This is a common misconception

And a very weak argument.

There are several reasons why "maladaptive" traits remain in a population, most of which have nothing to do with psychological adaptations, kin protection or any EP-generated model:

1) recessive conditions are concealed in heterozigozity: cystic fibrosis, spinal muscular atrophy, phenylketonuria, none of these have been "eliminated" from the population and they probably never will.

2) The onset of the symptoms happens during or after the reproductive years of the individual, giving him/her plenty of time to pass it along.

3) Many conditions are determined by the interaction between different genes plus environment.

4) Several conditions are correlated with the age of the mother, the father, or both, at time of conception. State of health of the mother, substances she'd been exposed to before and during pregnancy.

There are also many cultural factors that we do not yet fully how, how they interact with genetic information. For example, we do not know yet how delayed reproduction in industrialized countries affects the oubreak of certain mental disorders in modern populations.

A few examples from my own family: from my ex- mother in law's 6 children, only one (my ex-husband, it had to be) came to develop a personality disorder. She was 42 when he was born. No one else in his family has been diagnosed with any psychological disorder (not even depression, which has become the rule rather than the norm). Of my aun's 3 children, only one has muscular distrophia, the one she gave birth when she was 40. My ex- sister in law gave birth to two children after she was 38, and both children have speech and other mild developmental problems.

It is a very naive belief, that maladaptive conditions come to be weeded out of the population just because they do not confer maximum fitness. Only dominant conditions that arise before, or early in the reproductive life of an individual will be erradicated.

Alex.

<4) Characteristics that appear maladaptive should be extinct by now. Schizophrenia and ADHD are with us and elicit speculations about their adaptive value. >

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