[username90]

Did they actually do a twin study on finger count, or are you making things up? Otherwise you can't know for sure. For example, I'd bet that propensity to lose limbs correlate strongly with willingness to engage in risky activities, and risk taking has a significant genetic component according to other studies.

[travisp]

Even if you're right (and finger count is a common example for students to teach the concept of heritability), this will run counter to what people think when they hear "heritability."

Most people wouldn't think "number of fingers is heritable because their propensity for risk taking is genetic" they would say it's because the number of fingers we are born with is genetic, which would be a mostly incorrect reason for any heritability statistic on number of fingers. I think your possible explanation about why number of fingers might be fairly heritable only reinforces my point about what most people understand about heritability.

And, for the same reason, while risk taking seems to be heritable, we don't know the particular genetic contribution to risk taking.