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Fossils from the Fayum Depression, Egypt, are crucial for understanding anthropoid evolution due to the abundance of taxa and the time interval they represent (late Eocene to early Oligocene). Dietary and foraging behavioral interpretations suggest fruits were their dominant food source, although hard foods (e.g., seeds and nuts) and leaves could have been important dietary components for particular groups. In this study, we compare dental chipping patterns in five Fayum primate genera with chipping data for extant primates, to assess potential hard object feeding in early anthropoids. Materials and MethodsOriginal specimens were studied (Aegyptopithecus:n = 100 teeth;Parapithecus:n = 72,Propliopithecus:n = 99,Apidium:n = 82;Catopithecus:n = 68); with the number, severity, and position of chips recorded. Dental caries was also recorded, due to its association with soft fruit consumption in extant primates. ResultsTooth chipping was low across all five genera studied, with a pooled chipping prevalence of 5% (21/421). When split into the three anthropoid families represented, chipping prevalence ranged from 2.6% (4/154) in Parapithecidae, 6% (12/199) in Propliopithecidae, and 7.4% (5/68) in Oligopithecidae. Three carious lesions were identified in Propliopithecidae. DiscussionThe chipping prevalence is low when compared to extant anthropoids (range from 4% to 40%) and is consistent with a predominantly soft fruit diet, but not with habitual hard food mastication. The presence of caries supports consumption of soft, sugary fruits, at least in Propliopithecidae. Our results add support for low dietary diversity in early anthropoids, with soft fruits as likely dominant food sources.
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This content will become publicly available on May 22, 2026
Food-washing monkeys recognize the law of diminishing returns
Few animals have the cognitive faculties or prehensile abilities needed to eliminate tooth-damaging grit from food surfaces. Some populations of monkeys wash sand from foods when standing water is readily accessible, but this propensity varies within groups for reasons unknown. Spontaneous food-washing emerged recently in a group of long-tailed macaques (Macaca fascicularis) inhabiting Koram Island, Thailand, and it motivated us to explore the factors that drive individual variability. We measured the mineral and physical properties of contaminant sands and conducted a field experiment, eliciting 1282 food-handling bouts by 42 monkeys. Our results verify two long-standing presumptions: monkeys have a strong aversion to sand and removing it is intentional. Reinforcing this result, we found that monkeys clean foods beyond the point of diminishing returns, a suboptimal behavior that varied with social rank. Dominant monkeys abstained from washing, a choice consistent with the impulses of dominant monkeys elsewhere: to prioritize rapid food intake and greater reproductive fitness over the long-term benefits of prolonging tooth function.
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- Award ID(s):
- 1829315
- PAR ID:
- 10592495
- Publisher / Repository:
- eLife Sciences Publications Ltd
- Date Published:
- Journal Name:
- eLife
- Volume:
- 13
- ISSN:
- 2050-084X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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