The emergence of emotionally modern humans: implications for language and learning.

According to the Cooperative Breeding Hypothesis, apes with the life-history attributes of those in the line leading to the genus Homo could not have evolved unless male and female allomothers had begun to help mothers care for and provision offspring. As proposed elsewhere, the unusual way hominins reared their young generated novel phenotypes subsequently subjected to Darwinian social selection favouring those young apes best at monitoring the intentions, mental states and preferences of others and most motivated to attract and appeal to caretakers. Not only were youngsters acquiring information in social contexts different from those of other apes, but they would also have been emotionally and neurophysiologically different from them in ways that are relevant to how humans learn. Contingently delivered rewards to dependents who attracted and ingratiated themselves with allomothers shaped their behaviours and vocalizations and transformed the way developing youngsters learned from others and internalized their preferences. This article is part of the theme issue 'Life history and learning: how childhood, caregiving and old age shape cognition and culture in humans and other animals'.

Secondary sex ratios by maternal rank, parity, and age in captive rhesus macaques (Macaca mulatta).

Analysis of 645 conceptions by captive rhesus macaques (Macaca mulatta) with known reproductive histories indicated that maternal age and parity had little effect on the sex of progeny. There was, however, a slight indication that high-ranking females produced a higher proportion of daughters and relatively fewer sons than did low-ranking females. These results provide only weak support for the "advantaged daughter" hypothesis suggested by three previous studies of cercopithecine monkeys, and therefore they further confound the conflicting results for macaques and baboons in general.