New Chimpanzee Research Sheds Light on Human Evolution

Chimpanzee brains have equal halves, while human brains have a subtle twist with the left hemisphere longer than the right. Language ability is linked to the left hemisphere.

New research from the University of Edinburgh reveals that Chimpanzee brains may be more different from those of humans than was previously thought. The study explores the phenomenon of brain torque, in which the human brain shows slight twisting. Until now, this was also thought to be true of other primates.

The pattern of asymmetry in human brains could be a unique feature of our species and may hold the key to explaining how we first developed language ability, according to a newly published study. The new findings are based on brain scans of humans and previously collected data from chimpanzees and could help scientists understand how our brains evolved and why asymmetry is vital to human development.

Researchers led by the University of Edinburgh studied images from an existing bank of chimpanzee brain scans held in the USA. Comparisons were made with the brains of humans who were scanned using similar equipment, known as magnetic resonance imaging (MRI), and identical experimental procedures.

Chimpanzee brains were shown to be made up of equal halves, or hemispheres, whereas in human brains a subtle twist was present. Asymmetry was seen in humans, but not chimpanzees, with the left hemisphere longer than the right. Language ability has been linked to areas within the left hemisphere of the brain and has also been associated with asymmetry.

The study helps shed light on how humans developed skills for language, and the researchers suggest that a new study of particular brain areas related to language using the same image bank could aid in the understanding of this.

Neil Roberts, Professor of Medical Physics and Imaging Science at the University of Edinburgh, said: “Our findings highlight a special, subtle feature of the human brain that distinguishes us from our closest primate cousins and may have evolved rapidly. Better understanding of how this came about in our evolution could help explain how humans developed language.”

The study was published in the journal NeuroImage. It was carried out in collaboration with researchers at the University of Oxford, as well as in China and the US.

Reference: “Human torque is not present in chimpanzee brain” by Xiang Li, Timothy J. Crow, William D. Hopkins, Qiyong Gong and Neil Roberts, 5 November 2017, NeuroImage.
DOI: 10.1016/j.neuroimage.2017.10.017