So, how do people explain the Rhesus negative blood type?
It’s a real evolutionary disadvantage, it causes miscarriages and infant deaths . Some notable biologists, including Haldane, have pointed out that it should have been selected out by now. In fact, it should have been selected out in the first few generations, to reside at the background level it has in Africa and the far East. But western Europeans carry it at a very high rate, Basques at about 40%.
There’s only two ways this could work. That the Rhesus positive blood type is a relatively recent mutation, probably from the horn of Africa, that has swept across a pre existing, global population of humans and replacing them. Or that there was a massive input of Rhesus negative blood types relatively recently, and mainly occurring in central Europe, and we are actively in the process of selecting it out.
The second idea supports my Neanderthal theory. It also fits with the increasing occurrence of occipital buns as you go back into the iron and bronze age. If you could work out some kind of convergence date for the two… has any body tried DNA testing iron age humans to see if they have a higher incidence of RH-? It would give a good way to work out how fast it is decreasing, and from that, when the trait entered our gene pool. It might be a good idea to do DNA analyses for all kinds of traits, to see if they are more common or less, and if they can work out a point/time of entry into the modern Sapiens gene pool.
The Rh+ ‘killing’ off the Rh- might explain the limitation in the human gene pool to some extent, and why some minority mitochondrial DNA lines might have died out. This could seriously put the ‘out of Africa’ migration back in time, not that the 60kya number could be right anyway. Introducing Rh+ would make a population have breeding difficulties until it became dominant. Maybe it’s the reason the number of Neanderthals slowly reduced.
Logically, Rh- would have to been the standard blood type of homo erectus and earliest humans, with Rh+ slowly asserting dominance as Rh- women failed to reproduce as well as their Rh+ sisters.
I think malaria may have been another significant factor in human evolution. There is blood factor called the ‘Duffy antigen’. If you are Duffy negative, you have a slight resistance to Malaria, and you are African. Since all Europeans are Duffy positive, this gene must have spread after malaria evolved, and after the migration out of Africa . Other genes that cause resistance to malaria, like sickle cell and Thalassaemia, are generally fairly localised, but Duffy negative blood is common to nearly all Africans. The first appearance of Malaria must have been after farming developed, and it probably erased nearly all the first farming civilisations, and killed off whole populations across the tropical zone. Only hunter gatherers with very low population densities could have survived this, like the Khoisan and the Pygmies. Anyone in a more densely populated area would have become infected, and very few children would have survived.