Stanton Margaret A, Lonsdorf Elizabeth V, Pusey Anne E, Goodall Jane, Murray Carson M
Postdoctoral Scientist, Center for the Advanced Study of Hominid Paleobiology, George Washington University, 2110 G Street NW, Washington, DC 20052, U.S.A.
Assistant Professor of Psychology, Department of Psychology and Biological Foundations of Behavior Program, Franklin and Marshall College, P.O. Box 3003, Lancaster, PA 17604, U.S.A.
Curr Anthropol. 2014 Aug;55(4):483-489. doi: 10.1086/677053.
Parental investment theory predicts that maternal resources are finite and allocated among offspring based on factors including maternal age and condition, and offspring sex and parity. Among humans, firstborn children are often considered to have an advantage and receive greater investment than their younger siblings. However, conflicting evidence for this "firstborn advantage" between modern and hunter-gatherer societies raises questions about the evolutionary history of differential parental investment and birth order. In contrast to humans, most non-human primate firstborns belong to young, inexperienced mothers and exhibit higher mortality than laterborns. In this study, we investigated differences in maternal investment and offspring outcomes based on birth order (firstborn vs. later-born) among wild chimpanzees (). During the critical first year of life, primiparous mothers nursed, groomed, and played with their infants more than did multiparous mothers. Furthermore, this pattern of increased investment in firstborns appeared to be compensatory, as probability of survival did not differ by birth order. Our study did not find evidence for a firstborn advantage as observed in modern humans but does suggest that unlike many other primates, differences in maternal behavior help afford chimpanzee first-borns an equal chance of survival.
亲代投资理论预测，母体资源是有限的，并会根据包括母体年龄和状况、后代性别和胎次等因素在后代之间进行分配。在人类中，长子往往被认为具有优势，并且比他们的弟弟妹妹获得更多的投资。然而，现代社会和狩猎采集社会之间关于这种“长子优势”的相互矛盾的证据，引发了关于亲代投资差异和出生顺序进化历史的问题。与人类不同，大多数非人类灵长类动物的长子属于年轻、缺乏经验的母亲，并且死亡率比次子更高。在这项研究中，我们调查了野生黑猩猩中基于出生顺序（长子与次子）的母体投资和后代结果的差异。在生命的关键第一年，初产母亲比经产母亲更多地照顾、梳理和与婴儿玩耍。此外，这种对长子增加投资的模式似乎是一种补偿，因为生存概率在出生顺序上并无差异。我们的研究没有发现像现代人类中观察到的长子优势的证据，但确实表明，与许多其他灵长类动物不同，母体行为的差异有助于为黑猩猩长子提供平等的生存机会。
