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Proc Natl Acad Sci U S A. 2018 Feb 6;115(6):E1108-E1116. doi: 10.1073/pnas.1719666115. Epub 2018 Jan 22.

A neurochemical hypothesis for the origin of hominids.

Author information

1
Department of Anthropology, Kent State University, Kent, OH 44242; mraghant@kent.edu olovejoy@aol.com.
2
School of Biomedical Sciences, Kent State University, Kent, OH 44242.
3
Department of Anthropology, Kent State University, Kent, OH 44242.
4
Department of Pharmaceutical Sciences, Northeast Ohio Medical University, Rootstown, OH 44272.
5
Laboratory of Quantitative Neuromorphology, Department of Psychology, Colorado College, Colorado Springs, CO 80903.
6
Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029.
7
Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029.
8
New York Consortium in Evolutionary Primatology, New York, NY 10024.
9
Department of Anthropology, The George Washington University, Washington, DC 20052.
10
Center for the Advanced Study of Human Paleobiology, The George Washington University, Washington, DC 20052.
11
Department of Anthropology, Columbia University, New York, NY 10027.

Abstract

It has always been difficult to account for the evolution of certain human characters such as language, empathy, and altruism via individual reproductive success. However, the striatum, a subcortical region originally thought to be exclusively motor, is now known to contribute to social behaviors and "personality styles" that may link such complexities with natural selection. We here report that the human striatum exhibits a unique neurochemical profile that differs dramatically from those of other primates. The human signature of elevated striatal dopamine, serotonin, and neuropeptide Y, coupled with lowered acetylcholine, systematically favors externally driven behavior and greatly amplifies sensitivity to social cues that promote social conformity, empathy, and altruism. We propose that selection induced an initial form of this profile in early hominids, which increased their affiliative behavior, and that this shift either preceded or accompanied the adoption of bipedality and elimination of the sectorial canine. We further hypothesize that these changes were critical for increased individual fitness and promoted the adoption of social monogamy, which progressively increased cooperation as well as a dependence on tradition-based cultural transmission. These eventually facilitated the acquisition of language by elevating the reproductive advantage afforded those most sensitive to social cues.

KEYWORDS:

Ardipithecus; basal ganglia; dopamine; hominin; neurotransmitter

PMID:
29358369
PMCID:
PMC5819450
DOI:
10.1073/pnas.1719666115
[Indexed for MEDLINE]
Free PMC Article

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