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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> 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?
Frame it this way: Everyone falls somewhere on the distribution of heights that humans can have. What determines where any given person falls on this spectrum? Well, there are lots of factors such as diet (i.e., were you malnourished). In a statistical model you can isolate the impact of each of these various factors and calculate what percentage of the variation across people can be attributed to each. The hypothetical scientists are stating that 80% of the variation in height comes from differences in genetics between people.
> 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.
Yeah, these types of percentages, as outlined above, are about describing populations, not individuals. Of course there are ways to look at individual’s risk of various conditions and what not due to genetics quantitatively, but this usually involves less complicated traits than height.
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