In his paper “On Heritabilty in the Presence of a Stochastic Environment”, Nassim Nicholas Taleb discusses a fundamental issue with the way heritability studies, such as twin studies, are conducted. Twin studies often aim to measure the heritability of traits by comparing the correlation between identical twins to that of fraternal twins. This comparison is supposed to eliminate environmental factors and isolate the genetic component.
The problem, according to Taleb, is that these studies typically ignore the role of differing environments. He provides an example where the heritability of diabetes might be calculated differently in a city like Minneapolis versus the Kalahari desert. While identical twins in Minneapolis may share a high correlation for diabetes, that correlation could be much lower in the desert, which would affect the overall heritability estimate. This demonstrates that correlation can change based on environmental conditions.
Taleb then proceeds to discuss the mathematics behind correlation, indicating that it is often used unconditionally, but the results can be vastly different when considering different conditions. He argues that we need to take into account these different conditions (or environments) when calculating heritability.
In other words, Taleb is suggesting that the environment, and how it changes, can play a much larger role in the heritability of traits than is currently accounted for in twin studies. These studies might overstate the degree to which traits are heritable due to their methodology.
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