Blood Types – Chance or Design?

Here’s a genetic oddity….. Why do we have different blood types?

One would think that human blood would be the same all over. It’s a commodity product. It is there to do a job. It delivers nutrients throughout the body, delivers oxygen and removes carbon dioxide, staves off infections, and 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 due to the varying antigens on the surface of red blood cells. Type O is the most common, with approximately 45% of the population in this group; type A, 40%; type B, 11%; and type AB, 4%.

There is also a geographical and ethnic variation. In general, Caucasians are mainly type A; Asians are mainly type B; and Africans are mainly type O. It is noticeable that island and indigenous populations have lower blood type mixtures. The Bororo tribe in Brazil is 100% type O. Other blood groups have not taken hold in these communities. More blood group variation seems to occur in more dynamic populations.

Given that blood groups are a relatively recent discovery (Karl Landsteiner in 1900), this variability may suggest 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 suggests there must be a reason for it.

And yet, there’s nothing immediately apparent about why different blood groups exist or would be beneficial. No obvious or compelling advantage is conferred.

Research has shown that different blood types can offer some marginal protection against certain diseases, such as type O blood protecting against malaria. However, it does seem that blood group is not the main factor in determining whether an infection is caught, the survival rate from the infection, or 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 an advantage to having a particular blood type, then, as a survival trait, it would have become much more prominent in our partner selection and reproductive processes.

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 to make it a factor in mate selection. If it were, 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 were important, it would also be mandatory to include 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 influence our choice of reproductive partner more readily – health, status, wealth, personality, physicality.

Given that this blood variability is not unique to our species, this suggests it is not a chance occurrence but has been intentionally established. 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 our eggs in one basket. Nature is spreading the risk.

Having different blood types is therefore a defensive mechanism, a form of backup protection should the species be threatened by some viral force.

Different blood groups have been created, encouraged, and maintained 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 were, it would receive greater prominence in our selection of reproductive partners.

Nature may have deemed that there are other, more pressing priorities that need to be addressed. 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 who earn the points are usually more valued than those who prevent points from 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 criterion could become much more significant and a key consideration in our survival as a species and in our future selection of reproductive partners.

For other interesting blogs on this subject area, check out Articles or the Article Index