As he studies the neural mechanisms behind vocal learning, Jarvis is also pursuing a key question in evolutionary biology: Did the trait of vocal learning emerge independently in all six vocal-learning groups within the past 65 million years, as a now-dominant theory suggests? Or, did all vocal learners share a common ancestor with the trait, but then diverge as a result of subsequent, independent mass extinctions of vocal learning among various animals, including non-human primates? Though this question remains a mystery for now, Jarvis' latest work suggests that the evolution of vocal learning was accompanied by divergent, specialized expression of an ancient gene family in different vocal learning animals. Further, the diversity of expression seems to depend on the complexity of the animal's vocal syntax.
"Whether independent or dependent from a common ancestor, diversity of neurotransmitter receptors in their vocal systems is probably not an evolutionary cause of vocal learning, but a consequence of it, as diverse species-specific specializations can be assumed recent and ongoing evolution," Jarvis, Wada and colleagues wrote in their pending PNAS paper.
Moreover, they added: "With diverse specialization as a rule, it is not too far a stretch to suggest that vocal-learning mammals, including humans, also evolved diverse specialized glutamate receptor expression in vocal areas of their cerebrums and that these are related in part to vocal syntax complexity."
Jarvis received his doctoral degree from The Rockefeller University in 1995. He was one of 52 African American men out of more than 4,300 biologists to receive a Ph.D. in the United States that year. His own pathway to success was inspired by his