Robert G. Franciscus

Peştera cu Oase 2 and the cranial morphology of early modern Europeans

Between 2003 and 2005, the Peştera cu Oase, Romania yielded a largely complete early modern human cranium, Oase 2, scattered on the surface of a Late Pleistocene hydraulically displaced bone bed containing principally the remains of Ursus spelaeus. Multiple lines of evidence indicate an age of ≈40.5 thousand calendar years before the present (≈35 ka 14C B.P.). Morphological comparison of the adolescent Oase 2 cranium to relevant Late Pleistocene human samples documents a suite of derived modern human and/or non-Neandertal features, including absence of a supraorbital torus, subrectangular orbits, prominent canine fossae, narrow nasal aperture, level nasal floor, angled and anteriorly oriented zygomatic bones, a high neurocranium with prominent parietal bosses and marked sagittal parietal curvature, superiorly positioned temporal zygomatic root, vertical auditory porous, laterally bulbous mastoid processes, superiorly positioned posterior semicircular canal, absence of a nuchal torus and a suprainiac fossa, and a small occipital bun. However, these features are associated with an exceptionally flat frontal arc, a moderately large juxtamastoid eminence, extremely large molars that become progressively larger distally, complex occlusal morphology of the upper third molar, and relatively anteriorly positioned zygomatic arches. Moreover, the featureless occipital region and small mastoid process are at variance with the large facial skeleton and dentition. This unusual mosaic in Oase 2, some of which is paralleled in the Oase 1 mandible, indicates both complex population dynamics as modern humans dispersed into Europe and significant ongoing human evolution once modern humans were established within Europe.

Cervical vertebrae maturation method: poor reproducibility.

INTRODUCTION The cervical vertebrae maturation (CVM) method has been advocated as a predictor of peak mandibular growth. This method relies on the clinicians ability to determine the stage of maturation of the vertebrae. Careful examination of reports of this technique shows methodologic flaws that can lead to inflated levels of reproducibility. The purpose of this study was to evaluate the reproducibility of CVM stage determination by using a more stringent methodology. METHODS Ten practicing orthodontists, trained in the CVM method, evaluated 30 individual and 30 pairs of cephalometric radiographs in 2 sessions to determine the CVM stage. Interobserver and intraobserver reliability was determined by using the Kendall coefficient of concordance and the weighted kappa statistic. RESULTS All degrees of interobserver and intraobserver agreement were moderate (Kendalls W, 0.4-0.8). Interobserver agreement levels for CVM staging of the 10 orthodontists at both times were below 50%. Agreement improved marginally with the use of 2 longitudinal radiographs. Intraobserver agreement was only slightly better; on average, clinicians agreed with their own staging only 62% of the time. CONCLUSIONS Based on these results, we cannot recommend the CVM method as a strict clinical guideline for the timing of orthodontic treatment.

Internal nasal floor configuration in Homo with special reference to the evolution of Neandertal facial form

The presence of a steeply sloping or depressed nasal floor within the nasal cavity of Neandertals is frequently mentioned as a likely specialization or autapomorphy. The depressed nasal floor has also been seen as contributing to a relatively more capacious nasal cavity in Neandertals, which is tied to cold-climate respiratory adaptation and energetics. These observations have been limited largely to a relatively few intact crania, and the character states associated with this trait have not been as precisely codified or analyzed as those published for Plio-Pleistocene hominins (McCollum et al., 1993, J. Hum. Evol. 24, 87; McCollum, 2000, Am. J. Phys. Anthrop. 112, 275). This study examines the internal nasal floor topography in complete crania and isolated maxillae in European, west Asian, and African fossil Homo (n=158) including 25 Neandertals, and a wide range of recent humans from Europe, the Near East, and Africa (n=522). The configuration of the internal nasal floor relative to the nasal cavity entrance is codified as: 1) level, forming a smooth continuous plane; 2) sloped or mildly stepped; or 3) bilevel with a pronounced vertical depression. The frequency of these nasal floor configurations, and their relationship to both nasal margin cresting patterning and a comprehensive set of nasofacial metrics is examined. Neandertals show a high frequency of the bilevel (depressed) configuration in both adults and subadults (80%), but this configuration is also present in lower frequencies in Middle Pleistocene African, Late Pleistocene non-Neandertal (Skhul, Qafzeh), and European Later Upper Paleolithic samples (15%-50%). The bilevel configuration is also present in lower frequencies (ca. 10%) in all recent human samples, but attains nearly 20% in some sub-Saharan African samples. Across extinct and extant Homo (excluding Neandertals), internal nasal floor configuration is not associated with piriform aperture nasal margin patterning, but the two are strongly linked in Neandertals. Variation in internal nasal floor configuration in recent humans is primarily associated with internal nasal fossa breadth and nasal bridge elevation, whereas in fossil hominins, it is associated primarily with variation in facial height. Cold-climate and activity-related thermal adaptation as an explanation for the high frequency of pronounced nasal floor depression in Neandertals is inconsistent with all available data. Alternatively, variation in internal nasal floor configuration is more likely related to stochastically derived populational differences in fetal nasofacial growth patterns that do not sharply differentiate genus Homo taxa (i.e., cladistically), but do phenetically differentiate groups, in particular the Neandertals, especially when considered in combination with other nasofacial features.

The paradox of a wide nasal aperture in cold-adapted Neandertals: a causal assessment

Neandertals have been characterized as possessing features indicative of cold-climate adaptation largely based on ecogeographical morphological patterning found in recent humans. Interestingly, one character that deviates from this pattern is a relatively wide nasal aperture. The ecogeographical patterning of the nasal aperture in recent humans would predict instead that Neandertals should exhibit reduced nasal breadth dimensions. To explain this apparent anomaly it has been argued that a reduction in Neandertal nasal breadth was not possible due to dentognathic constraints on their midfaces via large anterior palatal breadth dimensions, especially large intercanine distances. A complicating factor in understanding the relationship between anterior palate breadth and nasal breadth is that both measurements are also correlated with facial prognathism. It is, therefore, unknown to what degree the relationship between anterior palate breadth and nasal breadth in Neandertals is a function of the pleisiomorphic retention of a prognathic facial skeleton. We used path analysis to test for a causal relationship between intercanine breadth and nasal breadth taking into account the potential effect of facial projection and facial prognathism (i.e., basion-nasion length and basion-prosthion length) using a large sample of geographically diverse recent and fossil Homo. Additionally, we examined the ontogenetic relationship between nasal breadth and intercanine breadth using a longitudinal human growth series to determine whether these variables exhibit similar growth trajectories. The results of these analyses indicate a weaker association between intercanine breadth and nasal breadth than expected, and that more variation in nasal breadth can be explained through basion-prosthion length rather than anterior palatal breadth dimensions. Moreover, the ontogenetic development of anterior palate breadth does not correspond to the growth trajectory of the breadth of the nose. These results explain the apparent paradox of wide piriform apertures in generally cooler climate-adapted Neandertals without resorting to dentognathic constraints, and provide additional insight into both the adaptive and nonadaptive (i.e., neutral) basis for Neandertal facial evolution.

Shanidar 3 Neandertal Rib Puncture Wound and Paleolithic Weaponry

Since its discovery and initial description in the 1960s, the penetrating lesion to the left ninth rib of the Shanidar 3 Neandertal has been a focus for discussion about interpersonal violence and weapon technology in the Middle Paleolithic. Recent experimental studies using lithic points on animal targets suggest that aspects of weapon system dynamics can be inferred from the form of the bony lesions they produce. Thus, to better understand the circumstances surrounding the traumatic injury suffered by Shanidar 3, we conducted controlled stabbing experiments with replicas of Mousterian and Levallois points directed against the thoraces of pig carcasses. Stabs were conducted under both high and low kinetic energy conditions, in an effort to replicate the usual impact forces associated with thrusting spear vs. long-range projectile weapon systems, respectively. Analysis of the lesions produced in the pig ribs, along with examination of goat ribs subjected primarily to high kinetic energy stabs from an independent experiment, revealed consistent differences in damage patterns between the two conditions. In the case of Shanidar 3, the lack of major involvement of more than one rib, the lack of fracturing of the affected and adjacent ribs, and the lack of bony defects associated with the lesion (such as wastage, hinging, and radiating fracture lines) suggests that the weapon that wounded him was carrying relatively low kinetic energy. While accidental injury or attack with a thrusting spear or knife cannot absolutely be ruled out, the position, angulation, and morphology of the lesion is most consistent with injury by a low-mass, low-kinetic energy projectile weapon. Given the potential temporal overlap of Shanidar 3 with early modern humans in western Asia, and the possibility that the latter were armed with projectile weapon systems, this case carries more than simple paleoforensic interest.

Craniofacial Feminization, Social Tolerance, and the Origins of Behavioral Modernity

The past 200,000 years of human cultural evolution have witnessed the persistent establishment of behaviors involving innovation, planning depth, and abstract and symbolic thought, or what has been called “behavioral modernity.” Demographic models based on increased human population density from the late Pleistocene onward have been increasingly invoked to understand the emergence of behavioral modernity. However, high levels of social tolerance, as seen among living humans, are a necessary prerequisite to life at higher population densities and to the kinds of cooperative cultural behaviors essential to these demographic models. Here we provide data on craniofacial feminization (reduction in average brow ridge projection and shortening of the upper facial skeleton) in Homo sapiens from the Middle Pleistocene to recent times. We argue that temporal changes in human craniofacial morphology reflect reductions in average androgen reactivity (lower levels of adult circulating testosterone or reduced androgen receptor densities), which in turn reflect the evolution of enhanced social tolerance since the Middle Pleistocene.

Development of the curve of Spee

INTRODUCTION Ferdinand Graf von Spee is credited with characterizing human occlusal curvature viewed in the sagittal plane. This naturally occurring phenomenon has clinical importance in orthodontics and restorative dentistry, yet we have little understanding of when, how, or why it develops. The purpose of this study was to expand our understanding by examining the development of the curve of Spee longitudinally in a sample of untreated subjects with normal occlusion from the deciduous dentition to adulthood. METHODS Records of 16 male and 17 female subjects from the Iowa Facial Growth Study were selected and examined. The depth of the curve of Spee was measured on their study models at 7 time points from ages 4 (deciduous dentition) to 26 (adult dentition) years. The Wilcoxon signed rank test was used to compare changes in the curve of Spee depth between time points. For each subject, the relative eruption of the mandibular teeth was measured from corresponding cephalometric radiographs, and its contribution to the developing curve of Spee was ascertained. RESULTS In the deciduous dentition, the curve of Spee is minimal. At mean ages of 4.05 and 5.27 years, the average curve of Spee depths are 0.24 and 0.25 mm, respectively. With change to the transitional dentition, corresponding to the eruption of the mandibular permanent first molars and central incisors (mean age, 6.91 years), the curve of Spee depth increases significantly (P < 0.0001) to a mean maximum depth of 1.32 mm. The curve of Spee then remains essentially unchanged until eruption of the second molars (mean age, 12.38 years), when the depth increases (P < 0.0001) to a mean maximum depth of 2.17 mm. In the adolescent dentition (mean age, 16.21 years), the depth decreases slightly (P = 0.0009) to a mean maximum depth of 1.98 mm, and, in the adult dentition (mean age 26.98 years), the curve remains unchanged (P = 0.66), with a mean maximum depth of 2.02 mm. No significant differences in curve of Spee development were found between either the right and left sides of the mandibular arch or the sexes. Radiographic measurements of tooth eruption confirm that the greatest increases in the curve of Spee occur as the mandibular permanent incisors, first molars, or second molars erupt above the pre-existing occlusal plane. CONCLUSIONS On average, the curve of Spee initially develops as a result of mandibular permanent first molar and incisor eruption. The curve of Spee maintains this depth until the mandibular permanent second molars erupt above the occlusal plane, when it again deepens. During the adolescent dentition stage, the curve depth decreases slightly and then remains relatively stable into early adulthood.

When did the modern human pattern of childbirth arise? New insights from an old Neandertal pelvis

Human birthing is difficult owing to a tradeoff between large neonatal brain size and maternal pelvic dimensions, which are constrained by aspects of bipedal biomechanics (1, 2). The net effect is that human neonatal head size closely matches maternal pelvic dimensions, unlike in our closest living relatives, the great apes, whose pelvic dimensions are larger than neonatal head sizes. This size relationship, along with a twisted birth canal shape, makes human parturition mechanically difficult and results in a unique pattern of “rotational” birth (Fig. 1). As in humans, and unlike great apes, monkey neonatal head size closely matches the mothers pelvic dimensions. Although birth rotation occurs in some monkeys, the rotation pattern is different from that in modern humans, with monkey neonates exiting the birth canal facing forward (1). Therefore, in both apes and monkeys, it is relatively easy for a mother to guide her infant out of the birth canal, keep the umbilical cord from wrapping around the neck, and extract mucous from the nose and mouth to facilitate breathing. All of these critical activities are much more difficult for a human mother, whose infant emerges facing backwards, and pulling on the infant from this position also risks serious neck injury. For these reasons, humans uniquely engage in assisted birth (obligate midwifery). Although unassisted birth, the norm for nonhuman primates, does occasionally occur in humans, assisted birth and its myriad social implications are the human norm cross-culturally (1).

THE ROLE OF VERBAL INTERACTION DURING EXPERIMENTAL BIFACIAL STONE TOOL MANUFACTURE

Abstract Many researchers have hypothesized an analogous, and possibly evolutionary, relationship between Paleolithic stone tool manufacture and language. This study uses a unique design to investigate how spoken language may affect the transmission of learning to make stone tools and comes to surprising results that may have important implications for our views of this relationship. We conducted an experiment to test the effect of verbal communication on large core biface manufacture during the earliest stages of learning. Previously untrained flintknappers were assigned to two different communication conditions, one with and one without spoken language, and were instructed to replicate the bifaces produced by the same instructor. The attempted bifaces (total = 334) from the two groups were compared using an Elliptical Fourier analysis, the Flip Test, and a rating scale by an independent lithicist. We found no significant difference in the overall shape, symmetry, or other measures of skill among the two groups, using all three of these methods. Analysis of the 18,149 debitage elements from the experiment, however, revealed that the two groups set up their striking platforms in fundamentally different ways. The nonverbal group produced more efficient flakes than the verbal group, as evidenced by the significantly higher ratios of platform width to platform thickness and size to mass of the nonverbal subjects’ flakes. These results indicate that verbal interaction is not a necessary component of the transmission of the overall shape, form, and symmetry of a biface in modern human novice subjects, and it can hinder the progress of verbal learners because of their tendency to over-imitate actions of the instructor that exceed their current skill set.

Sutural growth restriction and modern human facial evolution: an experimental study in a pig model.

Facial size reduction and facial retraction are key features that distinguish modern humans from archaic Homo. In order to more fully understand the emergence of modern human craniofacial form, it is necessary to understand the underlying evolutionary basis for these defining characteristics. Although it is well established that the cranial base exerts considerable influence on the evolutionary and ontogenetic development of facial form, less emphasis has been placed on developmental factors intrinsic to the facial skeleton proper. The present analysis was designed to assess anteroposterior facial reduction in a pig model and to examine the potential role that this dynamic has played in the evolution of modern human facial form. Ten female sibship cohorts, each consisting of three individuals, were allocated to one of three groups. In the experimental group (n = 10), microplates were affixed bilaterally across the zygomaticomaxillary and frontonasomaxillary sutures at 2 months of age. The sham group (n = 10) received only screw implantation and the controls (n = 10) underwent no surgery. Following 4 months of post‐surgical growth, we assessed variation in facial form using linear measurements and principal components analysis of Procrustes scaled landmarks. There were no differences between the control and sham groups; however, the experimental group exhibited a highly significant reduction in facial projection and overall size. These changes were associated with significant differences in the infraorbital region of the experimental group including the presence of an infraorbital depression and an inferiorly and coronally oriented infraorbital plane in contrast to a flat, superiorly and sagittally infraorbital plane in the control and sham groups. These altered configurations are markedly similar to important additional facial features that differentiate modern humans from archaic Homo, and suggest that facial length restriction via rigid plate fixation is a potentially useful model to assess the developmental factors that underlie changing patterns in craniofacial form associated with the emergence of modern humans.