Origins of Simian Intelligence

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

2. 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

3. 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

4. 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

5. 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

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

7. 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!

8. 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!) • 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

9. 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

10. Oral grooming • Manual grooming • Foraging manipulation • Non-foraging manipulation • Manual prehension • Oral prehension Propithecus verreauxi coquereli Varecia variegata rubra Lemur catta Pan troglodytes Cebus apella Colobus guereza Research Overview • Observed social groups of various primates • Counted instances of specific behavior types: • Compared the frequency of behaviors between simians and prosimians • Observed species:

11. 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

12. Results

13. 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

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

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