Enhanced nutrition of offspring as a crucial factor for the evolution of intelligence on land.

Whilst life in the sea is undoubtedly an ancient process organisms with an exclusively marine lineage have not evolved the degree of intelligence demonstrated by the most advanced terrestrial species. Among the differences between terrestrial and marine environments which may begin to account for this is the instability of the terrestrial environment in comparison to the ocean. Unlike the ocean, terrestrial environments are not buffered against rapid changes in temperature, available water and other environmental extremes. This represents a challenge for the vulnerable offspring of terrestrial species. Evolutionary adaptation to this challenge has included greater transfer of resources from adult to offspring, as demonstrated by terrestrial vertebrates. However the evolution of mechanisms allowing enhanced transfer of resources between generations also creates conditions whereby offspring can be born with larger and more costly brains, developed and nourished from the outset even when they are not likely to prove useful until later life. As nutrition of offspring on land improved through natural selection better brains may thereby have been facilitated, with subsequent evolution driven by proximate selective pressures. The culmination of this process may be seen in the enormous transfer of resources from parents to offspring characteristic of humans and the advanced intelligence associated with them. Medical implications of this theory include the possible impact on the maternal brain of increased transfer of resources to the developing brain during pregnancy and lactation. This could help to account for the observed association between mental illness and the puerperium.