A shrew-sized origin for primates.
The origin of primates has had a long history of discussion and debate, with few ever considering the impact of the original body weight on subsequent primate adaptive radiations. Here, I attempt to reconstruct early primate evolution by considering the initial size of primates as well as the critical functional-adaptive events that had to occur prior to the early Eocene. Microcebus is often viewed as a living model, and thus 40-65 g might represent a practical ancestral weight for the origin of primates. I consider a smaller original body weight, likely 10-15 g in actual size, and I address the biological implications for shrew-sized primates by comparing the behavioral ecology of mouse lemurs, our smallest living primates, to another tiny-sized mammalian group, the shrews (Family Soricidae). Several behavioral and ecological characteristics are shared by shrews and mouse lemurs, and several mammalian trends are evident with decreased size. I suggest that a shrew-sized ancestral primate would have had high metabolic, reproductive, and predation rates, relatively low population densities, and a dispersed and solitary existence with a promiscuous mating system. Although small mammals like shrews provide insights concerning the ancestral size of primates, primate origins have always been tied to arboreality. I assess other potential arboreal models such as Ptilocercus and Caluromys. By combining all of this information, I try to sequence the events in a functional-adaptive series that had to occur before the early Eocene primate radiations. I suggest that all of these important adaptive events had to occur at a small body size below 50 g.
Gebo
Daniel L
DL
Department of Anthropology, Northern Illinois University, DeKalb, Illinois 60115, USA. dgebo@niu.edu
D000222:Adaptation, Physiological; D000717:Anatomy, Comparative; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001522:Behavior, Animal; D005075:Biological Evolution; D049628:Body Size; D001921:Brain / Q000033:anatomy & histology; D016565:Cheirogaleidae / Q000033:anatomy & histology / Q000502:physiology; D004777:Environment; D005260:Female; D005580:Fossils; D008124:Locomotion / Q000502:physiology; D008297:Male; D008660:Metabolism / Q000502:physiology; D010828:Physiology, Comparative; D011323:Primates / Q000033:anatomy & histology* / Q000502:physiology; D012726:Sexual Behavior, Animal; D012788:Shrews / Q000033:anatomy & histology* / Q000502:physiology; D012919:Social Behavior