Ecologists have been asking this question for several decades (e.g. [68]), often concentrating on intuitive life-history traits such as early reproduction, high reproductive output, or a non-specialized diet (reviewed by [69, 70]).
In addition to resource-dependent trade-offs, life-history theory predicts that in iteroparous organisms an increase in extrinsic mortality selects for optimal life history that shifts towards earlier reproduction, and higher reproductive effort [8].
Trophy hunting selects for smaller horn/antler size, delayed horn/antler development and earlier reproduction – influencing male reproductive success and the economic profitability of harvested populations (Festa-Bianchet 2003).
Additionally, when raised in a common environment, individuals from an invasive Spartina alterniflora population that had recently taken over open habitat on the west coast had earlier reproduction and higher reproductive effort, but also earlier mortality, than individuals from high-density native east coast populations (Davis 2005).
A shift in reproductive schedule towards earlier reproduction would be indicative of adaptation in our imposed life-cycle, while longevity is expected to evolve as a response to the harm that males impinge on hermaphrodites upon mating.
Although these worms compensated for lost early reproduction by increasing late-life reproductive output (c.f., [ 77]), the shifted reproductive schedules severely diminished relative fitness of worms in high-PQ treatments.
Part of an adaptive response to early life nutritional challenge might therefore be expected to be an acceleration in the age of reproductive maturation, provided that the organism can metabolically sustain earlier reproduction without further compromising its own viability.
These results are in accordance with the life-history theory that predicts stronger selection for early reproduction in conditions where mortality rate is high and late reproductive career less likely [28].
This pattern of early reproduction followed by senescence is all too familiar to us.
Marino Marini's figure of a horse benefited from its early reproduction by the German art historian Eduard Trier in 1954.
