Every few years, when I teach general biology again, I get to discuss Mendelian Genetics and basic inheritance. Since I spent a great deal of time on it again this year, it reminded me about a concern of mine in the global age. Now that people can converse and interface like no other time before with people they only encounter with modern technology and travel, it begs a genetic question in the F-2 generation. I want people to understand the possible risks, to think of their grandchildren, and to make informed decisions. I want them to understand that chemistry does not discriminate.
Mendel crossbred his pea plants through what he called the 2nd Filial (F-2) generation for good reason. In essence, what he was doing was crossing lines of vastly different genetic propensity to determine how genes pass to posterity. Although he didn't make any genetic counseling recommendations, his work did show a fundamental truth. In populations of significant genetic variance, it is the 2nd Filial generation (or the grandchildren) where masked or hidden traits appear. In populations or in the case of traits where these cause significant medical consequence, in the grandchildren, diseases appear.
In almost every way, the freedom to love, date, and marry whom you choose is noble and virtuous. In the case of genetics, it should give you pause. I met a woman about 12 years ago whose parents were from Ghana and Nigeria, making her an exotic and beautiful hybrid that caught everyone's eye and appealed to the fancy of many. By the time I met her, she already had two children, both of whom had serious medical issues. Her third child cost her a significant amount of money setting things right. Essentially, she is the only member of her "race" or genetic haplotype, and neither of the men with whom she had children came from genetic pools compatible with hers. By the grandchildren of her parents, there was no compensatory mechanism to counter the problems caused by vastly different genetic pools.
Vast genetic differences do not mean that things must be worse than if you found a family with someone of similar genetic background. It means that there's a greater chance of a problem. Mendel showed us that the chance is never zero, however minute, when you mix two genetically different lines. It probably didn't happen before or manifest before because child mortality was high for other reasons. Now that health care provides for things caused by genetics, it becomes a financial matter, but it causes emotional pain.
Lots of people will leverage the emotional wedge of your posterity to dictate your actions. From a strictly actuarial point of view, if you care about the prospects of your posterity, consider very well whom you choose as a mate. I know everyone wants to look diverse or inclusive or open-minded, and I know everyone claims to care about their children. Picking a mate works best for your posterity when you are compatible in as many ways as possible. While it's true that opposites attract and that exotic is interesting, chemistry teaches us that compatibility matters most, and Mendel teaches us that genetics masks problems only to manifest in those distal to us in space and time. They are not distal to our hearts, and if you care about your F2 or F3 or F30 generation, choose wisely your mate.
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