Abstract
Despite being closely related, bonobos and chimpanzees show remarkable behavioral differences, the proximate origins of which remain unknown. This study examined the link between behavioral variation and variation in the vasopressin 1a receptor gene (Avpr1a) in bonobos. Chimpanzees are polymorphic for a ~360 bp deletion (DupB), which includes a microsatellite (RS3) in the 5′ promoter region of Avpr1a. In chimpanzees, the DupB deletion has been linked to lower sociability, lower social sensitivity, and higher anxiety. Chimpanzees and bonobos differ on these traits, leading some to believe that the absence of the DupB deletion in bonobos may be partly responsible for these differences, and to the prediction that similar associations between Avpr1a genotypes and personality traits should be present in bonobos. We identified bonobo personality dimensions using behavioral measures (SociabilityB, BoldnessB, OpennessB, ActivityB) and trait ratings (AssertivenessR, ConscientiousnessR, OpennessR, AgreeablenessR, AttentivenessR, ExtraversionR). In the present study we found that all 10 dimensions have nonzero heritabilities, indicating there is a genetic basis to personality, and that bonobos homozygous for shorter RS3 alleles were lower in AttentivenessR and higher in OpennessB. These results suggest that variations in Avpr1a genotypes explain both within and between species differences in personality traits of bonobos and chimpanzees.
Highlights
Despite being closely related, bonobos and chimpanzees show remarkable behavioral differences, the proximate origins of which remain unknown
A remaining challenge is to identify proximate mechanisms that underlie personality variation and ultimate mechanisms that explain how this variation is maintained in populations[3]
Models should incorporate explicit genetic mechanisms, since the expected response to natural selection of these traits depends on their genetic structure[9]
Summary
Bonobos and chimpanzees show remarkable behavioral differences, the proximate origins of which remain unknown. In the present study we found that all 10 dimensions have nonzero heritabilities, indicating there is a genetic basis to personality, and that bonobos homozygous for shorter RS3 alleles were lower in AttentivenessR and higher in OpennessB These results suggest that variations in Avpr1a genotypes explain both within and between species differences in personality traits of bonobos and chimpanzees. Whereas bonobos have three microsatellites (RS1, RS3 and STR1), the RS3 microsatellite is often missing in chimpanzees, as it is located in a ~360 bp region (DupB) that is deleted in a majority of chimpanzees[26,27] This deletion was associated with lower scores, primarily in male chimpanzees, in Sociability[28], and Friendliness and Smart[29], all personality traits derived from behavioral codings of affiliative behavior and/ or grooming. The DupB deletion was associated with a reduction in attentiveness to human social cues[31]
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