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!
In: 2
Some of our physical features are determined directly by our genes. Eye color, for example, is directly coded in our DNA, which instructs cells how to come together and make proteins and pigment and other necessary building blocks. This DNA is a combination of our parents’, and so the genes that determined their eye color influence ours as well.
However, some traits are a mix of genetics and outside influences. This includes height, weight, and likelihood of getting various cancers, among other things. While our DNA has a large part in dictating these features, they are also affected by our lifestyle and environment.
To go back to your requested subject of height- if you give a child the bare minimum of calories and nutrients necessary to survive for their formative years, it is unlikely that they will grow to be very tall. Their body didn’t have the resources needed to fund more growth, with all of the energy being directed to keeping that child alive. Some medications slow growth, and some environmental chemicals will affect this as well. The amount of exercise the child gets will also affect muscle and skeletal growth.
However, (using your numbers) if 80% of height is determined by genetics, that means that if you compare the heights of many different people, about 80% of the variation in their heights can be predicted by their genetics. Many different genes (coded by inherited DNA) combine to give you a rough estimate of the height that their body can achieve, while about 20% of that variation can be predicted by their diet, exercise, and environment. The genetic effects are weighted much more heavily in determining height than environmental and lifestyle effects.
Latest Answers