Do species populations really start small? New perspectives from the Late Neogene fossil record of African mammals.

This analysis of all known African larger mammals of the past 10 Myr offers new perspectives on the geographical circumstances of speciation. Our central question is: does the fossil evidence support the idea that most new species start as small populations and, if true, how long is the average growth interval until species are established at their mean later size? This simple question is important to unravelling the competing claims of rival models of speciation. We approached it by direct use of fossil data, which, to our knowledge, has not been done previously. We compared the numbers of fossil site records, as a proxy for magnitude of geographical spread, between survivorship intervals across all species. The results show that the average mammal species has indeed started its life in a relatively small population, and thereafter increased rapidly in geographical spread to reach its long-term equilibrium abundance by about 1 million years after origin. Some theoretical implications of these results are discussed.

Craniometric variation in a population of mantled howler monkeys (Alouatta palliata): evidence of size selection in females and growth in dentally mature males.

A large body of work on monkey cranial metrics (involving conclusions about interspecific variation, sexual dimorphism, and ontogeny) depends on the assumptions that growth effectively ceases with dental maturity and that intraspecific variation is negligible. We test these assumptions by examining variation in 39 measurements of 166 dentally mature Alouatta palliata skulls from animals found dead on Barro Colorado Island (BCI), Panama. We also investigate whether this population is under size-based selection, since our found-dead sample reflects the natural mortality in this population. The sample was divided into three age stages by occlusal wear (A-C, least to most wear). Female stage A means are significantly smaller than female stage B means for three cranial measures. Female stage B means are significantly smaller than female stage C means for five cranial measures. Male stage A means are significantly smaller than male stage B means for 21 cranial measures. Multivariate analyses confirm this trend of expansion between adult age stages. The dental metric and suture closure data suggest that the cranial expansion in females is due to size-based selection, while the cranial expansion in males is due to significant growth after dental maturity. Sexual dimorphism ratios are highly variable across different samples of A. palliata, indicating that dimorphism varies between populations of this species. These results provide insight into the selective forces operating on the BCI howlers and challenge the validity of the many studies which pool subspecies and assume growth ceases with maturity.

Fijian cannibalism: osteological evidence from Navatu.

The hypothesis that the human remains from the Navatu midden (50 BC to AD 1900) in Fiji represent cannibalized individuals was tested by an analysis of the skeletal remains. The site includes formal human burials and a separate, contemporaneous midden containing commingled fragmentary human and nonhuman bones. All remains were examined for a variety of modifications. The medium mammal and human remains in the midden have similar modifications: ancient breaks (92% of midden human specimens and 88% of medium mammal specimens), burning (29% and 11%), crushing (1% and 1%), cutmarks (9% and 8%), peeling (4% and 1%), and percussion pits (1% and 1%). The human burials (for which cannibalism had not been hypothesized) are essentially unmodified except for some breakage. The pattern of element representation and low incidence of animal bitemarks rules out carnivores and rodents as major modifiers of the assemblage. The breakage patterns, element representation, light weathering, and rarity of random striae indicate that sediment pressure, wave action, weathering, and trampling did not significantly alter the remains. The modifications of the midden human and nonhuman remains generally correspond in type and frequency. The evaluation of the assemblage's taphonomic history suggests that most of the modifications were caused by humans. The Navatu midden human sample does not resemble assemblages interpreted as secondary burials with defleshing, nor does it resemble violence-derived assemblages. The burials at Navatu and other Fijian sites indicate that the various noncannibalistic Fijian mortuary rituals do not mimic butchery and consumption. Therefore, the hypothesis of cannibalism at Navatu is supported.

Hypoglossal canal size and hominid speech.

The mammalian hypoglossal canal transmits the nerve that supplies the motor innervation to the tongue. Hypoglossal canal size has previously been used to date the origin of human-like speech capabilities to at least 400,000 years ago and to assign modern human vocal abilities to Neandertals. These conclusions are based on the hypothesis that the size of the hypoglossal canal is indicative of speech capabilities. This hypothesis is falsified here by the finding of numerous nonhuman primate taxa that have hypoglossal canals in the modern human size range, both absolutely and relative to oral cavity volume. Specimens of Australopithecus afarensis, Australopithecus africanus, and Australopithecus boisei also have hypoglossal canals that, both absolutely and relative to oral cavity volume, are equal in size to those of modern humans. The basis for the hypothesis that hypoglossal canal size is indicative of speech was the assumption that hypoglossal canal size is correlated with hypoglossal nerve size, which in turn is related to tongue function. This assumption is probably incorrect, as we found no apparent correlation between the size of the hypoglossal nerve, or the number of axons it contains, and the size of the hypoglossal canal in a sample of cadavers. Our data demonstrate that the size of the hypoglossal canal does not reflect vocal capabilities or language usage. Thus the date of origin for human language and the speech capabilities of Neandertals remain open questions.

Brief communication: prehistoric dentistry in the American southwest: a drilled canine from Sky Aerie, Colorado.

A prehistoric Native American mandible from a Fremont site (circa AD 1025) in Colorado has a conical pit in the worn occlusal surface of the lower right canine. Natural causes for this modification are ruled out by the presence of internal striae, a finding confirmed by experimental replication. The canine was artificially drilled before the individual's death and is associated with a periapical abscess. This is one of a very few examples of prehistoric dentistry in the world, and the first from the American Southwest.