The scientist: Klaus Zuberbuhler, professor of psychology at the University of St. Andrews in Scotland, scientific director of the Budongo Conservation Field Station in Uganda, co-director of the Taï Monkey Project in the Ivory Coast, and deputy director of the Living Links to Human Evolution Research Center at the Edinburgh Zoo.

The idea: Scientists investigating the evolution of human intelligence often look at our closest ape relatives for insights. "By comparing chimpanzees and bonobos with modern humans, we can draw inferences about behavioral, motivational and cognitive traits that are ancestral, or shared with apes, and traits that are derived, or uniquely human, evolved during the last 5 to 6 millions years," Zuberbuhler says.

Ideally, researchers would like to see what effect genetic variations have on the behavior, motivations and cognition of healthy, normally developed individuals both within a species and across closely related species. Gene defects that lead to abnormal conditions "usually provide little help in understanding of how genes influence variation in normal individuals," Zuberbuhler says.

The problem: Ideally, to experimentally study each of the many genetic factors linked with intelligence, one would need individuals representing each of the untold numbers of combinations of these genes to observe the outcomes — and, really, multiples of each combination for experiments. Scientists would probably also not only like to see what happens with these combinations in one species, but compare results across closely related species, such as humans, bonobos and chimpanzees. Aside from the sheer logistical difficulties involved with finding or breeding such combinations, there come the moral and ethical questions of experimenting on model organisms with the level of intelligence one would like to study.

The solution? Scientists are currently surveying thousands of genes across humans and closely related species to see which might have changed over time and thus be linked with the evolution of human intelligence. They are also focusing on variations in genes that are strongly linked with cognition, such as FOXP2, Zuberbuhler says, which is associated with speech and language.

Image of Klaus Zuberbuhler from his Web page.


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About the Author: Charles Q. Choi is a frequent contributor to Scientific American. His work has also appeared in The New York Times, Science, Nature, Wired, and LiveScience, among others. In his spare time he has traveled to all seven continents. Follow him on Twitter @cqchoi.

The views expressed are those of the author and are not necessarily those of Scientific American.