Growth of Neanderthal infants from Krapina (120–130 ka), Croatia

Modern humans have a slow and extended period of childhood growth, but to what extent this ontogenetic pathway was present in Neanderthals is debated. Dental development, linked to the duration of somatic growth across modern primates, is the main source for information about growth and development in a variety of fossil primates, including humans. Studies of Neanderthal permanent teeth report a pace of development either similar to recent humans or relatively accelerated. Neanderthal milk teeth, which form and emerge before permanent teeth, provide an opportunity to determine which pattern was present at birth. Here we present a comparative study of the prenatal and early postnatal growth of five milk teeth from three Neanderthals (120 000–130 000 years ago) using virtual histology. Results reveal regions of their milk teeth formed quickly before birth and over a relatively short period of time after birth. Tooth emergence commenced towards the earliest end of the eruption schedules displayed by extant human children. Advanced dental development is consistent with expectations for Neanderthal infant feeding.

Dental caries in wild primates: interproximal cavities on anterior teeth

Dental caries has been reported in a variety of primates, although is still considered rare in wild populations. In this study, 11 catarrhine primates were studied for the presence of caries. A differential diagnosis of lesions found in interproximal regions of anterior teeth was undertaken, since they had been previously described as both carious and non-carious in origin. Each permanent tooth was examined macroscopically, with severity and position of lesions recorded. Two specimens were micro-CT scanned to assess demineralization. The differential diagnosis confirmed the cariogenic nature of interproximal cavities on anterior teeth (ICAT's). Overall results show 3.3% of teeth are carious, with prevalence varying among species from 0% to over 7% of teeth affected. ICAT's occurred in Pan troglodytes (9.8%), Gorilla gorilla gorilla (2.6%), Cercopithecus denti (22.4%), Presbytis femoralis (19.5%) and Cercopithecus mitis (18.3%). They make up 87.9% of carious lesions on anterior teeth. These results likely reflect dietary and food processing differences among species, but also between the sexes (e.g., 9.3% of teeth of female chimpanzees were carious vs. 1.8% in males). Processing cariogenic fruits and seeds with the anterior dentition (e.g., wadging) likely contributes to ICAT formation. Further research is needed on living populations to ascertain behavioral/dietary influences on caries occurrence in primates. Given the constancy of ICAT's in frugivorous primates, their presence in archaeological and paleontological specimens may shed light on diet and food processing behaviors in fossil primates.

Primates from the Baynunah Formation

Fossil primates of the Baynunah Formation are represented by only two cercopithecoid specimens: AUH 35, a male lower canine of an indeterminate cercopithecid from site JDH-3, and AUH 1321, a lower molar of a guenon from site SHU 2-2. Although rare, these cercopithecoid primates are significant in terms of their age and biogeographic implications. AUH 1321 is the earliest known guenon in the fossil record, and at ~8 – 6.5 Ma, it is also one of the earliest cercopithecines known. The age and geographic position of both specimens in the Arabian Peninsula supports late Miocene Eurasian dispersal scenarios for cercopithecoid primates out of Africa and through Arabia before the Messinian Crisis. Whether or not this dispersal included both cercopithecines (macaques) and colobines is unclear, and it re- mains possible that both groups also dispersed across the Mediterranean Basin or Straits of Gibraltar during the Messinian as well. Among the potential Arabian dispersal routes, there is perhaps some support for the southern path over the Straits of Bab el Mandeb based on the presence of ~8 – 5.5 Ma cercopithecine and colobine fossils in the East African fossil record, geographically close to the Horn of Africa.

Amphipithecine primates are stem anthropoids: cranial and postcranial evidence

Since their discovery in 1927, the phylogenetic status of the Myanmar amphipithecines has been highly debated. These fossil primates are recognized either as anthropoids or as adapiform strepsirrhines. This uncertainty was largely the consequence of a limited fossil record consisting mostly of jaw fragments but lacking the critical cranial elements that might resolve this debate. We report here cranial remains associated with an ulna from a single individual pertaining to the amphipithecine Ganlea megacanina . In addition to anthropoid-like dentognathic characters, Ganlea displays several ulna and skull features that testify to its anthropoid affinities (e.g. short subvertically oriented lacrimal duct, lacrimal foramen and bone inside the orbit, maxillary contribution to the lower orbital rim, fused metopic suture). By contrast to crown anthropoids, however, Ganlea lacks postorbital closure, confirming that postorbital closure appeared later than many anthropoid dentognathic characters and evolved convergently in extant tarsiers and anthropoids. Thus, amphipithecines must now be recognized as stem anthropoids offering a unique window on the early evolution of cranial and skeletal features in anthropoids, and reinforcing the hypothesis of an origin and early diversification of anthropoids in Asia.

Evolutionary Implications of Non-human Primate Diets

Extant non-human primates are our closest living relatives and knowledge of their diets serves as a focus for hypotheses about past diets. We now know that the diets of extant primates vary from almost total folivory to considerable faunivory. Subsistence strategies of extant primates and stable isotope ratio data constrain dietary scenarios for fossil primates, including hominins. Among extant primates, significant faunivory occurs only in species of <1 kg body weight. Among those >1 kg body weight, smaller primates feed on fruit or fruit with insects, and larger ones on fruit and foliage, including leaves, pith, stems, flowers, and bark. Fossil hominins fall into the size range for fruit and foliage-eating.