Animals are usually expected to avoid mating with relatives (kin avoidance) as incestuous mating can lead to the expression of inbreeding depression. Yet, theoretical models predict that unbiased mating with regards to kinship should be common, and that under some conditions, the inclusive fitness benefits associated with inbreeding can even lead to a preference for mating with kin. This mismatch between empirical and theoretical expectations generates uncertainty as to the prevalence of inbreeding avoidance in animals. Here, we synthesized 677 effect sizes from 139 experimental studies of mate choice for kin versus non-kin in diploid animals, representing 40 years of research, using a meta-analytical approach. Our meta-analysis revealed little support for the widely held view that animals avoid mating with kin, despite clear evidence of publication bias. Instead, unbiased mating with regards to kinship appears widespread across animals and experimental conditions. The significance of a variety of moderators was explored using meta-regressions, revealing that the degree of relatedness and prior experience with kin explained some variation in the effect sizes. Yet, we found no difference in kin avoidance between males and females, choice and no-choice experiments, mated and virgin animals or between humans and animals. Our findings highlight the need to rethink the widely held view that inbreeding avoidance is a given in experimental studies.

通常期望动物避免与亲属交配（回避亲属），因为乱伦交配会导致近亲繁殖抑郁症的表现。然而，理论模型预测，关于亲属关系的无偏见交配应该是普遍的，并且在某些情况下，与近亲繁殖相关的包容性健身益处甚至可以导致与亲属交配的偏好。经验和理论预期之间的这种不匹配导致动物近亲繁殖回避普遍存在的不确定性。在这里，我们使用荟萃分析方法，从 139 项二倍体动物亲属与非亲属的择偶实验研究中合成了 677 个效应值，代表了 40 年的研究。我们的荟萃分析显示，人们普遍认为动物避免与亲属交配的观点几乎没有得到支持，尽管有明显的发表偏倚证据。相反，关于亲属关系的无偏见交配似乎在动物和实验条件下普遍存在。使用元回归探讨了各种调节因素的重要性，揭示了与亲属的相关程度和先前经验解释了效应量的一些变化。然而，我们发现雄性和雌性之间的亲属回避、选择和非选择实验、交配动物和处女动物或人与动物之间没有差异。我们的研究结果强调需要重新思考人们广泛持有的观点，即实验研究中已经给出了避免近亲繁殖的观点。揭示了亲属关系的程度和先前的经验解释了影响大小的一些变化。然而，我们发现雄性和雌性之间的亲属回避、选择和非选择实验、交配动物和处女动物或人与动物之间没有差异。我们的研究结果强调需要重新思考人们广泛持有的观点，即实验研究中已经给出了避免近亲繁殖的观点。揭示了亲属关系的程度和先前的经验解释了影响大小的一些变化。然而，我们发现雄性和雌性之间的亲属回避、选择和非选择实验、交配动物和处女动物或人与动物之间没有差异。我们的研究结果强调需要重新思考人们广泛持有的观点，即实验研究中已经给出了避免近亲繁殖的观点。