As a father the content of my conversations with friends and acquaintances has changed somewhat. Whereas in my offline life discussions of behavior genetics rarely came up, now they loom large implicitly and explicitly. Though the vast majority of people I interact with have graduate degrees or are pursuing graduate degrees in the life sciences almost none of them are aware of the magnitude of the heritability of most bio-behavioral traits.
For those of you who forgot, heritability is a population wide statistic which assesses the proportion of variation in the population you can attribute to heritable genetic variation. So if heritability is 1.0 all of the variation is due genetic variation; offspring are just a linear combination of their parents. If heritability is ~0.0, then there's basically no correlation between parents and offspring. Though, as I said, heritability is a population-wide statistic, it can be informative on an individual level. For example, the heritabiilty of height is ~0.90 in the Western world. To give you a sense of the expected height of the offspring of two individuals, just take the average (in sex-controlled standard deviation units) and shift it back toward the mean by 10%. There is going to be a lot of variation around this average. The rule of thumb seems to be that the standard deviation across siblings is roughly similar to the standard deviation within the population (though it seems to be a bit lower, with sibling I.Q. deviations being 2/3 of the magnitude of population-wide deviations).
Below the fold is a table reproduced from the paper Genetic Influence on Human Psychological Traits A Survey. Please do not read the table as a gauge of the "geneticness" of the trait. (whatever that means) Rather, it should give you a rough sense of the "pull" that biological inheritance will have on an individual. Biology may not be destiny, but it is definitely probability.
