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.
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).
. 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.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
In all likelihood, Yes. Depends though on how long they'd have been genetically isolated from each other.
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.
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.
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).
Good questions.
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.
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
. You'd never guess, would you? Especially if those are the parents, you wouldn't think that the one child would be so very fair (unless perhaps one of the grandparents was lighter-skinned).
