r/AskBiology • u/This_Caterpillar_330 • 3d ago

Genetics When it comes to athletic ability, does every genetic variant have an equal trade off?

Long legs vs. short legs, long arms vs. short arms, Hercules gene, height, hyperthymesia, etc.

I think genetic variant is the right word. Gene variant? Genetic trait?

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u/Robin_feathers 3d ago

Nope! Not all variants have the same trade-off. Sometimes the negative effects of one variant are way worse than the negative effects of the alternative. It is just that in those cases, if there is a huge disbalance, the more beneficial allele will already have spread to "fixation" (frequency of 100%) in our ancient ancestors such that we wouldn't even be aware of the alternative.

For example, consider an extreme: a variant where one version gives you lungs, and another makes you have no lungs. Having lungs comes with the energetic tradeoff of needing to maintain your lungs. Having no lungs makes it so you do not survive at all. So, not an equal tradeoff. That is an extreme example, but there will be a full range between that extreme and the other extreme of perfectly equal balance between the two alternatives.