Primate Growth in the Slow Lane: A Study of Inter-Species Variation in the Growth Constant A

Primates grow and develop slowly for mammalian standards. Charnov showed that primates grow at only about 40% of the rates observed in other mammals of similar size. However, previous estimates of growth rates in primates were derived from regressions of adult body weight on age at first reproduction in different species, and therefore represent only an average trend for primates. Based on Charnov's 'growth law', we estimated the growth constant A directly from published growth curves for 36 primate species from strepsirrhines to apes. We show that although primate growth is slow in all sampled species in comparison with the mammalian average, there is significant variation around the primate mean. Lemurids are particularly interesting due to their wide range of A values, and further study is required to determine whether environmental unpredictability could lead to the evolution of both very fast and very slow grow in different species. Results also indicate significant negative correlations between the growth constant A and both age at first reproduction and duration of the juvenile period, lending support to the juvenile risk hypothesis.