GOOD GENES AND OLD-AGE - DO OLD MATES PROVIDE SUPERIOR GENES

It has been suggested that female preference for older mates in specie s without parental care has evolved in response to an alleged higher g enetic quality of older individuals. This is based on the widespread a ssumption that viability selection produces older individuals that are genetically superior to younger individuals. In contrast, we propose that the oldest individuals rarely are genetically superior. Quantitat ive genetic models of life history evolution indicate that young to in termediately aged individuals are likely to possess the highest breedi ng values of fitness. This conclusion is based on four arguments: 1) V iability selection on older individuals may decrease or at least not s ubstantially increase breeding values of fitness, because there may ex ist negative genetic correlations between late-age and early-age life history parameters, 2) Fertility selection is likely to raise the fitn ess of gametes produced by young individuals more than those produced by old individuals, because the covariance between fertility and fitne ss often decreases with age, 3) The history of selection on their pare nts makes younger individuals more fit than older individuals, 4) Germ -line mutations, which are generally deleterious, significantly decrea se the breeding value of fitness of an individual throughout its lifes pan, especially in males. Therefore, females that mate with the oldest males in a population are doing so for reasons other than to obtain o ffspring of high genetic quality.