Kinds of Blood

[npoe1]

Well, I do not know if this question should be here but I know that I want the from the guys of this category, so, What is the advantage (evolutive) that give to have different kind of blood in humans?, Why some people have A rh +, B rh -?, Is some type of blood better to something than the others?, I hope that a few of you know the answer.

 

[Missing Ghost]

I think it's to protect against external bodies entering in the blood. ex: if external blood enters it coagulates. However, like many things created by nature it may just be useless.
BTW, nice to know some vampires like PC hardware.

 

[TraumaRN]

While I'm exhausted so my answer might be wrong but if I recall it's essentially a way for your body to determine 'self' from 'non-self' in term of Rh + protein marker vs Rh -

I'm trying to remember so someone else might have to elaborate but one of the types of WBCs goes around the body 'testing' itself on various cells and if they have the right marker, such as Rh + then it recognizes 'self' and does nothing. However if it discovers an Rh- cell then it will set off the body's immune/inflammatory response.

If no one has answered by morning I'll get my book and elaborate more.

 

[Mark R]

There isn't a very clear reason for the existance of most of the different blood groups - they may be an evolutionary remnant from a time when they were useful.

However, some do still have an advantage - e.g. Duffy- blood group offers a little protection against malaria, compared to Duffy+ (so it's quite common in Asia and Africa). Though if the advantage was particularly great, why is there Duffy+ at all? You'd have thought it would have died out.

There may be some very subtle differences in the health-profile of the different groups - with each providing beneficial and detrimental effects in some way. There's a little evidence that Group O people are more sensitive to Cholera than other groups (one possible reason why group O is slightly less common in Tropical areas).

 

[Gibsons]

I don't think there's really that much of a reason for various blood group antigens. In the current world, they're perhaps best thought of neutral mutations, neither selected for nor against in most cases.

On the other hand, (at the risk of repeating what Mark R said) you can probably find some situations where one blood group is advantageous (or disadvantageous), but the examples of that seem to be pretty limited, at least in the 21st century. Maybe one day a pathogen will show up that really gives and advantage to one group or the other, but don't hold your breath.

 

[Witling]

Genetic changes can be nuetral, neither harmful nor advantageous. We existed for a long, long time as fairly isolated small bands who just got together occasionally, It may have developed there. Second, sometimes changes manifest themselves in more than one way, e.g., (theoretical) in a fish there may be a modification of a protien that catalyzes reactions better than the original protein in a different temperature range, but incidentally, this also gives the fish's tail a red color. It's not the tail color that's the important part of the change.

 

[TraumaRN]

OP I have a very long and technical article concerning blood typings, antigens, phenotypes etc, it's much too long to post here IMO unless people want me to, if you think want the article just PM me with an e-mail addy and I'll send it.

However the articles doesnt speak to why humans are this way but it does show some differences in blood typing/phenotypes etc across ethnic groups

 

[BrownTown]

i've heard of some advantages to differnet blood types, but ntohing major. Mostly its just a completely neutral thing. You could just as easily as why do some people have brown eyes or blue eyes. Or attached earlobes, or dimpled chins, or widows peaks, etc... Basically there are thousands of differnt attributes a person can have that are mostly neutral to the health of the person, there are just random mutations that are niether selected for or agaisnt.

It jsut has to due with random mutations and natural selection, except in this case there is no selection becasue the attribute has no effect on survival. Of course it is always helpfull to have these random mutations around because its possible that a deadly virus comes along which people with the 'A' antigen are immune too, and then humasn will eventuall adapt to be less susceptible to that pathogen. For example there is a slight mutation in some gene that was very rare 20 years ago and served absolutely no known putpose, but it turns out that it makes you immune to AIDS, so now people have done studies where prostitutes in African countries (who are very likely to be exposed to AIDS) have a much higher occurance of the mutation than msot because the ones who didnt have it are obviously dying off.

 

[Peter]

You'll also have to mind that there are MANY more differences to individuals' blood than just the popularly known "type".

 

[Gigantopithecus]

Sorry, but those of you arguing blood groups are neutral or evolutionary remnants are just plain wrong. There are literally dozens and dozens of different types of blood types, each determined by specific, gene-level differences - they're all polymorphic. Most of them are adaptations to different types of diseases.

Aside from the well-known ABO & Rh(esus) groups, there are the Duffy, MN, Diego, Colton, Kell, Lutheran, Lewis, Xg, Bombay, S (sickle cell)... The list goes on and on. If memory serves all of them have at least some hypothetical reason for variation. Others, we know for sure exactly why they've evolved some variability. I'll list & describe some of those here:

ABO: This blood group has three alleles, A, B, & O. A & B are codominant, O is recessive; there are four phenotypes: A, B, AB, & O. B & O phenotypes are more resistant to such pathogens as venereal syphilis, B is more resistant to plague, A is more susceptible to smallpox, etc. Perhaps more importantly, the different phenotypes experience what's called prezygotic selection - sperm of certain blood groups are less likely to fertilize ova of another; for example, non-O sperm (A, B, or AB) are less likely to fertilize an O ovum than are O sperm. Haldane recognized in the 40s (I think) that this type of prezygotic selection can actually drive speciation - so this isn't just microevolution we're talking about here.

S: Sickling is a common adaptive response to malaria; there are multiple types of sickle cell (different alleles), but the most common is the S allele. Here, there are three genotypes: AA (normal hemoglobin, normal red blood cells), AS (sickle cell trait, red blood cells sickle under certain stressful conditions), and SS (sickle cell anemia, red blood cells sickle most of the time). AA has no resistance to malaria caused by Falciparum organisms, AS has a very high resistance to Falciparum malaria (relative to AA), and SS is nearly 100% lethal before the carrier reaches adulthood. Thus, the S allele is most frequent in areas of the world where malaria is endemic (sub-Saharan Africa, the area around the Mediterranean, Southeast Asia) - there is no advantage to having an S allele where there is no malaria, because there's no malaria danger to outweigh the dangers of having either sickle cell trait or sickle cell anemia. The S allele is a fantastic example of what's called a balanced polymorphism. You can read more here, from the man who recognized the adaptive nature of sickle cell anemia over 50 years ago.

Duffy: Duffy has three alleles: FyA, FyB, & Fy (the recessive). Individuals who are FyFy are nearly 100% resistant to malaria caused by Vivax - further, there are no known ill effects of being FyFy (unlike AS or SS, where AS can have problematic sickling and SS is lethal). Frequency of FyFy is at or very near to 100% in certain populations, like the pygmies of Western-central Africa - vivax malaria, unsurprisingly, simply doesn't affect those populations, because they're completely resistant. FyFy individuals are practically non-existent in people from Northern Europe & Northern Asia - the Fy allele probably hasn't had time to make its way into those populations, and while there's no disadvantage to being FyFy, there's no advantage to it where there's no vivax, so this is not a balanced polymorphism.

If you want to read more about blood groups & their evolution, check out Molnar's Human Variation: Races, Types, and Ethnic Groups or Relethford's The Human Species: An Introduction to Biological Anthropology. Non-current editions can probably be had on Amazon for pennies.

 

[Gibsons]

eh, good points, but...

I'll still argue, as I said, that blood types in today's world are mostly neutral (note the qualifier!). Not in areas of endemic pathogens that infect red blood cells (malaria), but that's a minority. Call it "the exception that proves the rule." Basic question is "do different blood types affect an individuals ability to reproduce?" Outside of areas with endemic malaria (or perhaps other, it seems to me the answer is usually no.

As for other diseases... smallpox isn't an issue for anyone. Syphillis (and even plague) rarely if ever, affects someones reproductive potential (at least in this century). Furthermore, I'm willing to bet the resistance provided by different blood groups is miniscule, if it exists at all. It's certainly small enough to not be mentioned in most literature on syphillis (I couldn't find any data on this, would appreciate being pointed to some) and certainly people with blood type O contract syphillis with exposure. Also, these data could easily be correlative rather than causative. The blood type alleles could be linked to some other allele that's actually providing the protection, especially in such a case where the mechanism by which it might work is unclear.

Prezygotic selection is another matter entirely, but is the effect really that strong (I've read about it, but can't recall any numbers whatsoever)? And again, how confident can we be that we aren't looking at the effects of a linked allele instead? Are the blood group antigens expressed on sperm or eggs?