Bonobo diet of aquatic greens may hold clues to human evolution

Study offers a possible answer on how our human ancestors may have met their nutritional needs of iodine in the Congo basin

Researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have for the first time observed bonobos in the Congo basin searching for and eating iodine-rich aquatic plants in the swamps. Iodine is a critical nutrient for brain development and higher cognitive abilities. According to the research team, these observations may explain how the nutritional needs of prehistoric humans in the region were met.

"Our results have implications for our understanding of the immigration of prehistoric human populations into the Congo basin", says lead author Gottfried Hohmann from the Max Planck Institute for Evolutionary Anthropology. "Bonobos as a species can be expected to have similar iodine requirements to humans, so our study offers - for the first time - a possible answer on how pre-industrial human migrants may have survived in the Congo basin without artificial supplementation of iodine."

The researchers made behavioural observations of two bonobo communities in the LuiKotale forest in Salonga National Park, Democratic Republic of Congo. These observations were combined with data on the iodine content of plants eaten by bonobos from an ongoing study by the Leibniz Institute for Zoo and Wildlife Research, Berlin. They found that the aquatic herbs consumed by bonobos are a surprisingly rich natural source of iodine in the Congo basin, a region that was previously thought to be scarce in iodine sources.

Aquatic herbs could serve as iodine source in continental environments

"Evolutionary scenarios suggest that major developments of human evolution are associated with living in coastal areas, which offer a diet that triggered brain development in hominins", says Hohmann. "The results of our study suggest that consumption of aquatic herbs from swamps in forest habitat could have contributed to satisfying the iodine requirements of hominin populations used to diets prevalent in coastal environments." Hohmann adds: "Our report potentially answers the question of how apes obtain iodine from natural food sources, when many populations inhabit areas considered to be iodine deficient. Other apes such as chimpanzees and gorillas have also been observed eating aquatic herbs, which suggests that they could be obtaining essential iodine from these sources."

The authors caution that without data on the iodine status of wild bonobos, it is difficult to tell how much iodine they absorb, although given the high concentrations in the herbs, it is likely to be substantial. The authors also stress that the iodine concentrations obtained at the field site of LuiKotale may not be reflective of the entire Congo basin.

AK/SJ