Lahdenperä M, Russell A F, Lummaa V
Section of Ecology, Department of Biology, University of Turku, 20014, Turku, Finland.
Proc Biol Sci. 2007 Oct 7;274(1624):2437-44. doi: 10.1098/rspb.2007.0688.
Life-history theory suggests that individuals should live until their reproductive potential declines, and the lifespan of human men is consistent with this idea. However, because women can live long after menopause and this prolonged post-reproductive life can be explained, in part, by the fitness enhancing effects of grandmothering, an alternative hypothesis is that male lifespan is influenced by the potential to gain fitness through grandfathering. Here we investigate whether men, who could not gain fitness through reproduction after their wife's menopause (i.e. married only once), enhanced their fitness through grandfathering in historical Finns. Father presence was associated with reductions in offspring age at first reproduction and birth intervals, but generally not increases in reproductive tenure lengths. Father presence had little influence on offspring lifetime fecundity and no influence on offspring lifetime reproductive success. Overall, in contrast to our results for women in the same population, men do not gain extra fitness (i.e. more grandchildren) through grandfathering. Our results suggest that if evidence for a 'grandfather' hypothesis is lacking in a monogamous society, then its general importance in shaping male lifespan during our more promiscuous evolutionary past is likely to be negligible.
生活史理论表明，个体应活到其生殖潜力下降之时，人类男性的寿命与这一观点相符。然而，由于女性在绝经后仍能存活很长时间，且这种延长的生殖后生活在一定程度上可以通过祖母角色对适应性的增强作用来解释，另一种假说是男性的寿命受通过祖父角色获得适应性的潜力影响。在此，我们研究在历史上的芬兰人中，那些在妻子绝经后无法通过生育获得适应性的男性（即只结过一次婚）是否通过祖父角色提高了他们的适应性。父亲的存在与后代首次生育年龄的降低和生育间隔有关，但一般与生殖期长度的增加无关。父亲的存在对后代一生的生育力影响很小，对后代一生的生殖成功没有影响。总体而言，与我们对同一人群中女性的研究结果相反，男性不会通过祖父角色获得额外的适应性（即更多的孙辈）。我们的结果表明，如果在一夫一妻制社会中缺乏“祖父”假说的证据，那么在我们更为滥交的进化过去，它在塑造男性寿命方面的普遍重要性可能微不足道。
