How to explain the unusually late age at skill competence among humans

Abstract

Humans stand out among primates and other mammals in reaching adult-level foraging skills very late in development, well after the onset of reproduction. The aim of this paper is to place this unusual human skill development into a broader comparative context. Among birds and mammals in general, duration of immaturity, indexed by age at first reproduction (AFR), and adult brain size have undergone correlated evolution. This pattern is consistent with two causal processes: AFR is either limited by the time needed to learn adult-level skills (needing to learn) or by the energy needed to grow brain and body to full size (energetic constraints). We tested predictions arising from these two hypotheses with data retrieved from the published literature for 57 mammal and bird species. First, most mammals reach adult-level foraging skills well before the developmental period is completed, implying that energy constraints determine the age at first reproduction, whereas most birds reach adult-level foraging skills around the time of maturity, suggesting time needed for skill acquisition determines the onset of reproduction. Second, within mammals we found that with increasing niche complexity, the age of adult-level skill competence moves closer to the age at first reproduction. Third, when looking at how adult-level skills can be reached later, we found that gregariousness, slow conservative development and post-weaning provisioning allow mammals to reach their skills later. Finally, in species with intense sharing of resources (such as cooperative hunters) competence in foraging skills may even reach peak values after age of first reproduction. We conclude that the human pattern of skill acquisition could arise because our hominin ancestors added cooperative breeding and hunting to the slow development they had as great apes with increasingly complex niches. This result provides a broad biological foundation for the embodied capital model.

Old stones' song: Use-wear experiments and analysis of the Oldowan quartz and quartzite assemblage from Kanjera South (Kenya)

“…Skill-based acquisition of foods that could be shared within a group, and be used to provision subadults who were unlikely to meet their own nutritional needs, may thus have been an important component of hominin socioecology at Kanjera South (Oliver, 1994;Kaplan et al, 2000;Aiello & Key, 2002;Schuppli et al, 2012;Swedell & Plummer, 2012;Crittenden et al, 2013). 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Finally, while it is possible that the use-wear derives from activities that were carried out "on-site," or in the immediate vicinity of the Kanjera South locality, quartzite and possibly quartz were transported over 10 km to the site.…”

If at first you don't succeed… Studies of ontogeny shed light on the cognitive demands of habitual tool use

“…A preliminary comparison of other routine or non-tool users and habitual tool users also suggests a relative late age at skill competence for habitual tool users (figure 1). Sea otters appear to be an outlier among the habitual tool users in acquiring tool competence relatively fast; whereas spotted hyaenas and wolves appear to be outliers among the non-routine tool users because they acquire their skills 1 Not much known yet on individual variation or skill acquisition (but see [18,20] [55]). What are immatures doing during this period?…”

The reluctant innovator: orangutans and the phylogeny of creativity

“…A developmental approach is essential because innovations are by definition behaviours that do not have a strong genetic basis and thus do not arise reliably during development, but must instead be acquired and may therefore accumulate with age. We have done extensive studies of skill development in wild orangutans [24]. The data yield the paradoxical result that wild orangutans are novelty averse, rarely engage in independent exploration, and yet have extensive repertoires of learned skills, which qualify as innovations, which they acquire mostly through socially induced exploration.…”