The 400m British champion Nigel Levine, the 60m hurdles champion Andy Pozzi and the 1500m champion Hannah England also declined selection in favour of concentrating on the outdoor season.
To investigate further possible reasons for declining selection pressure within Gag epitopes with progression to AIDS, we considered the hypothesis that loss of CD8+ T-cell responses as CD4 count declines results in reversion of escape mutants, with resulting increase in viral replicative capacity.
The qualitative results of impeded selection due to culling still apply, but as degree of resistance declines, selection will be slower and the frequency of the resistance allele will ultimately be higher (to achieve the same degree of overall fitness), provided that degree of resistance is above 0.66 (Figure 3).
We found a significant relation between mean and maximum life span among mammal species (R2 = 0.57, p<0.0001; Fig. 1A), supporting the hypothesis that rate of decline in selection pressure (as estimated by survival and mean life span) is a determinant of rate of senescence and hence maximum life span.
The mean life span of adult individuals in a wild population, which can be calculated from estimates of survival probability, is a robust index of the rate of decline in selection pressure with age for species with determinate growth, like mammals.
This theory proposes that aging has evolved as a consequence of an age-associated decline in selection pressure, permitting genes with late-life deleterious effects to be positively selected if they confer an advantage early in life (Williams, 1957).
We hypothesized that the reduction in breadth of CD8+ve T cell responses might result in, and therefore correlate with, a decline in selection pressure, particularly in Gag in light of the relative shift away from Gag targeting.
However, this concept is unsatisfactory because only the gradual decline of selection pressure is considered, but not the fact that the state of the organism at one age is tied to the state of the organism at preceding and subsequent ages, which takes away degrees of freedom from the patterns of senescence that can evolve.
Using the mean value of I in Table 2, heritability of relative fitness would need to be >0.07 (0.3/4.5) for males and >0.09 (0.3/3.5) for females to explain the 30% fitness decline, assuming selection attributed to the hatchery operated directly on the 'trait' of relative fitness in the wild.
"Korean?" he asked when I declined his selection.
