The evolution of information donation: a targeted comparison between marmosets and squirrel monkeys

Abstract Proactive information donation is crucial for human cumulative cultural evolution. Evidence for proactive information donation in nonhuman animals is limited to a few examples, and its evolutionary origin remains debated. Here, we examine the role of cooperative breeding for the evolution of proactive information donation by comparing cooperatively breeding common marmosets and an independently breeding sister taxon, the squirrel monkeys, in a series of food sharing experiments. Food sharing was virtually absent in squirrel monkeys but highly prevalent in marmosets. Furthermore, experienced adult marmosets shared more food with immatures when food was more difficult than easy-to-access. This increase was mainly driven by the experienced adults, who proactively initiated sharing more often in the difficult condition, consistent with proactive information donation. These notable species differences have significant implications for the evolution of information donation in cooperatively breeding humans and its absence in other great apes who all breed independently.