Origins of Simian Intelligence The Licking to Picking Hypothesis Alex Dunkel Exotic Animal Training & Management Program, Moorpark College

Comparing Primates Simians: monkeys and apes Most simians are social Considered more intelligent Have larger neocortex Groom manually Prosimians: lemurs, lorises, tarsiers, etc. Some are social, others solitary Considered to be less intelligent Groom orally

Existing Hypotheses Foraging Hypotheses Examine correlation between ecology and brain size Have difficulty identifying the selective force by which simian intelligence evolved Most implicate brain structures other than the neocortex Not widely accepted

Existing Hypotheses (con.) Social Hypotheses Widely accepted and popularized Extended to other mammalian orders Focus on complexity of social behavior and group size Shortcomings: Do not sufficiently explain fidgeting and the manipulation of objects Inadequately explain why social lemurs lack the intelligence the hypotheses predict

The Licking to Picking Hypothesis Defining aspects of primate intelligence Manual manipulation of non-food items is key to our intelligence and ability to learn about our environment This requires highly dexterous appendages to manipulate objects, along with a drive to do so The Licking to Picking Hypothesis: A change in grooming style (from licking to picking) generalized to inanimate objects fidgeting Fidgeting resulted in non-foraging manipulation, while insight learning, abstract thought, and social learning (from the social hypotheses) created avenues for the creation and sharing of novel adaptive behaviors

Strepsirrhini Lemurs Lorises common primate ancestor Tarsiers New World Monkeys Old World Monkeys Apes Haplorrhini ProsimiansSimians Licking to Picking (con.) Change in grooming style occurs sometime after the split with tarsiers All descendant simians groom manually and manipulate non- food objects All descendant prosimians groom orally and do not manipulate non- food objects

Licking to Picking (con.) Simian intelligence is multifaceted Our tool use comes from our manipulation of non-food items, with new behaviors propagated through social learning Abstract thought and insight learning are separate, but overlapping types of intelligence This hypothesis is part of a more general view on the evolution of intelligence The evolution of complex systems usually requires preadaptations. Intelligence is no exception!

Licking to Picking (con.) In general terms, this hypothesis works with the social hypotheses to better explain the full gamut of animal intelligence. (They are inclusive!) SocialSolitary most simians, some corvids, elephants, social lemurs, hyenas, lions, psittacines, rats, dolphins, domestic dogs cephalopods, raccoons, orangutans The general concept, when used with the social hypotheses, explains the lack of object manipulation and fidgeting in social lemurs, but also explains intelligence gradients in other social animals. It better explains the intelligence of solitary animals, such as orangutans, cephalopods, and raccoons

Circumstantial Evidence Grooming behaviors are sometimes seen in simians during manual problem solving Fidgeting may possibly be related to intelligence in humans Fidgeting behaviors often include grooming behaviors Playing with hair Rubbing hands together Biting fingernails

Research Overview Observed social groups of various primates Counted instances of specific behavior types: Oral grooming Manual grooming Foraging manipulation Non-foraging manipulation Manual prehension Oral prehension Compared the frequency of behaviors between simians and prosimians Observed species: Propithecus verreauxi coquereli Varecia variegata rubra Lemur cattaPan troglodytesCebus apellaColobus guereza

Research Obstacles Clearly defining behavior criteria Counting instances of varying duration e.g. Prehension of small vs. large food items What constitutes non-foraging manipulation? Ambiguities in grooming definitions Does scratching qualify as grooming? Simian oral grooming Enrichment and enclosure design restrictions for simians affected observations

Results

Conclusion Primates that groom manually also manipulate non-food items and use their hands more for food acquisition Correlation does not imply causation Much more research is needed Need to look at the fossil record to see if more dexterous hands evolved when grooming changed

The following facilities graciously accommodated my observation time: Duke Lemur Center Los Angeles Zoo & Botanical Gardens Americas Teaching Zoo at Moorpark College Special thanks to the following people for their feedback and support: Gary & Cindy Wilson Acknowledgements And, of course, my troop – two very special lemurs who pointed out the obvious and inspired my research Obi & Janga

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