School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85281, USA; Institute for Human Origins, Arizona State University, Tempe, AZ 85281, USA.
Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig 04103, Germany.
Curr Biol. 2020 May 4;30(9):1716-1720.e3. doi: 10.1016/j.cub.2020.02.013. Epub 2020 Mar 12.
In polygynous and polygynandrous species, there is often intense male-male competition over access to females, high male reproductive skew, and more male investment in mating effort than parenting effort [1]. However, the benefits derived from mating effort and parenting effort may change over the course of males' lives. In many mammalian species, there is a ∩-shaped relationship between age, condition, and resource holding power as middle-aged males that are in prime physical condition outcompete older males [2-8] and sire more infants [9-12]. Thus, males might derive more benefits from parenting effort than mating effort as they age and their competitive abilities decline [13]. Alternatively, older males may invest more effort in making themselves attractive to females as mates [14]. One way that older males might do so is by developing relationships with females and providing care for their offspring [14, 15]. Savannah baboons provide an excellent opportunity to test these hypotheses. They form stable multi-male, multi-female groups, and males compete for high ranking positions. In yellow and chacma baboons (Papio cynocephalus and P. ursinus), there is a ∩-shaped relationship between male age and dominance rank [12], and high rank enhances paternity success [12, 16]. Lactating female baboons form close ties ("primary associations" hereafter) with particular males [15-20], who support them and their infants in conflicts [15, 19] and buffer their infants from rough handling [20]. Females' primary associates are often, but not always, the sires of their current infants [16, 20-22].
在多配偶制和多夫制物种中，雄性之间常常存在着激烈的竞争，以争夺与雌性的接触机会，雄性的生殖能力存在高度偏斜，雄性在交配努力上的投入多于在育儿努力上的投入[1]。然而，从交配努力和育儿努力中获得的好处可能会随着雄性寿命的变化而变化。在许多哺乳动物物种中，年龄、状况和资源持有能力之间存在一个∩形关系，中年雄性处于最佳身体状况，能够胜过老年雄性[2-8]，并生育更多的婴儿[9-12]。因此，随着年龄的增长和竞争能力的下降，雄性可能会从育儿努力中获得更多的好处，而不是从交配努力中获得更多的好处[13]。或者，老年雄性可能会投入更多的精力来使自己对雌性有吸引力，成为伴侣[14]。老年雄性可能会通过与雌性建立关系并为其后代提供照顾来实现这一点[14, 15]。萨凡纳狒狒为检验这些假设提供了一个极好的机会。它们形成稳定的多雄性、多雌性群体，雄性竞争高排名。在黄狒狒和山魈（Papio cynocephalus 和 P. ursinus）中，雄性年龄和支配地位之间存在∩形关系[12]，高地位可提高父权成功[12, 16]。哺乳期的雌性狒狒与特定的雄性形成紧密的联系（以下简称“主要关联”）[15-20]，雄性会在冲突中支持它们和它们的婴儿[15, 19]，并缓冲它们的婴儿免受粗暴对待[20]。雌性的主要伴侣通常是（但并不总是）其当前婴儿的父亲[16, 20-22]。
