Underwhelmed by conscious choice

The genetic mutation that causes sickle-cell anemia also increases one's resistance to malaria. But whereas sickle-cell anemia is a recessive trait—meaning that to get the disease you must have two copies of the mutation—increased resistance to malaria is a dominant trait that comes from having only one copy of the mutation. Therefore, the optimal strategy for individuals living in an area with a high incidence of malaria is to have a single copy of the sickle-cell mutation, thus gaining resistance to malaria without the early death brought on by sickle-cell anemia.

The problem with this strategy is that if too many individuals pursue it then individuals suffer as a group. People who have a single copy of the sickle-cell mutation are carriers of the disease, and an offspring of two mated carriers has a one-in-four chance of having the disease and a one-in-two chance of being a carrier. An offspring of a carrier mated with a non-carrier has no chance of having the disease. So even though it's better for an individual to be a carrier and benefit from increased resistance to malaria, it's better for the group to have a mix of carriers and non-carriers, thus reducing the incidence of sickle-cell anemia. As with prisoner's dilemma, there's a best solution for the group that's in conflict with the best solution for the individual. How many other prisoner's dilemmas are lurking in our DNA?

For most of our species' history, we have benefited from mindless Nature solving our genetic prisoner's dilemmas for us. When the optimal solution is a mixed strategy, such as in tropical zones with regards to the sickle-cell mutation, Nature does an OK job of selecting for the mixed strategy. Without a mind to overthink the problem, or to pursue fashions or Faustian gains, Nature finds a balance between two diseases.

So when I hear that designer babies are on the way, Gattaca-style, and that some couples are already choosing the sex of their babies, I'm not struck with overwhelming confidence that this is a smart move over the long run—not until we're consciously able to deal with prisoner's dilemmas as well as mindless entities do.