Table 1.

Generation intervals for each chimpanzee and gorilla study community

			Mean generation interval, y
Taxa	Study site	No. offspring	Female	CI	Male	CI	Both sexes	CI
Western chimpanzees	Taї-North	28	23.03	22.19–23.80	23.05	22.31–23.81	23.04	22.48–23.58
	Taї-Middle	4	31.71	28.34–35.15	26.06	23.90–28.32	28.89	26.80–31.03
	Taї-South	28	28.76	27.54–29.98	25.36	24.46–26.30	27.06	26.29–27.84
Eastern chimpanzees	Gombe-Kasekela	31	24.62	24.24–25.00	21.84	21.75–21.93	23.23	23.03–23.43
	Mahale-M	14	25.03	23.95–26.08	19.87	19.62–20.13	22.45	21.90–23.00
	Kibale-Ngogo	72	24.5	23.80–25.22	23.57	23.05–24.13	24.04	23.60–24.48
	Kibale-Kanyawara	15	23.34	22.43–24.25	28.42	27.15–29.75	25.88	25.04–26.68
	Budongo-Sonso	34	26.08	25.03–27.08	26.66	25.93–27.34	26.37	25.72–26.95
All chimpanzees		226	25.18	24.86–25.54	24.08	23.83–24.34	24.63	24.42–24.85
Mountain gorillas	Karisoke	97	18.18	17.97–18.37	20.27	20.23–20.30	19.22	19.12–19.32
	Bwindi	8	18.26	16.87–19.64	21.67	20.37–22.93	19.97	18.96–20.88
All gorillas		105	18.19	18.00–18.39	20.37	20.27–20.47	19.28	19.17–19.39
Humans*	Hunter–gatherers	157 societies	25.6		31.5		28.6
	Countries	360 societies	27.3		30.8		29.1

^*Fenner 2005 (22). Species-wide averages for chimpanzees and gorillas and human values are shown in bold type.