Marmoset monkeys and humans are born with more plastic brains than other primates.

What is it about?

A big puzzle in the evolution of behavior is why human infants use caregiver feedback to learn how to produce proto-speech sounds while the infants of closely related primates like chimpanzees and macaque monkeys do not. In these species, vocalizations are seemingly fixed at birth. Recently, however, we learned that infants of a more distantly related species--the marmoset monkey--also learn one of their vocalizations like human infants: Their learning is helped by caregiver feedback. What do humans and marmoset monkeys share with each other but not with other primates, like chimps and macaques? Our study tests the hypothesis that humans and marmosets are born with more immature brains (and thus more plastic brains) than these other species. Our carefully analysis of neural developmental data supports our hypothesis.

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Why is it important?

Our findings is a great example of how changes in the timing of development--not just the advent of new brain structures or pathways--can help account for behavioral differences across species, even ones that are distantly related. It is also example how similar selection pressures can lead to similar solutions. All this is important not just for basic science but also when considering animal models for understanding human behavior and when it goes awry. In our view, marmoset monkeys are thus a great model for human infant vocal learning even though other primates might closer genetic relatives.