Vivian – African pygmies do not live in deserts; these tribes are indigenous to the rainforests of western Africa.

Both Vivian and Cameron are confusing proximate versus ultimate explanations. Both can be correct at the same time. Proximate explanations look at the mechanisms that cause the phenomenon in question. Ultimate explanations – which is the level of inquiry for the study – examine how the force of natural selection may favor the change we see.

A large boned heavy pale northern person would expire quickly in the desert where an African pigmy can thrive. An African pigmy would die quickly where the large northerner would thrive.

In some family genetics, the boy stays small and then does a rapid growth at 15-16. (perhaps to be allowed to reach the age of maturity left over from more violent times) In other families, the boys grow evenly over the span of their childhoods.

I would assume that some of the factors that explain life expectancy also individually help explain height and, because life expectancy encompasses some of these factors, the analysis may represent these other factors as being less significant than life expectancy in explaining height variation.

At the end of the day life expectancy may still be a good way of predicting height variation but it would seem wrong to conclude that it is life expectancy driving the variation in height and not the factors that contribute to life expectancy. I’m sure some of the factors that contribute to life expectancy also contribute to age at onset of puberty and other developmental stages.

I do admit I haven’t yet read the study or looked over how they chose to model the data and analyse the statistics. I’ve been trying to get through the back-log of posts in Google Reader and now’s not the time to get bogged down with only 245 more entries to read through!