Data from: Parent-offspring facial resemblance increases with age in rhesus macaques

Kin recognition is a key ability which facilitates the acquisition of inclusive fitness benefits and enables optimal outbreeding. In primates, phenotype matching is considered particularly important for the recognition of patrilineal relatives, as information on paternity is unlikely to be available via social familiarity. Phenotypic cues to both paternal and maternal relatedness exist in the facial features of humans and other primates. However, theoretical models suggest that in systems with parentage uncertainty it may be adaptive for offspring to conceal such cues when young, in order to avoid potential costs of being discriminated against by unrelated adults. Using experienced human raters, we demonstrate in a computer-based task that detection of parent-offspring resemblances in the faces of rhesus macaques (Macaca mulatta) increases significantly with offspring age. Moreover, this effect is specific to information about kinship, as raters were extremely successful at discriminating individuals even amongst the youngest animals. To our knowledge, this is the first evidence in non-humans for the age-dependent expression of visual cues used in kin recognition.亲缘识别是一项核心能力，既能帮助个体获取广义适合度（inclusive fitness）收益，又可助力实现最优远交。在灵长类动物中，表型匹配（phenotype matching）被认为对父系亲属的识别尤为关键，因为通过社交熟悉度无法获取父权相关信息。人类与其他灵长类的面部特征中，均存在可反映父系与母系亲缘关系的表型线索。不过，理论模型显示，在亲权不确定性的社会系统中，幼崽若在幼年时隐藏这类表型线索或许具备适应性优势，以此规避被无亲缘关系的成年个体歧视所带来的潜在代价。本研究借助经过训练的人类评分者，通过计算机任务证实：恒河猴（Macaca mulatta）面部所呈现的亲子相似性辨识度，会随幼崽年龄增长而显著提升。此外，该效应仅针对亲缘关系相关信息——因为评分者即便在最年幼的恒河猴个体中，也能出色完成个体区分任务。据我们所知，本研究首次在非人类物种中证实了亲缘识别所依赖的视觉线索存在年龄依赖性表达。