I don't think Pinker is arguing that these are conscious determinations on the part of the rapist but rather that the genetic/behavioural/psychological traits which give him the impetus to rape also shape his choice of victim. And if we are to allow a genetic component may be a factor then it makes sense that the victims should be those suitable for reproduction.
After all you will notice Doddy says it is the genes' last ditch effort to pass themselves on, not the rapist's last ditch effort to pass his genes on.
TTFN,
WK
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