Abstract
According to life-history theory, any organism that maximizes fitness will face a trade-off between female fertility and offspring survivorship. This trade-off has been demonstrated in a variety of species, but explicit tests in humans have found a positive linear relationship between fitness and fertility. The failure to demonstrate a maximum beyond which additional births cease to enhance fitness is potentially at odds with the view that human fertility behaviour is currently adaptive. Here we report, to our knowledge, the first clear evidence for the predicted nonlinear relationship between female fertility and reproductive success in a human population, the Dogon of Mali, West Africa. The predicted maximum reproductive success of 4.1+/-0.3 surviving offspring was attained at a fertility of 10.5 births. Eighty-three per cent of the women achieved a lifetime fertility level (7-13 births) for which the predicted mean reproductive success was within the confidence limits (3.4 to 4.8) for reproductive success at the optimal fertility level. Child mortality, rather than fertility, was the primary determinant of fitness. Since the Dogon people are farmers, our results do not support the assumptions that: (i) contemporary foragers behave more adaptively than agriculturalists, and (ii) that adaptive fertility behaviour ceased with the Neolithic revolution some 9000 years ago. We also present a new method that avoids common biases in measures of reproductive success.
Full Text
The Full Text of this article is available as a PDF (153.6 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Borgerhoff Mulder M Optimizing offspring: the quantity-quality tradeoff in agropastoral Kipsigis. Evol Hum Behav. 2000 Nov;21(6):391–410. doi: 10.1016/s1090-5138(00)00054-4. [DOI] [PubMed] [Google Scholar]
- Caldwell J. C., Caldwell P. The demographic evidence for the incidence and cause of abnormally low fertility in tropical Africa. World Health Stat Q. 1983;36(1):2–34. [PubMed] [Google Scholar]
- Harpending H. Infertility and forager demography. Am J Phys Anthropol. 1994 Mar;93(3):385–397. doi: 10.1002/ajpa.1330930310. [DOI] [PubMed] [Google Scholar]
- Hill K., Kaplan H. Life history traits in humans: theory and empiricial studies. Annu Rev Anthropol. 1999;28:397–430. doi: 10.1146/annurev.anthro.28.1.397. [DOI] [PubMed] [Google Scholar]
- Menozzi P., Piazza A., Cavalli-Sforza L. Synthetic maps of human gene frequencies in Europeans. Science. 1978 Sep 1;201(4358):786–792. doi: 10.1126/science.356262. [DOI] [PubMed] [Google Scholar]
- Pennington R., Harpending H. Fitness and fertility among Kalahari !Kung. Am J Phys Anthropol. 1988 Nov;77(3):303–319. doi: 10.1002/ajpa.1330770304. [DOI] [PubMed] [Google Scholar]
- Perez A., Vela P., Masnick G. S., Potter R. G. First ovulation after childbirth: the effect of breast-feeding. Am J Obstet Gynecol. 1972 Dec 15;114(8):1041–1047. doi: 10.1016/0002-9378(72)90866-6. [DOI] [PubMed] [Google Scholar]
- Sokal R. R., Oden N. L., Wilson C. Genetic evidence for the spread of agriculture in Europe by demic diffusion. Nature. 1991 May 9;351(6322):143–145. doi: 10.1038/351143a0. [DOI] [PubMed] [Google Scholar]
- Strassmann B. I., Warner J. H. Predictors of fecundability and conception waits among the Dogon of Mali. Am J Phys Anthropol. 1998 Feb;105(2):167–184. doi: 10.1002/(SICI)1096-8644(199802)105:2<167::AID-AJPA5>3.0.CO;2-S. [DOI] [PubMed] [Google Scholar]