How can elves prevent specialization among their species?

Question

Genetic chimerism is a condition in which a single organism is composed of cells with more than one distinct genotype. Elves inhabit this world, but do not possess magic in this reality. Instead, they are all what can be genetically considered chimeras because they have a strange way of reproducing. When partners decide to conceive, a male must add his genetic material at different intervals throughout several years to the female. Genetic material could come from a single male or various ones with no connection to each other. Through this method, The developing child is slowly "built" with the genetic material of one father, or the makeup of several different fathers.

After enough "material" has been collected, the embryo becomes fully formed and the gestation process can begin. This method led to a lively "trade" in customized child production. Families and clans select and breed for distinctive traits that they consider valuable in political and economic agreements. However, this can be a danger to the Elven race. With clans selecting traits they themselves see as useful, this can lead to bottlenecks and a loss of genes within the species. It would also lead to specialization, which could be detrimental to their effectiveness and survival if their environment changes.

What mechanism can I include to prevent this from happening?

Answer 1

For any sentient species that isn't genetically hidebound to its ways, culture will move faster than genetics. That which is desirable and fashionable for one generation will not be for the next generation. Population preferences will shift, clan bloodlines will rise and fall in desirability, and the inheriting generation may try to push things in entirely different direction.

With it taking multiple years to produce even one child, I'd expect the elves to be evolving toward any particular popular genetic specialization significantly slower than humanity could.

Answer 2

It looks to me like you've already added the mechanism.

With clans selecting traits they themselves see as useful, this can lead to bottlenecks and a loss of genes within the species. It would also lead to specialization, which could be detrimental to their effectiveness and survival if their environment changes.

So, essentially this is the same issue as inbreeding in humans, with the slight twist that it does have short-term positive effects. However, you can even find instances in which inbreeding did have short term positive effects in humans. They were just political rather than genetic; European royalty for example was rife with it. What happened? Well, eventually the groups that engaged in it mostly died out as the costs accumulated. Groups with strong social stigmas against inbreeding generally did better.

This is a generalized evolutionary solution to most questions of the form "we have a long term negative choice that might have some short term benefits." Social stigmas are randomly allocated, and societies that don't end up with ones that are useful in the long term tend to die out or adopt the useful stigmas.

As long as the deleterious effects accumulate upon themselves while the meritorious ones stay constant, you'll always have a situation where eventually a dead end is hit.