Fig. 1.

Vital rate statistics. Mean ± SD for (A) mortality μ_x and (B) fertility m_x, across 10 small-scale societies (solid lines, blue fill) and five wild chimpanzee populations (dashed lines, red fill). (C) CVs for survival CV(p_x) (dashed lines) and fertility CV(m_x) (solid lines) are calculated across humans (bold lines) and chimpanzees (thin lines). (D) Scaled covariance COV_sc(p_x, m_x) for humans (solid line, left y axis) and chimpanzees (dashed line, right y axis). The horizontal dotted line shows where COV_sc crosses zero.