A common belief among human life history researchers is that “harsher” environments – i.e., those with higher mortality rates and resource stress – select for “fast” life histories, i.e. earlier reproduction and faster senescence. In this study, I showed that these “harsh environments, fast life histories” – or HEFLH – hypotheses are poorly supported by evolutionary theory. The reason is that HEFLH hypotheses usually treat plastic responses to heterogeneous environmental conditions within a population, whereas the theory used to justify such hypotheses treat genetic responses to environmental changes across an entire population. Counter-intuitively, the predictions of the former do not generally apply to the latter: the optimal response to a harsh environment within a large heterogeneous environment is not necessarily the optimal strategy of a population uniformly inhabiting the same harsh environment.
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