Because there is a major selective disadvantage to individuals with more mutations, these individuals die out.
2.
Loss of this trait need not necessarily confer a selective advantage, but may be lost due to the accumulation of mutations if its loss does not confer an immediate selective disadvantage.
3.
Ralph Holloway of Columbia University argues that the new research raises questions about whether the variations in skull shape have " adaptive meaning and whether, in fact, normalizing selection might be at work on the trait, where both extremes, hyperdolichocephaly and hyperbrachycephaly, are at a slight selective disadvantage ."
4.
Stepchildren were seldom or never so valuable to one's expected fitness as one's own offspring would be, and those parental psyches that were easily parasitized by just any appealing youngster must always have incurred a selective disadvantage " ( Daly & Wilson, 1996, pp . 64 65 ).
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