Preprint Review Version 1 Preserved in Portico This version is not peer-reviewed

The Evolution of Grooming and Hand Use in Primates: An Interdisciplinary Perspective

Version 1 : Received: 18 September 2019 / Approved: 20 September 2019 / Online: 20 September 2019 (06:39:59 CEST)

How to cite: Dunkel, A. The Evolution of Grooming and Hand Use in Primates: An Interdisciplinary Perspective. Preprints 2019, 2019090233. Dunkel, A. The Evolution of Grooming and Hand Use in Primates: An Interdisciplinary Perspective. Preprints 2019, 2019090233.


The evolution of manual grooming and its implications have received little attention in the quest to understand the origins of simian primates and their social and technical intelligence. All simians groom manually, whereas prosimians groom orally despite comparable manual dexterity between some members of the two groups. Simians also exhibit a variable propensity for the manipulation of inanimate, non-food objects, which has culminated in tool making and tool use in some species. However, lemuriform primates also seem capable of tool use with training. Furthermore, lemuriforms appear to understand the concept of a tool and use their own body parts as “tools”, despite not using inanimate objects. This suggests that prosimian primates are pre-adapted for proprioceptive object manipulation and tool use, but do not express these cognitive abilities by default. This essay explores the paleontological, anatomical, cognitive, ethological, and neurological roots of these abilities and attempts to explain this behavioural divide between simians and prosimians. Common misconceptions about early primate evolution and captive behaviours are addressed, and chronological inconsistencies with Machiavellian Intelligence are examined. A “licking to picking” hypothesis is also proposed to explain a potential link between manual grooming and object manipulation, and to reconcile the inconsistencies of Machiavellian Intelligence. Bayesian decision theory, the evolution of the parietal cortex and enhanced proprioception, and analogies with behavioural changes resulting from artificial selection may help provide new insights into the minds of both our primate kin and ourselves.


primate hand use; primate grooming; manual grooming; object manipulation; primate evolution; oral grooming; object play; tool use; Machiavellian Intelligence; Bayesian decision theory


Biology and Life Sciences, Ecology, Evolution, Behavior and Systematics

Comments (1)

Comment 1
Received: 26 September 2019
Commenter's Conflict of Interests: I am the author.
Comment: This review article was written at the invitation of the journal Animal Behaviour in 2012. Prior to submission, leading researchers in each of the fields discussed were invited to review and critique the sections relevant to their field, and all gave their approval and encouragement. These people included Todd M Preuss, Alison Jolly, John Fleagle, Marc Godinot, Ian Tattersall, and others.

The paper was rejected with few or no comments from the reviewers, and no alternative journal has been found.

However, the contents of this manuscript need to be considered. In it, I claim that tool use evolves not from large, social brains, but from the basic functions of the nervous system. *The body is a tool*, and when evolution focuses that internal awareness outward, brains can evolve to use objects as tools.

I am interested in collaboration to get this published.
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