Fossil hominids

Human handedness is likely related to brain lateralization and major cognitive innovations in human evolution. Identifying handedness in the archaeological record is,
therefore, an important step in understanding our cognitive evolution. This thesis reports
on experiments in identifying knapper handedness in lithic debitage. I conducted a blind
study on flakes (n=631) from Acheulean handaxes replicated by right- and left-handed
flintknappers. Several flake characteristics significantly indicated handedness, with a
binary logistic regression correctly predicting handedness for 71.7% of the flakes.
However, other characteristics were not associated with handedness. This is a result of
personal knapping styles, as additional analyses show that individual knappers associate
with some attributes better than handedness does. Continued work on these methodologies will enable analysis of Paleolithic assemblages in the future, with the ultimate goal of tracking population-level hominid handedness rates through time and using them as a proxy for cognitive evolution and language acquisition.

The Paranthropus head is characterized by features traditionally thought to be related to heavy chewing. McCollum [Science 284 (1999) : 301-305] proposed that palatal thickening is a response to developmental integration between the mandibular ramus, oral and nasal functional matrices, and the vomer, which inserts onto the premaxilla in Paranthropus and causes the palate to thicken instead of rotate during vertical expansion. I tested whether palate thickness increases as a byproduct of differential increases in the sizes of the oral and nasal functional matrices compared to growth in the mandibular ramus. To do so, I collected 3D volume and landmark data from computed tomography (CT) scans of extant (Homo sapiens, Pan troglodytes, Gorilla gorilla, Pongo pygmaeus) and extinct taxa (Australopithecus and Paranthropus), and tested counterpart relationships for bones in the cranium using scaling analyses. Results suggest that developmental constraints related to growth counterpart relationships in the skulll are unlikely to affect palate thickness in the genus Paranthropus.

The timing of skeletal growth spurts in modern humans is unique among mammals. In modern humans, peak growth occurs after puberty during the adolescent period, whereas large-bodied non-human primates exhibit an earlier juvenile growth spurt. Based on limited data, previous researchers have suggested that Neanderthals experienced a late, modern human-like adolescent growth spurt. In this study, I examined the timing of stature and facial growth spurts in Neanderthals to test the hypothesis that Neanderthals grew like modern humans. In order to assess the timing of Neanderthal growth spurts, I plotted a non-human primate regression estimate of age at puberty onto Neanderthal stature and mandibular velocity growth curves. The mandibular growth curve exhibits a discernible growth spurt after puberty, reminiscent of the modern human adolescent growth spurt. Future research on additional regions of the skeleton is necessary to further refine this estimate for the timing of Neanderthal growth spurts.

Lithic projectile armatures represent a significant innovation over thrusted spears in the subsistence strategies of hominins. Previous researchers have disagreed over the timing of the appearance of projectile weapons in the archaeological record (Brooks 2006; Shea 2006). To discover when projectile technology first appears in the Levant, I have compared tip cross-sectional areas, weights, and tip penetrating angles (three variables useful for discriminating between projectile and thrusting weapons) of pointed Blades, Levallois points, and Mousterian points with analogs from known and suspected chipped stone projectile points. Results indicate that pointed Blades from Tabun and Skhul caves are statistically indistinguishable from other suspected projectile point types. Levallois and Mousterian points from Tabun and Skhul are also statistically indistinguishable from suspected projectile types when the lower halves of the populations are compared. Consequently, I conclude that points from Tabun and Skhul caves fall within the known and suspected range of variation of projectile point morphology.