Interspecies breeding has always happened, even among the ancients hominins. However, studying hominin hybrids is difficult, and scientists still struggle to determine whether hybridization was advantageous or disadvantageous to the offspring.
Now, a new one an investigation in Science found that this type of interbreeding actively selected against baboons in Africa, potentially signaling that the same was true among ancient hominins. Arising from a combination of field observations and genomic analyses, this discovery underscores the importance of studying other primates as models for human history, especially for aspects of human history that are impossible to observe in the present.
Ancient people tended to intermingle. In fact, Homo sapiens often mixed with similar types of Homo genus, including Neanderthals and other. This mixing is believed to have had a significant impact on human history and variation over time. However, scientists had previously hypothesized that this type of admixture would have been actively selected for by the processes of natural selection. The offspring of such pairs would be less likely to survive. But the passage of time and the extinction of all other hominins made this hypothesis particularly difficult to test.
One solution is to explore the other primates. In fact, scientists say interbreeding among today’s primate species, a selection of mammals including lemurs, lorises, monkeys and apes, in addition to humans, may shed light on interspecific interbreeding among ancient hominins.
Taking this comparative approach, one team of researchers analyzed the mating practices of baboons in the wild. Overall, their analysis showed that interspecific breeding actively selected against baboon populations, supporting the hypothesis that hominin hybrids do not have the same fitness for survival as their non-hybrid peers. More importantly, the researchers say, their analysis also highlights the value of other primates as surrogates for retrieving unavailable human history.
Baboon breeding study
To study interspecific breeding among other primates, the researchers turned to yellow baboons and anubis baboons around the Amboseli region of Kenya. There, they analyzed more than 50 years of field observations on the demography and dynamics of these populations, as well as genomic information from the progeny of the admixture.
Although field observations show that the offspring of this breeding are no less fit to survive, their genomic analysis seems to suggest otherwise. It showed that inbreeding selected in a manner similar to the hypothesis of admixture between humans and other hominins.
Ultimately, these findings could help scientists study human variation and history. But the researchers say the specifics of selection against hominin hybridization, including its mode and mechanics, are still murky and need further study.