What is the evolutionary advantage to humans having multiple blood types ?

Previous question. Is blood type linked to personality?

There is no evolutionary “advantage”. It just happened that way.

Quite the opposite, a good number of infant deaths are due babies with rhesus positive type and the mother has negative or the other way around. I would call that a disadvantage.

The premise in incorrect. It assumes that all human genotypes represent an evolutionary advantage.

But it’s still a GQ so here you go.

I don’t think there is any advantage. I’ve never heard of any scientific proof that a particular blood type helps guard against things that might be harmful. I remember information on sickle cell helping guard against malaria, or maybe people with sickle cell also have the genes that guard against malaria, I am not sure exactly how that works, but blood type? I think the different blood types just create problems more than anything else.

The babies which die are after a first has been born. If the mother is rh negative, and has a baby which is rh positive, she needs a shot. Otherwise, if the infant spills any blood during birth, mother’s blood can develop antibodies. Those antibodies are a threat to any future rh positive baby. It can mean blindness, disfigurement, or death. So long as this is known, it is easily prevented.
The most frequent occurrence is with miscarriage or abortion.

There is no real advantage to having more than one blood type, except differences help to prevent single branch genealogy.

@Patty_Melt What is single branch genealogy?

Like when siblings mate.

@Patty_Melt What does blood type have to do with that? There isn’t any problems with people being homozygous for blood type.

It doesn’t directly. But it factors in with the other DNA differences.

“Having blood types” is a medical frame of reference. The ABO+/- systems is code for the presence or absence of three particular common antigens on our blood cells. They’re important because of the way our immune systems work. There are all sorts of other antigens that our immune system can respond to, to protect us from infections.

I suppose in theory every human could evolve to have the same sets of blood antigens so we could all transfuse blood. ... In order for that to happen though, we’d pretty much need to hook ourselves all up to a giant infusion system, and/or just massacre every human who doesn’t have AB+ blood type. That’s how evolution works.

The advantage in not slaughtering every human without AB+ blood type, is in all the other qualities of those people other than their blood types and the inconvenience of having to organize blood banks.

I don’t know about you, but I figure it’s probably a favorable trade off, to let them live..

On the other hand, reducing the human population could help slow down our industries’ devastation of our planet… but the wars that would break out, out of trying to organize mass slaughter based on blood type, would probably involve even more damage. So let’s not suggest it.

AB blood group reduces the severity of cholera.
O blood type reduces the severity of malaria.

@Zaku It wouldn’t work. AB parents could still have children who are just A or just B. I think you also can wind up with RH negative. I assume negative is a recessive trait, but RH I don’t remember well if we can be positive and negative from each parent, and so then we are positive. You can’t “fix it” with mass slaughter by choosing AB to survive. it would have to be ongoing killings forever. You would have effectively gotten rid of 0 blood type though if you choose AB individuals only to live in your scenario.

If you went with just saving the 0 negative people then you might be able to do it, but that’s not a lot of people. Eventuality, it could take thousands of years, you might get a new mutation.

@Patty_Melt Do you mean the gene sequence close to blood type on the DNA strand? That they tend to move together? That is something that is studied to explain why red headed people might be more resistant to anesthetics for instance.

@Lightlyseared I hadn’t heard that. I googled a little and the cholera statement, all I could find was an extremely small study. I don’t give it any credence if that’s all there is, but maybe there have been larger studies. What I read about malaria they cited type O being predominant in areas with high malaria risk. That wouldn’t necessarily prove anything either. But, it is interesting if the blood types do have some sort of protection.

I found this link with blood type distribution by country. Very interesting. https://en.m.wikipedia.org/wiki/Blood_type_distribution_by_country

@Zaku to clarify, because I don’t think I was clear.

AB parents can have A, B, or AB children.

Rh positive parents can have positive or negative children.

0 parents can only have 0 babies.

Rh negative parents can only have negative babies.

In addition to protection from certain diseases associated with a specific blood type, there is a general evolutionary advantage to having multiple blood types. It makes it more difficult for pathogens to fine tune their adaptive behavior.

Shooting from the hip EVERYTHING about any life form is an evolutionary question mark defined by (in our case) 10’s of thousands of years of evolutionary trial and error. Things like blood type, appendix’s, hair color, eye color, height, weight, blood type and most importantly our immune systems are the current results and artifacts of our evolutionary journey. Blood born pathogens are among our greatest threat to a species survival and multiple blood types give the best odds for survival of us humans. So in theory a pathogen/virus might find success on attacking one blood type where at least (in theory) one blood type will demonstrate an ability to remain unscathed by a novel pathogen virus and survive an otherwise species extinction event. Who knows humans may have at one time had 20 different blood types and our 5 have proven to be the most successful types and sub types in our evolutionary journey to date.

Well, you’ll just have to keep killing all the non AB+ children until you achieve blood type purity, if that’s what you want to “evolve”.

Of course I’m being facetious, in an effort someone understands that “evolving” to not have blood types would involve something killing off everyone who carries the genes to result in them.

That’s how evolution and natural selection generally work.