How you and I are responsible for Flat Earthers, Anti-Vaxxers, and Fake News

I.

There is a concept in biology known as Heterozygote Advantage. If you’re already familiar with this concept, feel free to skip to section II.

As one may know, sexually reproducing organisms inherit two copies of each gene: one from the mother, one from the father. Sometimes having two identical copies doesn’t mean much. Sometimes it means a lot. Having one recessive allele (gene variant) and one dominant allele usually means that the recessive one can be passed on along with the dominant one, but the dominant one is the one that is presented in the organism. For example, if a child inherits one blue-eyed allele and one brown-eyed allele, the dominant brown-eyed allele is the one that drives (so to speak) the phenotype (the way the organism biologically presents its genes) while the recessive blue-eyed allele rides shotgun, serving no function in the organisms per se but maintaining the possibility of being the one that is passed on to this organism’s offspring when it’s time to send one of the two genes into the next generation’s car, to continue the metaphor.

Say hypothetically that there’s a recessive gene that allows people to heal really quickly. If you inherit only one copy of this gene, since it’s recessive, the dominant “normal healing” gene is the one that is presented in the organism, and there’s no biological difference from someone not having the “quick healing” gene. If, however, an organism has two parents who have this recessive “quick healing” gene, and happens to inherit both copies, then this child would have the Quick Healing trait. This child could get in deadly car crashes and be more likely to survive, be shot on a battlefield and be able to heal before bleeding out, etc. Even if this child never got an adamantium skeleton and never gained the ability to eject and retract blades from his hands, this child would be more fit — more likely to survive into adulthood and pass on genes — than one who did not have this genetic combination (ceteris paribus). This would be, for most intents and purposes, a good genetic combination to have (leaving aside the fact that in many organisms in nature, quick healing attributes are correlated with higher propensity for cancer). We would say in this situation that this organism has a Homozygote Advantage. This means, there is an advantage to having both copies of a gene where there is not an advantage to having only one.

Then we have the opposite concept: a heterozygote advantage. As one may be able to infer from the above idea, a heterozygote advantage is one in which it’s more beneficial to have only one copy of an allele than two. The classic example of this is Sickle Cells: one copy of the gene that produces sickle-shaped blood cells makes red blood cells less susceptible to attack by the parasitic plasmodium that causes malaria, conferring an advantage in fitness. Having two copies of this same gene, however, makes too many blood cells two misshapen; the circulatory system struggles to deal with this complication, and Sickle Cell Anemia results, usually ending in premature death. This is a homozygote disadvantage, or a heterozygote advantage.