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.亲属识别是一项核心能力，可帮助个体获得广义适合度（inclusive fitness）收益，并实现最优远交繁殖。在灵长类动物中，表型匹配（phenotype matching）被认为对父系亲属识别尤为关键，因为通过社交熟悉度无法获取父权相关信息。人类及其他灵长类的面部特征中，存在可反映父系与母系亲缘关系的表型线索。不过，理论模型表明，在亲子关系存在不确定性的种群中，幼崽在年幼时隐藏此类表型线索可能具有适应性优势，以规避被无亲缘关系的成年个体歧视所带来的潜在成本。本研究借助经过训练的人类评分者，通过计算机任务证实：随着恒河猴（Macaca mulatta）幼崽年龄增长，人类评分者识别其面部亲子相似性的准确率显著提升。此外，该效应仅针对亲缘识别相关信息——即便在最年幼的个体组中，评分者仍能精准区分不同个体，证明了这一效应的特异性。据我们所知，这是首次在非人类物种中发现，亲属识别所依赖的视觉表型线索的表达会随年龄变化的相关证据。