The neural and cognitive correlates of aimed throwing in chimpanzees: a magnetic resonance image and behavioural study on a unique form of social tool use
William D. Hopkins1,2,*, Jamie L. Russell2 and Jennifer A. Schaeffer2
Author Affiliations
1Department of Psychology and Neuroscience, Agnes Scott College, 141 E. College Avenue, Decatur, GA 30030, USA
2Division of Developmental and Cognitive Neuroscience, Yerkes National Primate Research Center, Atlanta, GA 30322, USA
*Author for correspondence
Abstract
It has been hypothesized that neurological adaptations associated with evolutionary selection for throwing may have served as a precursor for the emergence of language and speech in early hominins. Although there are reports of individual differences in aimed throwing in wild and captive apes, to date there has not been a single study that has examined the potential neuroanatomical correlates of this very unique tool-use behaviour in non-human primates. In this study, we examined whether differences in the ratio of white (WM) to grey matter (GM) were evident in the homologue to Broca's area as well as the motor-hand area of the precentral gyrus (termed the KNOB) in chimpanzees that reliably throw compared with those that do not. We found that the proportion of WM in Broca's homologue and the KNOB was significantly higher in subjects that reliably throw compared with those that do not. We further found that asymmetries in WM within both brain regions were larger in the hemisphere contralateral to the chimpanzee's preferred throwing hand. We also found that chimpanzees that reliably throw show significantly better communication abilities than chimpanzees that do not. These results suggest that chimpanzees that have learned to throw have developed greater cortical connectivity between primary motor cortex and the Broca's area homologue. It is suggested that during hominin evolution, after the split between the lines leading to chimpanzees and humans, there was intense selection on increased motor skills associated with throwing and that this potentially formed the foundation for left hemisphere specialization associated with language and speech found in modern humans.
COMENTÁRIO DESTE BLOGGER:
Jogar fezes contribuiu para a evolução da linguagem humana? Este comportamento lúdico, sem dúvida, foi responsável pelas palavras chulas de gente cujas bocas é mais suja do que latrinas. Realmente a evolução é muito mais inteligente do que você, idiota!
Jogar fezes contribuiu para a evolução da linguagem humana? Este comportamento lúdico, sem dúvida, foi responsável pelas palavras chulas de gente cujas bocas é mais suja do que latrinas. Realmente a evolução é muito mais inteligente do que você, idiota!
