People, especially people living as hunters and gatherers, have a much longer juvenile period than their closest relatives, the other hominoidea. We define juvenile period as the time from weaning to first reproduction. What might have been the selective pressures that led to its elongation? Over the years anthropologists have presented a variety of answers, ranging from the almost teleological "we are born undeveloped and mature slowly and remain dependent a long time so we can learn better", to the more reasoned - "advantages to later reproduction from continued growth (and learning) must outweigh the disadvantage of lost time". Several versions of these ideas assume that our hunting and gathering way of life requires much to be learned, and that much time must be spent on learning it. But is there any evidence?
Frank Marlowe and Nick Blurton Jones conducted experiments to test whether Hadza foragers who had lost several years of practice and experience were less effective at testable foraging skills. The results were surprising. There are alternative explanations for the length of the human juvenile period. The contest between theories about the juvenile period may one day teach us a lot about the evolution of human learning and the scheduling of development.
Some background information can be found in Blurton Jones et al. (1997) Why do Hadza children forage? In Segal, N.L., Weisfeld, G.E. and Weisfeld, C.C. (Eds.) Uniting Psychology and Biology: integratvie Perspectives on Human Development. APA, Washington DC.
Web page: http://www.gseis.ucla.edu/facpage/blurtonjones.html
Blurton Jones, NG (1997). Too good to be true? Is there really a trade-off between number and care of offspring in human reproduction? pp 83-86 in Betzig, L (ed.) Human Nature: a Critical Reader. Oxford University Press, New York.
Blurton Jones, NG, Hawkes, K, & O'Connell, JF. (1997). Why do Hadza children forage? In Segal, Nancy L, Weisfeld GE, & Weisfeld CC (eds.) Genetic, ethological and evolutionary Perspectives on Human Development. Essays in Honor of dr Daniel G Freedman. American Psychological Association. Washington DC.
Hawkes, K, O'Connell, JF and Blurton Jones, NG. 1995. Hadza children's foraging: juvenile dependency, social arrangements, and mobility among hunter-gatherers. Current Anthroppology 36: 688-700.
Blurton Jones, NG, Hawkes, K and Draper, P. (1994). Differences between Hadza and !Kung children's work: original affluence or practical reason? In E.S.Burch & Linda J Ellana (eds.) 1994. Key Issues in Hunter-Gatherer Research. Berg, Oxford.
Blurton Jones, N.G., K. Hawkes & P. Draper (1994). Foraging returns of !Kung adults and children: Why didn't !Kung children forage? J. Anthropological Research 50: 217 - 248.
Blurton Jones, NG. 1993 The lives of hunter - gatherer children. In M. Perreira & L. Fairbanks (eds) Juvenile Primates. Oxford University Press, Oxford and New York.
Blurton Jones, N.G. (1986). Bushman birth spacing: a test for optimal interbirth intervals. Ethology & Sociobiology 7: 91105.
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determined behaviour: Do bushman women maximise their reproductive success
by spacing births widely and foraging seldom? Pp 135158 in Human
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No 18. Ed. N. Blurton Jones & V. Reynolds. London: Taylor &