The positive productivity contribution of market selection declines gradually, both because the failure rate decreases with age and also because the productivity gap between the exiting and surviving firms narrows.
The decay in GST was similar for markers linked to ecological loci and inversion haplotypes, whereas values for markers that were not linked to loci under selection declined more rapidly and to lower values after 1000 generations.
One of the major ideas in the evolutionary theory of ageing [36] is the suggestion that, because the force of natural selection declines with age, alleles with deleterious effects seen only at older ages can reach higher frequencies than those that have their effects earlier in life [37].
One prediction is that fast aging should evolve if the strength of selection declines quickly with age, and slow aging if the strength of selection declines slowly.
Variance in total relative fitness declined steeply over time (average up to 1974, 10.5 × 10−2; 1975 onward, 7.34 × 10−2; overall Spearman's correlation, ρ = −0.75; p < 0.001; Figure 1A), indicating that the opportunity for selection declined.
This second trend arose because the contribution to response to selection declined more rapidly for GS than for PAGE, due to the greater impact of genetic drift and hitchhiking on the loss of favourable alleles in the GS only scenarios.
Nonetheless, the force of selection declines steeply starting at the age of first reproduction simply because some individuals die each year, even in the absence of aging and cancer.
However, as delineated by Hamilton (1966), this class of models, because of the Malthusian condition they implicitly assume, entail that the intensity of selection declines with age a property which is inconsistent with the existence of mortality plateaus, that is, the deceleration of mortality rates at extreme ages.
First, treating juvenile traits as traits of the mother, if the strength of selection declines with increasing age and thus inbreeding depression increases with age, we might predict that maternal inbreeding coefficient should interact with age such that there is an increase in inbreeding depression on juvenile traits in inbred mothers at older ages.
Second, gene losses continued to prevail over gene gains in the later evolution of bony vertebrates (see Section 2.8), and the number of branches under positive selection declined in a gradual way along the evolutionary path from 2R-WGD to the mammal radiation (see Section 2.9).
But NASA delayed it again, this time to no later than January, which it said would "allow time to complete a thorough proposal evaluation and selection". It declined to comment further.
