Asymmetric developmental bifurcations in polarized environments: a new class of human variants, which may include autism.

Inspired by discrete stable alternative states that often coexist with the dominant phenotypes of a species, we propose that asymmetric developmental bifurcations (ADB) may provide a biological framework for grouping autism together with some human alternative organizations rather than with disorders or diseases. These include minority embryological or obstetrical variants, such as twinning and breech presentation, as well as minority information processing variants, such as left-handedness and importantly prototypical autism. Four common contextual, developmental, adaptive, and mechanistic features unify these alternative conditions as ADBs: 1) ADBs occur in a dynamic system formed by an individual and his environment with two polarized stable solutions. 2) The bifurcation occurs in a critical period of development and is significantly shorter than the stable states that precede and follow it. 3) While the frequent branch of the ADB optimizes evolutionary success, its rare branch has an adaptive cost, which is still compatible with survival. 4) Both rare and frequent branches of the ADB are human possibilities, favoured without major/deleterious changes by familial and/or sexual predispositions. Framing autism as a categorical, alternative phenotypic prototype in a polarized choice between social bias and its absence, elucidates autism's recurrent divergence within the species, its developmental and information processing characteristics, and its adaptive challenges.