What is heretability exactly?


Or better explained. I probably don’t understand the concept fully. I cannot grasp how the heretability of certain traits (e.g intelligence) can increase over time. Thanks for your answers.

In: Biology

Heritability refers to the ability of a trait to be passed down, and it can be divided up into genetic and social heritability.

The genetic component, fairly obviously, is purely physical. And it varies dramatically from one trait to another. If you are talking about about eye color, then that is genetic heritability pure and simple. But topics as complicated as intelligence cannot be defined so simply. Most of what is going to end up affecting someone’s ultimate level of intelligence is social, with knowledge and mannerisms passed from one source to another.

Barring extreme cases like genetic developmental disorders, the effects of genetics on intelligence appears to be much, much less than the effect of one social condition, to the point of being essentially negligible.

You are talking about the [Wilson Effect.](https://www.cambridge.org/core/journals/twin-research-and-human-genetics/article/wilson-effect-the-increase-in-heritability-of-iq-with-age/FF406CC4CF286D78AF72C9E7EF9B5E3F/core-reader)

Heritability is when you ask “What is the proportion of the variation in a given trait within a population that is not explained by the environment or random chance?”

In a little kid, the environment explains a larger proportion of the variation in a given trait. So if you have one twin and send them to a good school and feed them healthy food, they will have a very different IQ than the twin you send to a bad school and inadequately feed. So maybe only 50% of the variation can be explained by genetics.

But say you check in with those twins again as adults. They are likely to have more similar IQs than when they were kids. Perhaps 80% of the variation is explained by genetics. Nutrition and school matters less as an adult, and genetics matter more when talking about the person’s peak IQ.

That heritability went from 50% to 80% (i.e., a 0.5 to 0.8 correlation). This correlates with an increase in age. So you can say that heritability increases with age. It’s just a weird way of phrasing it based on how the statistics from research studies are presented.