The study of culture in wild animals has received wide theoretical and empirical attention, providing preliminary evidence of at least rudimentary culture across a broad range of taxa. However, the majority of previous studies of animal cultural behavior have focused on demonstrating the existence of behavioral variants across study sites, armed only with an assumption that ecological and genetic alternatives are unlikely to sufficiently explain observed geographic variation in behavior. Moreover, previous studies have reported the presence of behavioral variation at the level of the population, without first confirming the presence of such variation in individual repertoires, which could create artificial patterns within or between populations.

Using more rigorous methods than previous studies, I examined rarely tested alternatives to field-based claims of cultural repertoire variation based on ecological heterogeneity and genetic variation. This dissertation relies on a natural experiment to compare two wild orangutan populations. Sungai Lading, a previously unstudied, high-density population of wild Pongo pygmaeus wurmbii, was compared to Tuanan, a P.p.wurmbii population separated from Sungai Lading by an impassable river barrier, but ranging in a broadly similar habitat. Preliminary genetics results indicate that at least some individuals from both sites cluster in the same mitochondrial subclade and that low levels of gene flow must have occurred between the two sites. Even after applying rigorous controls for variation in sampling intensity for individual orangutans, several differences in innovative behaviors exhibited at each site were identified, many of which occurred in the nesting context.

The orangutan is a model taxon for such an investigation, because wild populations exhibit a wide range of sociality, which has been linked to opportunities for social learning. Comparisons between the Tuanan and Sungai Lading populations indicated that cultural variants observed at only one site clustered significantly by population, although only dietary differences were unique at both sites. Orangutans at Sungai Lading maintain significantly lower rates of female-female association and lower individual repertoire sizes of putative cultural variants, a result that is consistent with the possibility that the orangutans of Sungai Lading may have reduced opportunities for social learning as a result of severe population compression, which could constrain opportunities for cultural transmission of key innovative behaviors.

From a broader perspective, the patterns revealed in this study strongly suggest that the last common ancestor of Homo and Pongo shared culturally modified behavior. They further suggest that the extent of cumulative cultural behavior in humans may surpass that of orangutans as a result of lost opportunities for social transmission, owing to varying degrees of limited association among group members.

Humans are more carnivorous than other hominoids. It has been hypothesized that, during the evolution of this increased carnivory, hominins transitioned through a scavenging niche made viable by certain carnivoran taxa (especially sabertooths) that may have lacked the morphology necessary to fully utilize all parts of carcasses (e.g., marrow), therefore leaving an open niche in the form of high-quality scavengable remains available for hominins. In this dissertation, I examine the postcanine dentition of modern carnivorans, using quantifications of occlusal radii of curvature and intercuspid notches, and study the correlation of this morphology with carcass-processing behavior. I use these correlations to deduce the carcass-processing capabilities of the Plio-Pleistocene carnivores of South Africa (a guild for which we have a good appreciation of taxonomic diversity, and that existed at an important time during the evolution of our lineage - possibly the time that we transitioned into that guild), and compare these results with those of previous studies that relied on more conventional morphological measures.

Both radius of curvature and intercuspid notch data do a good job of separating taxa by dietary category, revealing subtle patterns including possible differences in the carcass-processing abilities of fossil and modern members of some extant species. Other strong trends confirm that the "hunting-hyena," Chasmaporthetes, was probably a hypercarnivore, and not a durophage like its modern confamilial taxa. Somewhat surprisingly, results do not support the hypothesis that sabertooth felids were more hypercarnivorous than modern felids. Furthermore, though the sympatric hypercarnivorous taxa were more numerous, so to were the durophageous taxa, with one taxon, Pachycrocuta, probably exceeding the durophageous capabilities of modern durophages.

As such, this dissertation shows no evidence that members of the paleo-carnivore guild were capable of producing higher quality scavengable carcasses than are modern carnivorans, and thus, based on these analyses of fossil carnivorans, it does not appear that high-quality scavengable remains were more available in the Plio-Pleistocene than there are today. Therefore, though there is clear evidence from other sources that hominins did scavenge at least occasionally, this dissertation does not support the hypothesis that there was an open niche consisting of high-quality scavengable remains.

The pace of life history is highly variable across mammals, and several evolutionary biologists have theorized that the tempo of a species' life history is set by external factors. These factors, such as food availability and predation pressure, determine mortality rates. In turn, mortality rate determines the age at maturity. High mortality rate results in early age at maturity; individuals must grow and reproduce quickly because of the high risk of death. Conversely, a low mortality rate is allows individuals to prolong their growth period and reproduce slowly. This theory assumes that growth rates are constant across species, and thus body size is determined by mortality rates.

This project posits that the intrinsic characteristics of species set the pace of life history. Among anthropoids, there is a great deal of variation in growth rates and the pace of life history relative to body size. The hypotheses proposed by this project state that the degree of encephalization in a species determines the growth rates, the length of the growth period, and the adult lifespan. Growing a large brain is costly and requires a prolonged period of development. However, a large brain has the benefit of reducing mortality by facilitating cognitive strategies for food procurement and predator avoidance. This cost/benefit balance results in the pattern of life-history variation in which mortality rates are correlated with the length of the growth period. However, the causal arrows are reversed; instead of the mortality rate determining the age at maturity and consequently the size of the species, the relative brain size of the anthropoid determines the mortality rate and the age maturity.

These hypotheses were tested by determining the body and brain growth trajectories of thirteen anthropoids, and compiling life-history data from long-term studies of these species in the wild. Multi-variate analyses demonstrated that extensive brain growth, whether through prolonged duration or rapid growth rates, results in slow body-growth rates during the juvenile period and delayed age at maturity. In addition, encephalization results in longer adult lifespan. Therefore, this project demonstrated that intrinsic characteristics of anthropoid species determine the pace of their life histories.