Washington:Scientists from Duke University and the University of Zurich have come to the conclusion that there is an evolutionary connection between available food supplies and brain size.

In a study involving orang-utans living on the Indonesian islands of Borneo and Sumatra, Andrea Taylor and Carel van Schaik have suggested that temporary, unavoidable food scarcity may cause a decrease in brain size, perhaps accompanied by only a small or subtle decrease in body size.

The study, which appears in the online version of the Journal of Human Evolution, quoted both Taylor and van Schaik as saying that this was the first such study to demonstrate a relationship between relative brain size and resource quality in primates.

“Compared to other tissues, brain tissue is metabolically expensive to grow and maintain. If there has to be a trade-off, brain tissue may have to give,” Taylor said.

“The study suggests that animals facing periods of uncontrollable food scarcity may deal with that by reducing their energy requirement for one of the most expensive organs in their bodies: the brain,” van Schaik added.

“Such a theory is vital for understanding what happened during human evolution, where, relative to our ancestors, our lineage underwent a threefold expansion of brain size in a few million years,” both said.

Both found that nutritionally well-off Sumatran orang-utans differed most strikingly from Pongo pygmaeus morio, one of the three sub-species occupying Borneo, where soils are poorer, access to fruit is most iffy and the impact of El Niño is significant.

In previous studies, reported in the April 2006 issue of the Journal of Human Evolution, Taylor found evidence of northeast Borneo orang-utans having stronger jaws than orang-utans in other parts of Borneo or Sumatra.

Taylor is an assistant professor at Duke’s departments of Biological Anthropology and Anatomy and of Community and Family Medicine. Van Schaik directs the University of Zurich’s Anthropological Institute and Museum, and he also is an adjunct professor of biological anthropology and anatomy at Duke, where he had worked for 15 years.