Brent Lauren J N, Franks Daniel W, Foster Emma A, Balcomb Kenneth C, Cant Michael A, Croft Darren P
Centre for Research in Animal Behaviour, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QG, UK.
Department of Biology and Department of Computer Science, University of York, York YO10 5DD, UK.
Curr Biol. 2015 Mar 16;25(6):746-750. doi: 10.1016/j.cub.2015.01.037. Epub 2015 Mar 5.
Classic life-history theory predicts that menopause should not occur because there should be no selection for survival after the cessation of reproduction [1]. Yet, human females routinely live 30 years after they have stopped reproducing [2]. Only two other species-killer whales (Orcinus orca) and short-finned pilot whales (Globicephala macrorhynchus) [3, 4]-have comparable postreproductive lifespans. In theory, menopause can evolve via inclusive fitness benefits [5, 6], but the mechanisms by which postreproductive females help their kin remain enigmatic. One hypothesis is that postreproductive females act as repositories of ecological knowledge and thereby buffer kin against environmental hardships [7, 8]. We provide the first test of this hypothesis using a unique long-term dataset on wild resident killer whales. We show three key results. First, postreproductively aged females lead groups during collective movement in salmon foraging grounds. Second, leadership by postreproductively aged females is especially prominent in difficult years when salmon abundance is low. This finding is critical because salmon abundance drives both mortality and reproductive success in resident killer whales [9, 10]. Third, females are more likely to lead their sons than they are to lead their daughters, supporting predictions of recent models [5] of the evolution of menopause based on kinship dynamics. Our results show that postreproductive females may boost the fitness of kin through the transfer of ecological knowledge. The value gained from the wisdom of elders can help explain why female resident killer whales and humans continue to live long after they have stopped reproducing.
经典的生命史理论预测，更年期不应出现，因为在生殖停止后不应存在对生存的选择压力[1]。然而，人类女性在停止生育后通常还能活30年[2]。只有另外两个物种——虎鲸（Orcinus orca）和短鳍领航鲸（Globicephala macrorhynchus）[3, 4]——具有类似的生殖后寿命。理论上，更年期可以通过广义适合度优势进化而来[5, 6]，但生殖后女性帮助其亲属的机制仍然是个谜。一种假设是，生殖后女性充当生态知识的储存库，从而保护亲属免受环境困难的影响[7, 8]。我们利用关于野生定居虎鲸的独特长期数据集首次对这一假设进行了检验。我们展示了三个关键结果。第一，生殖后老龄雌性在鲑鱼觅食地集体行动时带领群体。第二，在鲑鱼数量少的困难年份，生殖后老龄雌性的领导作用尤为突出。这一发现至关重要，因为鲑鱼数量驱动着定居虎鲸的死亡率和繁殖成功率[9, 10]。第三，雌性更有可能带领儿子而非女儿，这支持了基于亲属关系动态的更年期进化最新模型[5]的预测。我们的结果表明，生殖后女性可能通过生态知识的传递提高亲属的适合度。从年长者智慧中获得的价值有助于解释为什么雌性定居虎鲸和人类在停止生育后仍能长寿。
