The preferential use of one hand over the other to perform certain tasks is a feature that reflects the functional division of the brain in the execution of a series of tasks. These findings are especially important from an evolutionary point of view and could explain the emergence of language or technology when this feature is present in humans.
The preferential use of one hand over the other to perform certain tasks is a feature that reflects the functional division of the brain in the execution of a series of tasks. These results are especially important from an evolutionary point of view and could explain the emergence of language or technology when this feature is present in humans.
Over the past 25 years, the interest aroused from the study of brain lateralization in primates and other animals has been enormous. Historically, it was assumed that the cerebral hemispheric specialization of the human being was a feature specific only to our species. The dominance of our left hemisphere over the right in the process of linguistic information also influenced the preferential use of the right hand over the left in everyday activities. However, in recent years these theories have been questioned. Increasingly asymmetries became evident in the functioning of the brain and in various manual and non-manual behaviors in many species of vertebrates: fish, reptiles, amphibians, birds, whales, cattle, etc.
With regards to primates, and specifically to chimpanzees, the picture was somewhat different. Some American scientists around a decade ago claimed that chimpanzees exhibited skills similar to those of human beings. Others argued that the lateralization of the brain was one of the characteristics defining and differentiating us as a species compared to other animals. According to these authors, the results concluded from investigations undertaken on right-handed chimpanzees who been held in captivity in research laboratories could not be applied to wild chimpanzees, where manual preference was almost totally absent.
However, recent work on the subject has shed more light on the chaos. Researchers from four Catalan institutions (the Mona Foundation, the Catalan Institute of Human Paleoecology and Social Evolution, the University of Rovira and Virgili and the University of Barcelona) carried out a study on 114 chimpanzees living in naturalistic environments at Primate Recovery Centres in Chimfunshi (Zambia) and at the Mona Foundation (Riudellots de la Selva, Girona). This pioneering study found that whilst undertaking complex tasks involving the use and coordination of both hands, chimpanzees portray a pattern of manual asymmetry similar to humans. Furthermore, as in humans, female chimpanzees are more skillful than males, suggesting that, as in our species, there are shared biological factors (genetic and hormonal) regulating the functioning of our brain.
In the words of Miquel Llorente, responsible for this project: "These characteristic evolutionary roots, so human-like according to some, are so much more profound than previously thought, with their appearance dating back to the last 6 or 7 million years, when the divergence between chimps and hominids began¨. Llorente continues: "this explains why our manual asymmetry is not due to language. Why else would they be lateralized in the same way as us? Our results are not merely a reflection of the demystification of many of the peculiarities of our species in recent years. First was the use of instruments, then a complex social life. Currently, we have found that the brains of chimpanzees possess the same linguistic areas as humans do. It has been shown that in actions requiring the use of tools or the coordination of both hands a chimpanzee will preferably use his right hand, as our species does. From our point of view, the importance here has been the discovery that we both have a similar type of brain function and this has been the foundation on which man has been able to build an extremely flexible, powerful and complex technological and communication system. Our species has done no more than take advantage of the neuroanatomical structures already possessed by our ancestors and allowing us the huge potential in the use, manufacture and design of complex instruments never before seen in the course of evolution.”
The results of this investigation were released in the American Journal of Primatology:
Population-level right-handedness for a coordinated bimanual task in naturalistic housed chimpanzees: replication and extension in 114 animals from Zambia and Spain
by Miquel Llorente, David Riba, Laia Palou, Lara Carrasco, Marina Mosquera, Montserrat Colell, Olga Feliu
Article first published online: 15 OCT 2010
DOI: 10.1002/ajp.20895