The dichotomy between @entity161 and @entity13521 is, as E. Kraepelin suspected, flawed; no unequivocal separation can be achieved. There are no categories of @entity716 , but only continua of variation. However, the definition of nuclear symptoms by K. Schneider reveals the fundamental characteristics of the core syndrome--it is independent of the environment and constant in incidence across populations that have been separated for thousands of years. The associated genetic variation must be as old as @entity1 and represent a component of diversity that crosses the population as a whole. The fecundity disadvantage that accompanies the syndrome requires a balance in a substantial and universal advantage; this advantage, it is proposed, is the speciation characteristic of language; language and @entity716 have a common evolutionary origin. Language, it is suggested, originated in a critical change on the sex chromosomes (the 'speciation event'--the genetic change that defined the species) occurring in East Africa between 100 and 250 thousand years ago that allowed the two hemispheres to develop with a degree of independence. Language can be understood as bi-hemispheric with one component function--a linear output sequence--confined to the dominant hemisphere--and a second--parallel distributed sampling occurring mainly in the non-dominant hemisphere. This mechanism provides an account of the generativity of language. The significance of nuclear symptoms is that these reflect a breakdown of bi-hemispheric coordination of language, perhaps specifically of the process of 'indexicalisation' (the distinction between 'I' and 'you') of self- versus other-generated references. Nuclear symptoms can be described as 'language at the end of its tether'; the phenomena and population characteristics of the nuclear syndrome of @entity161 thus yield clues to the origin of the species.

Is XXXX the price that @entity1 pays for language?

@entity1 :: ('9606', 'Species') :: ['Homo sapiens'] @entity161 :: ('MESH:D012559', 'Disease') :: ['schizophrenia'] @entity716 :: ('MESH:D011605', 'Disease') :: ['psychosis'] @entity13521 :: ('MESH:C564108', 'Disease') :: ['manic-depressive illness']
@entity161 :: (MESH:D012559,Disease) :: ['schizophrenia']
