Do you have a reference? It would be hard to establish causality. Genetic drift extremely important in megafauna due to very small population size. Selection ha

Do you have a reference? It would be hard to establish causality. Genetic drift extremely important in megafauna due to very small population size. Selection has to be exceedingly strong. Read Mike Lynch’s lovely paper in PNAS in 2007 (free from PubMed)—The frailty of adaptive hypotheses for the origin of organismal complexity. There is a high risk of “just so” stories to “explain” biological processes and phenomena. Nassim Taleb’s Black Swan well worth reading; Chapter 6 in particular.