  This paper suggests that the fundamental haploid-diploid cycle of eukaryotic
sex exploits a rudimentary form of the Baldwin effect. With this explanation
for the basic cycle, the other associated phenomena can be explained as
evolution tuning the amount and frequency of learning experienced by an
organism. Using the well-known NK model of fitness landscapes it is shown that
varying landscape ruggedness varies the benefit of the haploid-diploid cycle,
whether based upon endomitosis or syngamy. The utility of pre-meiotic doubling
and recombination during the cycle are also shown to vary with landscape
ruggedness. This view is suggested as underpinning, rather than contradicting,
many existing explanations for sex.
