Here’s a genetic oddity…. Why do we have different blood types?
You would think that human blood would be the same all over. It’s a commodity product. It is there to do a job. It dispenses nutrients through the body, it delivers oxygen and takes away carbon dioxide, it staves off infections and it carries hormones.
Yet we have four main blood groups – broken down into eight types which are largely incompatible with one another. The differences between them are down to the varying proteins on the surface of the red blood cells called antigens. Type O is the most common with approximately 45% of the population in this group; type A would be 40%; type B 11% and type AB 4%.
There is also a geographical and ethnic variation. Very generally; Caucasians are mainly type A; Asians type B and Africans type O. It is noticeable that island and indigenous populations have lower mixes of blood types. The Bororo tribe in Brazil is 100% type O. Different blood groups have not obtained a foothold in these communities. More blood group variation seems to occur in more dynamic populations.
Given that blood groups are a relatively modern discovery (Karl Landsteiner in 1900) this variability may be suggestive of a genetic work in progress. Having different blood types may in genetic terms actually be a recent phenomenon. That being the case, with time, the prevalence of groups O and A may gradually diminish and the ratios between the groups may become much more aligned.
Strangely, variability is a peculiarity of our blood. There is not the same variability between other parts or organs of the body; kidneys are universal as are hearts and lungs. Nor is this blood variability specific to us. Other species also have different blood groups. This would suggest there has to be a reason for it.
And yet, there’s nothing immediately apparent as to why different blood groups exist and would be beneficial. No obvious or compelling advantage is conferred.
Research has shown that different blood types can offer some marginal protection from certain diseases such as type O guarding against malaria. However, it does seem that blood group is not the main factor in determining whether or not an infection is caught, what the survival rate from the infection is or in determining the severity of the infection.
Blood groups like the colour of a person’s eyes are an inherited characteristic. A child’s blood group will depend on the blood types of its parents. But why do we get the variation? Why is it necessary?
If, within a specific environment, there was some advantage to be gained from having a particular blood type, then, as a survival element, it would have become much more prominent in our partner selection and reproduction process.
Blood type variation has no visible representation. We can’t see any difference between people with different blood groups. As such, it cannot be a major influence in our selection of a reproductive partner. Nature does not deem it sufficiently important enough to make it a factor in mate selection. If it was then, quite frankly, it would be reflected in some visible characteristic.
Similarly, we don’t tend to make a great thing of it ourselves. If it was important, it would also be mandatory information to be completed on any dating profile form!
Blood type has never been and seems unlikely to ever be at the top of that selection list. There are other more apparent factors that tend to more readily influence our choice of reproductive partner – health, status, wealth, personality, physicality.
Given the fact that this blood variability is not unique to our species, this suggests that it is not a chance occurrence but has been established by design. Although this adaptation will have initially occurred by a chance mutation, it’s a development that Nature has deliberately seized upon. Our genes must see some worth in having this variation. After all, Nature doesn’t waste its efforts. Nature always has a reason.
It may be that although we are 99.9% genetically identical, Nature recognised that we had a vulnerability and that, within reason, it was important to maintain some variation within the species. It is therefore a form of protection in case the species comes under attack. It’s a classic case of not putting all your eggs in the one basket. Nature is spreading the risk.
Having different blood types is therefore a defensive mechanism, a form of back-up protection should the species be threatened by some viral force.
Different blood groups have been created, encouraged and maintained in order to ensure some diversification within the species. It’s like the gambler at the roulette wheel who spreads his chips over a range of colour and number combinations. Nature has, similarly, hedged its bets.
So, although Nature may have recognised the value of different blood types, in the scheme of things, encouraging blood type variation is probably not at the top of Nature’s to-do list. As we have noted, our blood type can hardly be considered a genetic priority, for if it was, more prominence would be given to it in terms of our selection of reproductive partners
Nature may have deemed that there are other more pressing priorities that need addressing. So, any genetic adaptations focus on these rather than on our blood type.
The nature of genetic adaptation is such that short term gains will be seized upon more readily than any longer term, less obvious benefits. Similarly, adaptations that are more proactively advantageous are much more attractive than those that are defensive. Just like in a sports team, the players that earn the points are usually more valued than those that prevent points being scored against the team.
Hence, blood variation to ward off an unknown, unquantifiable remote possibility has not been at the top of the genetic action plan.
However, if a virus or threat did occur that relied on our blood’s make-up to defend ourselves then this criteria could become much more significant and a key consideration in our survival as a species and in our future selection of reproductive partners.