OK, this doesn't have to do with travelling at all, but I found it interesting:
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Lonnie W. Aarssen (2007)
Some bold evolutionary predictions for the future of mating in humans
Oikos 116 (10), 1768–1778.
doi:10.1111/j.2007.0030-1299.16170.x

Why are many human populations presently ‘imploding’ with below-replacement fertility? Why are more and more young adults in these societies choosing to remain single and/or childless? Based on first principles of evolutionary theory, predictions can be derived for changes over time in the relative frequency distributions of four traits in humans proposed as the most direct determinants of the propensity to mate and reproduce: attractions to sex, legacy, leisure and parenting. In the past, high fitness was most profoundly determined by strong sex drive and strong legacy drive, especially in males. Female fertility was largely controlled by dominant males, who were then free to engage in attractions to both leisure and legacy through ‘memes’ (as well as through genes, or offspring) without any penalty on fitness. Natural selection in the past, therefore, neither strongly favoured nor strongly disfavoured any particular intrinsic female inclinations or preferences that might affect offspring production. The recent, widespread, and continuing rise in the empowerment of women, however, defines a dramatically different contemporary selection regime, where women are now free to indulge in their evolved attractions to leisure and legacy through memes inherited from predecessors, both of which represent compelling distractions from parenthood. The implications for the future survival of marriage and parenthood as cultural institutions look dismal in the short term, but promising in the long term.
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Will humans go extinct? Will there be a female-dominated society where the males are just appendages, as in anglerfish? Stay tuned...