Center for the Advanced Study of Human Paleobiology, Department of Anthropology, George Washington University, Washington, District of Columbia.
Department of Psychology, Franklin and Marshall College, Lancaster, Pennsylvania.
Am J Phys Anthropol. 2020 Jan;171(1):100-109. doi: 10.1002/ajpa.23935. Epub 2019 Oct 6.
Primates exhibit variation in rates of growth and development. Variation in female growth and development across ape species appears to be explained by the Ecological Risk Aversion Hypothesis (ERAH). Indeed, existing data on variation in somatic growth and reproductive maturation between humans' closest living ape relatives, bonobos and chimpanzees, appear to be consistent with this hypothesis. However, existing data on behavioral maturation between the two species appear to contradict this hypothesis. We present novel behavioral data on infant and juvenile females from wild populations of both species in order to further evaluate predictions of the ERAH as it relates to the speed of behavioral maturation.
We analyzed 3 years of behavioral data on 17 female bonobos (<8 years of age) from LuiKotale, Democratic Republic of the Congo and 40 years of behavioral data on 30 age-matched female chimpanzees from Gombe, Tanzania. We compared the timing of (a) the attainment of independence from mothers and (b) the development of social skills using the following proxies: proximity between females and their mothers and the time that females spent engaged in eating, suckling, social play, social grooming, and riding on their mothers.
We did not find species differences in the proportion of time that females spent in contact with their mothers or engaged in eating, suckling, social play, or social grooming. Female bonobos spent more time riding on their mothers than did female chimpanzees. Female bonobos spent more time at distances greater than 5 m from their mothers during the ages of 3-8 years, but females did not differ during the ages of 0-3 years.
Behavioral maturation is largely similar between females of the two species based on the ages and proxies considered herein. We propose alternative explanations for the differences that we found in proximity and riding that do not invoke differences in underlying rates of maturation.
灵长类动物的生长和发育速度存在差异。在类人猿物种中，雌性的生长和发育差异似乎可以用生态风险规避假说（ERAH）来解释。事实上，现有的关于人类最亲近的猿类亲属——倭黑猩猩和黑猩猩之间的体生长和生殖成熟的变异性的数据似乎与这一假说一致。然而，关于这两个物种之间行为成熟的现有数据似乎与这一假说相矛盾。我们提出了关于这两个物种的野生种群中幼雌和未成年雌的新的行为数据，以进一步评估 ERAH 对行为成熟速度的预测。
我们分析了来自刚果民主共和国的 LuiKotale 的 17 只雌性倭黑猩猩（<8 岁）的 3 年行为数据和来自坦桑尼亚的 Gombe 的 30 只年龄匹配的雌性黑猩猩的 40 年行为数据。我们比较了以下两种方法的时间：（a）女性从母亲那里获得独立的时间；（b）发展社会技能的时间，使用的代理指标是：女性与母亲的距离和女性在进食、哺乳、社交游戏、社交梳理和骑在母亲身上的时间。
我们没有发现两种物种的雌性在与母亲接触或进食、哺乳、社交游戏或社交梳理方面的时间比例有差异。雌性倭黑猩猩比雌性黑猩猩花更多的时间骑在母亲身上。雌性倭黑猩猩在 3-8 岁时与母亲的距离大于 5 米的时间较多，但在 0-3 岁时则没有差异。
根据本文所考虑的年龄和代理指标，两种物种的雌性的行为成熟度基本相似。我们提出了替代解释，以解释我们在接近度和骑行方面发现的差异，而不考虑成熟速度的差异。
