I’m really having trouble wrapping my mind around the concept of heritability.
These numbers are obviously wrong, but let’s just use them for convenience:
Let’s pretend that scientists say that 80% of height is due to my genetics. If I’m 100cm tall, I understand that the scientist is NOT saying that 80 of my cm is due to my genetics.
I also understand that it doesn’t mean that if there are 100 people in my population, it doesn’t mean that 80% of them are only as tall as they are because of their genetics.
Does it mean that 80% of the reason I am as tall as I am is because of my genetics?
I started wondering about this when someone mentioned something to the effect of, “If your dad was a drinker, it runs in the family.” and also things like, “you’ll probably go bald because your mom did”. I understand that heritability is a term used for population studies, but I’m not sure why it doesn’t apply to individuals as well.
And if you read this and think “hoooo boy, OP’s gotta go ALLL the way back to square 1”, I’m more than happy to click a link and read!
Thanks a lot for your help!
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>I understand that heritability is a term used for population studies, but I’m not sure why it doesn’t apply to individuals as well.
Well, it *does* apply to individuals.
/u/lollersauce914 has a solid explanation on the nature of your 80% figure: namely that once you separate and control for different sources of variation, genotype hypothetically accounts for 80% of the total variation.
This is something that you can only realistically figure out from large population studies, but the biological mechanisms are very much at play in every single individual. Height is complicated because it’s influenced by many genes and environmental factors, but with sufficiently detailed understanding of their interplay, you totally could take that general knowledge and extrapolate back to individual cases.
This is the basis of much of modern life sciences & healthcare; figuring out exactly how biological systems work (we call that “mechanisms”) and then engineering precise interventions to steer things in a more desireable direction.
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