Synchrony Between Growth and Reproductive Patterns in Human Females: Early Investment in Growth Among Pume ´ Foragers Karen L. Kramer* and Russell D. Greaves Department of Anthropology, Harvard University, Cambridge, MA 02138 KEY WORDS life history; human growth; age at first birth; hunter-gatherers; South American Indians ABSTRACT Life history is an important framework for understanding many aspects of ontogeny and repro- duction relative to fitness outcomes. Because growth is a key influence on the timing of reproductive maturity and age at first birth is a critical demographic variable pre- dicting lifetime fertility, it raises questions about the syn- chrony of growth and reproductive strategies. Among the Pume ´, a group of South American foragers, young women give birth to their first child on average at age 15.5. Pre- vious research showed that this early age at first birth maximizes surviving fertility under conditions of high infant mortality. In this study we evaluate Pume ´ growth data to test the expectation that if early reproduction is advantageous, then girls should have a developmental trajectory that best prepares them for young childbearing. Analyses show that comparatively Pume ´ girls invest in skeletal growth early, enter puberty having achieved a greater proportion of adult body size and grow at low velocities during adolescence. For early reproducers grow- ing up in a food-limited environment, a precocious invest- ment in growth is advantageous because juveniles have no chance of pregnancy and it occurs before the onset of the competing metabolic demands of final reproductive maturation and childbearing. Documenting growth pat- terns under preindustrial energetic and demographic con- ditions expands the range of developmental variation not otherwise captured by normative growth standards and contributes to research on human phenotypic plasticity in diverse environments. Am J Phys Anthropol 141:235–244, 2010. V V C 2009 Wiley-Liss, Inc. Life history theory places central importance on rela- tionships between ontogeny, reproduction, and mortality (Kaplan et al., 2000; Hawkes and Paine, 2006). Relative to other mammals, primates generally and humans in particular grow for a long period of time before reaching reproductive age. But, within this general pattern, the pace of maturation varies considerably across human populations. While delayed childbearing is the norm for some populations, cross-cultural research indicates early reproduction is the best fitness option under conditions of high adult mortality (Geronimus et al., 1999; Geroni- mus, 2003; Migliano et al., 2007) and high infant mortal- ity (Kramer, 2008). Since growth is a key factor influenc- ing the timing of maturity and age of first birth is a strong predictor of lifetime fertility in natural fertility populations (Campbell and Wood, 1988; Bongaarts, 2002), variation in the relationship between growth patterns and reproductive strategies is an important domain of life history inquiry. The pace of maturation, growth completion, and age at first birth affects the length of a female’s reproductive span and potential lifetime reproductive success. The transition from growth to reproduction is a central life history tradeoff and is reflected in the physiology of growth completion, production of steroid hormones and activation of the reproductive axis. Menarche is cued to skeletal maturity and occurs after girls have accomplished 95% of their growth (Ellison, 1981, 2001). This growth pattern delays fecundity and prevents juveniles from conceiving until they are skele- tally mostly grown. Following menarche, girls achieve final adult stature growing slowly, at low velocities for several years. Gonadal estrogen, which promotes ovarian cycling, also is critical to the process of long bone miner- alization, regulating epiphyseal fusion, and growth ter- mination (Nilsson et al., 1994; Schwartz et al., 1995). In preparation for reproduction, and after the mechanical constraints of stature and pelvic size are solved, surplus energy is diverted into weight gain, fat storage, and fe- cundity (Ellison, 2001). While certain aspects of this pro- cess are canalized and the timing of body size maturity is variable. Growth standards provide germane data on human growth expectations. However, these expectations about growth norms and variation are derived prima- rily from anthropometric surveys among industrialized Grant sponsor: National Science Foundation; Grant number: 0349963; Grant sponsor: NSF; Grant number: DBS-9123875; Grant sponsor: L.S.B. Leakey Foundation. *Correspondence to: Karen L. Kramer, Department of Anthropol- ogy, Harvard University, Peabody Museum, 11 Divinity Ave., Cam- bridge, MA 02138. E-mail: kkramer@fas.harvard.edu Received 22 December 2008; accepted 12 June 2009 DOI 10.1002/ajpa.21139 Published online 20 October 2009 in Wiley InterScience (www.interscience.wiley.com). V V C 2009 WILEY-LISS, INC. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 141:235–244 (2010)