't forget that you are also a member of a highly territorial, naturally xenophobic species. If we can't even get along with members of our own species most of the time, what makes you think we'd get all friendly with a different species of the same genus? We're part of the reason that we're the only species in our genus alive today.
Pygmies are still human, just naturally very short without any of the dwarfisms, so they could have children with any other human. As it were, they happen to be dying out.
Other barriers to reproduction include geographic barriers (two species could mate and produce fertile offspring, but they don't have populations that come into contact with each other, so they don't), mating season differences and differences in courtship (prevents many bird species from interbreeding; they get pretty picky about mating dances), as well as others. While humans aren't known to be particularly picky, not many would have gone to make babies with a Homo erectus even if it were biologically possible http://www.museon.nl/sites/default/files/styles/detailpage_main_image/public/import/Dig092-06-018_Homo Erectus_0.jpg?itok=p2gebW7S
Don't forget that you are also a member of a highly territorial, naturally xenophobic species. If we can't even get along with members of our own species most of the time, what makes you think we'd get all friendly with a different species of the same genus? We're part of the reason that we're the only species in our genus alive today.
In all likelihood, Yes. Depends though on how long they'd have been genetically isolated from each other.If all these different hominids were living together, would they be able to produce children?
All depends on how far past their separation they were before coming back to reproduce, but yes, it could've been possible. If they did, and did it enough then their dna would recombine to essentially merge traits to again become the same species. This coming together could happen here and there in small pockets, but then this would still lead to diverging populations, eventually leading to the differences that still lead to speciation if it wasn't regular, such as tigers/lions or horses/donkeys where offspring are largely infertile. At this point, the two divergent populations are all but guaranteed to be forever separate. All this is moot though if the two genetically capable groups choose not to interbreed then the effect will still be the same. This is how we could've become had we not overcome our racism as a species today. The various (and clearly identifiable) human races we already have would've continued to speciate, eventually becoming genetically unique and forever divergent.If so, would some of the children be hybrid (therefore likely to be infertile). I ask this because you are saying that they are regarded as different species. But if they were able to reproduce amongst themselves interchangeably, then surely that would count them as one species? (I know that probably didn't happen in actuality, but I'm just saying, IF they'd all somehow got together).
Exactly! But to highlight your (likely correct) posit that it happened rarely, up until say 50-100 years ago, the human race we are today was largely ....well, racist. We even had laws against interracial marriages in pretty much every civilised nation, and those that did buck the trend were outcast with great fervor, often by both racial groups. Every human race in existence today is borne out of a separation of reproductive populations from a largely intact population from some 40,000 - 160,000 years ago (going by mitochondrial dna profiles today), depending on how we divide them. On that info, imagine how racist (...or species-ist?) divergent groups of hominids would be with each other? I'd even go so far as to say that the neanderthal dna we do have today may not even have been via consensual acts, in the same way the old testament described how the hebrews were rewarded for the conquering of other tribes, by keeping their virgin girls for example.They know now, for example that 'modern' humans and Neanderthal interbred, and very, very many of present day humans have Neanderthal DNA in them.
Sickle cell anemia is a special case. While in the modern day it is a disadvantage, in pre technological areas prone to maleria it is a huge advantage to be a carrier of the trait. (It would still suck to have full blown sickle cell anemia though).Well, yes I realised that there would have been geographical boundaries etc.(I also know pygmies are human!!!). But if different species of humans had somehow been intermingling, perhaps they wouldn't have been too bothered about some of the differences in looks.
No, I really wondered if there would have been any biological or physical difficulties in their interbreeding, in which case, we modern humans might have looked somewhat different with all the various genes or DNA or whatever. Also, perhaps some early humans might have been more prone to different physical weaknesses or diseases than others? Would interbreeding have protected against that ultimately? For example, I believe that, is it African people, are more prone to getting, is it sickle cell anaemia or something? Sorry, hazy on that, but I hope you get my drift. If, say, all Africans and all Chinese and all Europeans were now to be having children together all the time (forget about geographical, cultural or whatever barriers) would that be more likely to eradicate some of those things which certain populations may be prone to?
Sickle cell anemia is a special case. While in the modern day it is a disadvantage, in pre technological areas prone to maleria it is a huge advantage to be a carrier of the trait. (It would still suck to have full blown sickle cell anemia though).
Also, despite the higher instances of Neanderthal DNA in Europeans, Africans have more genetic diversity then the rest of the human population put together.
I once read an idea (can't find any confirmation) that white skin adaption to the dark European winters might be a Neanderthal trait. But it's just as likely that general pressure favored being pale independently in both humans and Neanderthals.
Good questions.But I do have a question. I realise that people who live in very sunny countries like Africa or India would have dark skin, and that it would be advantageous for inhabitants of Britain, Scandinavia etc to have pale skin (if only to absorb the maximum amount of Vitamin D from the sun). But I'm not sure how gradually the people would change so that inherently they would be be born with dark or light skin. I realise that there is gradual change, but does that mean that the first people migrating from Africa would have been dying off in hordes because they couldn't survive in other climes..and vice-versa?
Do you think that present-day Africans, living in Britain,say, who kept marrying other black people (not white people) that their progeny would eventually also become more and more pale-skinned because of our relative lack of sunlight, and if so, how long that might take? (I do understand that we all have various levels of pigmentation and that both dark and light skinned people will get darker or lighter according to our exposure to the sun..but that is only temporary). What I mean is, how do the genetics change?
Good questions.
The genetics will change in two ways:
1. Those genes already in the population that lead to lighter skin will be favoured over those that lead to darker skin.
The advantage need only be very small, but acting over generations it will lead to a move to lighter skin.
For this reason the migrants would not have been "dying in hordes", but those with the darkest skins would have been at a disadvantage and would have tended to be less successful in the reproduction game.
2. Mutations of the genes responsible for pigmentation and that would lead to lighter skin would continue to occur as, just as they had in Africa. However, in Africa those mutations would be disadvantageous and would, therefore, tend to die out over time.
Would sub-Saharan Africans develop light skins over generations if they remained living in northern climes? Yes and no.
Yes, if they lived an existence comparable with our mutual ancestors. No, if they chose to take the vitamin supplements that overcame the limitations of a dark skin in light deficient environment.
As to timing, I would think a few hundred generations might be sufficient. There is research on this: if I can locate a reference quickly I shall post it later
Supplements are generally ineffective as a means of getting the vitamin D one needs, and it is difficult to get it through one's diet as well. This is why vitamin D has been put into milk. The symptoms of a severe vitamin D deficiency are pain in the bones and general weakness of the body, as well as more frequent infections. However, it is not uncommon for people with mild to even moderate deficiencies not to notice any or have very mild symptoms. The risk of this deficiency is far greater for pregnant women, as it will deplete more with the pregnancy, and make their breast milk have less vitamin D, thus making their children have the deficiency and have an increased risk of infection and death.But why would darker skinned people be at a disadvantage when it comes to reproduction? I mean, surely they could reproduce, but perhaps their chldren would be less able to survive for so long?
Also, do present-day Africans living in the west (countries such as Britain or ones where there is a lot less sun) take vitamin supplements generally speaking?
Well, due to how the expression of skin tone genes works (incomplete dominance, most to all genes related to skin color are expressed equally, resulting in an intermediate trait), it would be highly irregular to the point of paternity being questionable for two very pale skinned people to have a baby that is very dark skinned. Not saying it isn't possible, but it's unusual. However, it is not uncommon for people with medium to dark skin to have some interesting children; these two cuties happen to be twins https://s-media-cache-ak0.pinimg.com/736x/8c/70/2d/8c702dd6451b1a4677f6e63c9a06b97b.jpgObviously when a black person marries a white person, then their children tend to have paler skin. However, I have read that occasionally someone has given birth to a black person totally unexpectedly, as there was some (perhaps unbeknownst to them) black ancestry in their family.
Well, yes I realised that there would have been geographical boundaries etc.(I also know pygmies are human!!!). But if different species of humans had somehow been intermingling, perhaps they wouldn't have been too bothered about some of the differences in looks.
Well, due to how the expression of skin tone genes works (incomplete dominance, most to all genes related to skin color are expressed equally, resulting in an intermediate trait), it would be highly irregular to the point of paternity being questionable for two very pale skinned people to have a baby that is very dark skinned. Not saying it isn't possible, but it's unusual. However, it is not uncommon for people with medium to dark skin to have some interesting children; these two cuties happen to be twins https://s-media-cache-ak0.pinimg.com/736x/8c/70/2d/8c702dd6451b1a4677f6e63c9a06b97b.jpg
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