rhettsmith.com

Rhett,

Howdy. Excellent find.

Red flags should go up whenever one reads a report that claims that some trait or other is n% genetically determined. Much of the time, claims like this don't make any sense. I'm not saying that they are usually inaccurate---I'm saying they usually literally don't make sense.

Here's an analogy that Ned Hall gives to students in his philosophy of biology class at MIT. Jack and Jill are going to fill a pail with water. Consider two scenarios. In Scenario 1, Jack and Jill both bring their own containers of water and pour them into the communal pail. In this scenario it might make perfect sense to say something like "Jill contributed 40% of the water and Jack contributed 60%". In Scenario 2, Jack turns the water valve on, and Jill directs the hose into the pail. In this scenario, it clearly wouldn't make any sense to say that Jill contributed 40% of the water and Jack contributed 60%. The interaction between genotype and environment that produces phenotypic (trait) variation is more like Scenario 2 than it is like Scenario 1. Sometimes good sense can be made out of assigning percentages to the genetic and environmental contributions, but several assumptions have to be satisfied first---assumptions that are seldom satisfied (additivity, for example)...

Twin studies are also controversial for many reasons. One of them---not necessarily the most important or telling---is that it is assumed that fraternal twins who are raised together have environments that are as similar as those of identical twins who are raised together. You can probably think of reasons for doubting that this is the case; and experimental data has also cast doubt on it.

Still, however, it's not like the cited study isn't interesting. I looked up the journal article and gave it a skim. The data is interesting and surprising. They jury should still be out on how to interpret it, but I think it shouldn't be ignored.

Thanks for directing our attention to this article. Quite interesting.

--jason

P.S. Did you see the link on that page to this letter: [http://www.newscientist.com/article.ns?id=mg15420826.900]? It's kind of amusing. The closing line: "In other words, the more intelligent and educated a person is, the less likely that person is (on average) to be religious."

Jason, you are the smartest person I know! I love the Jack and Jill analogy.

Late to the game. I was reading an article in Time or what not and they were talking to scientist about religion and something like 80% of all scientists belive in a God or higher power? Seems to be a serious contradiction to the quote

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