Developmental delays may explain differences in behavior of ape species

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Washington, January 29 (ANI): A new research has suggested that developmental delay may explain major differences in the physical appearance, behavior, and cognition in two different species of apes.

The research suggests that evolutionary changes in cognitive development underlie the extensive social and behavioral differences that exist between chimpanzees and bonobos, two closely related species of great apes.

Although chimpanzees and bonobos have a very close genetic relationship with each other, the two species display major differences in their physical appearance, behavior, and cognition.

For example, when compared to chimpanzees, bonobos seem to be much more peaceful and easygoing, retaining juvenile levels of play as adults, exhibiting low levels of aggression towards one another, and being much more likely than adult chimpanzees to share resources.

It has been suggested that these differences might be a result of species-specific shifts in the developmental pathways that link infancy with adulthood.

"Thus far, there has been no direct test of the hypothesis that certain aspects of behavior or cognition in adult bonobos represent developmentally delayed forms of the traits found in chimpanzees," explained Victoria Wobber of the Department of Human Evolutionary Biology at Harvard University, the lead study author.

"We tested this hypothesis by comparing skills of semi-free-ranging infant, juvenile, and adult bonobos and chimpanzees in three feeding competition tasks, given the prediction that this area in particular differs between the two species," she said.

Wobber and colleagues observed that as chimpanzees reached adulthood, they became more and more intolerant of sharing food, whereas bonobos retained juvenile levels of food-related tolerance.

Furthermore, chimpanzees consistently outperformed bonobos of the same age in tests where the subjects had to figure out which experimenters held a food reward.

"Bonobos took longer to develop the same skill level shown even among the youngest of the chimpanzees that were tested," said Wobber.

"It seemed as if adult chimpanzees were able to exhibit more social restraint than adult bonobos," she added.

The findings support the hypothesis that developmental delays play a role in shaping differences in the social psychology and behavior of chimpanzees and bonobos.

"Taken together, our results indicate that these social and cognitive differences between these two closely related species result from evolutionary changes in brain development," said Wobber. (ANI)

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