Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK.
Proc Biol Sci. 2013 Sep 7;280(1766):20131343. doi: 10.1098/rspb.2013.1343.
Many studies in humans have shown that adverse experience in early life is associated with accelerated reproductive timing, and there is comparative evidence for similar effects in other animals. There are two different classes of adaptive explanation for associations between early-life adversity and accelerated reproduction, both based on the idea of predictive adaptive responses (PARs). According to external PAR hypotheses, early-life adversity provides a 'weather forecast' of the environmental conditions into which the individual will mature, and it is adaptive for the individual to develop an appropriate phenotype for this anticipated environment. In internal PAR hypotheses, early-life adversity has a lasting negative impact on the individual's somatic state, such that her health is likely to fail more rapidly as she gets older, and there is an advantage to adjusting her reproductive schedule accordingly. We use a model of fluctuating environments to derive evolveability conditions for acceleration of reproductive timing in response to early-life adversity in a long-lived organism. For acceleration to evolve via the external PAR process, early-life cues must have a high degree of validity and the level of annual autocorrelation in the individual's environment must be almost perfect. For acceleration to evolve via the internal PAR process requires that early-life experience must determine a significant fraction of the variance in survival prospects in adulthood. The two processes are not mutually exclusive, and mechanisms for calibrating reproductive timing on the basis of early experience could evolve through a combination of the predictive value of early-life adversity for the later environment and its negative impact on somatic state.
许多人类研究表明，早期生活中的逆境经历与生殖时机的加速有关，其他动物也有类似影响的比较证据。对于早期逆境经历与生殖加速之间的关联，有两种不同的适应性解释，都基于预测性适应反应（PAR）的概念。根据外部 PAR 假说，早期逆境经历为个体将要进入的环境条件提供了“天气预报”，个体为适应这种预期环境而发展出适当的表型是适应性的。在内部 PAR 假说中，早期逆境经历对个体的体状态产生持久的负面影响，因此随着年龄的增长，她的健康状况更有可能迅速恶化，相应地调整生殖计划会有优势。我们使用波动环境模型，推导出在长寿生物体中，对早期逆境经历反应的生殖时机加速的可进化性条件。通过外部 PAR 过程进行加速进化，早期线索必须具有高度的有效性，个体环境的年自相关水平必须几乎完美。通过内部 PAR 过程进行加速进化需要早期经历必须决定成年后生存前景的很大一部分方差。这两个过程并非互斥，基于早期经验校准生殖时机的机制可能通过早期逆境经历对后期环境的预测价值及其对体状态的负面影响的结合而进化。
