Elephants as an animal model for self-domestication

Abstract

Humans are unique in their sophisticated culture and societal structures, their complex languages, and their extensive tool use. According to the human self-domestication hypothesis, this unique set of traits may be the result of an evolutionary process of self-induced domestication, in which humans evolved to be less aggressive and more cooperative. However, the only other species that has been argued to be self-domesticated besides humans so far is bonobos, resulting in a narrow scope for investigating this theory limited to the primate order. Here, we propose an animal model for studying self-domestication: the elephant. First, we support our hypothesis with an extensive cross-species comparison, which suggests that elephants indeed exhibit many of the features associated with self-domestication (e.g., reduced aggression, increased prosociality, extended juvenile period, increased playfulness, socially regulated cortisol levels, and complex vocal behavior). Next, we present genetic evidence to reinforce our proposal, showing that genes positively selected in elephants are enriched in pathways associated with domestication traits and include several candidate genes previously associated with domestication. We also discuss several explanations for what may have triggered a self-domestication process in the elephant lineage. Our findings support the idea that elephants, like humans and bonobos, may be self-domesticated. Since the most recent common ancestor of humans and elephants is likely the most recent common ancestor of all placental mammals, our findings have important implications for convergent evolution beyond the primate taxa, and constitute an important advance toward understanding how and why self-domestication shaped humans’ unique cultural niche.

Rapid evolution of genes with anti-cancer functions during the origins of large bodies and cancer resistance in elephants

“…We previously reported the results of a preliminary selection scan using the same dataset of alignments used here and the base ABSREL model, which did not include synonymous rate variation or multiple hits (Raviv et al, 2023). We identified 674 positively selected genes enriched in several Panther pathways (Mi et al, 2013; Mi and Thomas, 2009; Thomas et al, 2022) related to neurotransmitter signaling (Raviv et al, 2023).…”

“…We previously reported the results of a preliminary selection scan using the same dataset of alignments used here and the base ABSREL model, which did not include synonymous rate variation or multiple hits (Raviv et al, 2023). We identified 674 positively selected genes enriched in several Panther pathways (Mi et al, 2013; Mi and Thomas, 2009; Thomas et al, 2022) related to neurotransmitter signaling (Raviv et al, 2023). However, we found in this study that synonymous rate variation across sites improved model fit for all genes, suggesting that at least some of the 674 genes we previously reported as positively selected may be false positives; indeed, only 215 (31.9%) were inferred as positively selected by ABSREL[S].…”

Toward an evolutionary account of the changes in the human pitch vocal system

“…In turn, this is expected to have resulted in a constellation of body, cognitive, and behavioral changes in humans that parallel domestication features in other species. In fact, the external factors that seemingly favored prosocial behaviors in humans can be expected to trigger self-domestication features in any species, as observed in bonobos (Hare et al, 2012 ) or elephants (Raviv et al, 2023 ). In the case of humans, the traits resulting from our self-domestication include modifications in the skull and the facial area that have been characterized as an increased “feminization” of inherited hominin features.…”

Flame-forged divergence? Ancient human fires and the evolution of diurnal and nocturnal lineages in Mediterranean geckos

“…Whereas these “domestication” events are generally recognized as the product of planned actions, aimed to annex useful plant and animal species into the anthropic niche, some organisms established synanthropic relationships beyond the human intention. These latter occurrences are noticeable in many evolutionary processes as the self-domestication developed in mice and rats (Pocock et al 2004), sparrows (Ravinet et al 2018), cockroaches (Booth et al 2011), foxes (Parsons et al 2020), and elephants (Raviv et al 2023).…”