Biomedical subjects

Philipp Gunz

Publications and source records attributed to Philipp Gunz.

9 recordsLinked to original sources

PubMed2006

The Neanderthal "chignon": variation, integration, and homology.

The occipital bun ("chignon") is cited widely as a Neanderthal derived trait. It encompasses the posterior projection/convexity of the occipital squama and is associated with lambdoid flattening on the parietal. A 'hemibun' in some Upper Paleolithic Europeans is thought by some authors to indicate interbreeding between Neanderthals and early modern Europeans. However, 'bunning' is difficult to measure, and the term has been applied to a range of morphological patterns. Furthermore, its usefulness in phylogenetic reconstruction and its homologous status across modern and fossil humans have been disputed. We present a geometric morphometric study that quantitatively evaluates the chignon, assesses its usefulness in separating Neanderthals from modern humans, and its degree of similarity to Upper Paleolithic 'hemibuns.' We measured the three-dimensional coordinates of closely spaced points along the midsagittal plane from bregma to inion and of anatomical landmarks in a large series of recent human crania and several Middle and Late Pleistocene European and African fossils. These coordinate data were processed using the techniques of geometric morphometrics and analyzed with relative warps, canonical variates, and singular warps. Our results show no separation between Neanderthals and modern humans, including early modern Europeans, when the shape of the occipital plane midsagittal-profile is considered alone. On the other hand, Neanderthals are well separated from both recent and fossil modern humans when information about the occipital's relative position and relative size are also included. Furthermore, the occurrence of a highly convex and posteriorly projecting midline occipital profile (interpreted as the occipital bun) is highly correlated (>0.8) with a flat parietal midsagittal profile and with antero-superiorly positioned temporal bones across both our recent and our fossil human samples. We conclude that the shape of the occipital profile alone should not be considered an independent trait, as it is very tightly integrated with braincase shape. Our analysis does not support differences in integration of the posterior midsagittal profile and the cranial base in Pleistocene and recent humans.

Animals↗

PubMed2006

Dental arch asymmetry in an isolated Adriatic community.

Developmental stability reflects the ability of a genotype to develop in the same way under varying environmental conditions. Deviations from developmental stability, arising from disruptive effects of environmental and genetic stresses, can be measured in terms of fluctuating asymmetry, a particularly sensitive indicator of the ability to cope with these stresses during ontogeny. In an inbred Adriatic island population, we expected dental arch fluctuating asymmetry 1) to be higher than in an outbred sample from the same island, and 2) within this population, to increase with the level of inbreeding. Due to environmental stress, we also expected to find higher fluctuating asymmetry in the outbred island population than in an urban reference group from the same country. The material consisted of 506 dental casts of 253 children from 1) the island of Hvar, and 2) Zagreb, Croatia. Three-dimensional coordinates of 26 landmarks spanning the arches were digitized. The analysis partitioned the asymmetry of arch forms into components for directional and fluctuating bilateral asymmetry, using the appropriate Procrustes method (geometric morphometrics). The results corroborated the hypotheses. Fluctuating asymmetry was found to be higher on the island than in Zagreb in all groups and in both jaws, and increased significantly with endogamy level in the lower jaw. There was no significant directional asymmetry in the Zagreb sample and likewise none in the upper jaws of the outbred island group, but significant directional asymmetry in both jaws of the inbred population and also in the lower jaws of the outbred island group. These results suggest an environmental as well as a genetic influence on dental arch asymmetry. Although the lower jaws expressed these two stresses almost additively, the upper jaws appeared to be better buffered. The role of directional asymmetry as a potential indicator of craniofacial developmental instability clearly merits further attention.

Adolescent↗

PubMed2005

Second to fourth digit ratio and face shape.

The average human male face differs from the average female face in size and shape of the jaws, cheek-bones, lips, eyes and nose. It is possible that this dimorphism is determined by sex steroids such as testosterone (T) and oestrogen (E), and several studies on the perception of such characteristics have been based on this assumption, but those studies focussed mainly on the relationship of male faces with circulating hormone levels; the corresponding biology of the female face remains mainly speculative. This paper is concerned with the relative importance of prenatal T and E levels (assessed via the 2D : 4D finger length ratio, a proxy for the ratio of T/E) and sex in the determination of facial form as characterized by 64 landmark points on facial photographs of 106 Austrians of college age. We found that (i) prenatal sex steroid ratios (in terms of 2D : 4D) and actual chromosomal sex dimorphism operate differently on faces, (ii) 2D : 4D affects male and female face shape by similar patterns, but (iii) is three times more intense in men than in women. There was no evidence that these effects were confounded by allometry or facial asymmetry. Our results suggest that studies on the perception of facial characteristics need to consider differential effects of prenatal hormone exposure and actual chromosomal gender in order to understand how characteristics have come to be rated 'masculine' or 'feminine' and the consequences of these perceptions in terms of mate preferences.

Adult↗

PubMed2004

Comparison of cranial ontogenetic trajectories among great apes and humans.

Molecular data suggest that humans are more closely related to chimpanzees than either is to the gorillas, yet one finds the closest similarity in craniofacial morphology to be among the great apes to the exclusion of humans. To clarify how and when these differences arise in ontogeny, we studied ontogenetic trajectories for Homo sapiens, Pan paniscus, Pan troglodytes, Gorilla gorilla and Pongo pygmaeus. A total of 96 traditional three-dimensional landmarks and semilandmarks on the face and cranial base were collected on 268 adult and sub-adult crania for a geometric morphometric analysis. The ontogenetic trajectories are compared by various techniques, including a new method, relative warps in size-shape space. We find that adult Homo sapiens specimens are clearly separated from the great apes in shape space and size-shape space. Around birth, Homo sapiens infants are already markedly different from the great apes, which overlap at this age but diverge among themselves postnatally. The results suggest that the small genetic differences between Homo and Pan affect early human ontogeny to induce the distinct adult human craniofacial morphology. Pure heterochrony does not sufficiently explain the human craniofacial morphology nor the differences among the African apes.

Adult↗

PubMed2004

Craniofacial sexual dimorphism patterns and allometry among extant hominids.

Craniofacial sexual dimorphism in primates varies in both magnitude and pattern among species. In the past two decades, there has been an increasing emphasis in exploring the correlations of these patterns with taxonomy and the variation in patterns within and among the craniofacial regions. Scrutinising these relationships for hominids, we decompose the craniofacial morphology in five taxa: Homo sapiens, Pan paniscus, Pan troglodytes, Gorilla gorilla and Pongo pygmaeus. 3D coordinates of 35 traditional landmarks and 61 semilandmarks, covering five ridge curves, are measured for each of 268 adult and sub-adult specimens and analysed using geometric morphometric methods. A multivariate analysis in size-shape space shows that ontogenetic scaling contributes to the development of sexual dimorphism in all five taxa, but to a varying extent. In absolute as well as in relative terms P. pygmaeus shows the greatest allometric component, followed by G. gorilla. Homo is intermediate, while in Pan the non-allometric constituent part contributes a large fraction to the actual sexual dimorphism, most markedly in the pygmy chimpanzee. An eigendecomposition of the five vectors of sexual dimorphism reveals two dimensions independent of allometry. One separates orang-utan sexual dimorphism from the African apes and Homo, and the other differentiates between the great apes and Homo with Pan mediating. We discuss these patterns and speculate on their use as characters for taxonomic analysis in the fossil record.

Animals↗

PubMed2004

Three-dimensional digital imaging of the partial Australopithecus africanus endocranium MLD 37/38.

OBJECTIVE: MLD 37/38 is one of a handful of Australopithecus africanus specimens. The partial cranium (about 2.5 million years old) is filled with stone matrix. The frontal part of the endocranium and most of the face are missing. Based on medical imaging techniques (computed tomography), we aimed to create virtual 3-dimensional reconstructions separately for the ectocranium and endocranium, reconstruct missing parts based on intraspecific comparison, estimate the endocranial capacity and describe endocranial morphological details that were physically inaccessible before. METHODS: We mapped fossilized bone as distinct from stone matrix for every slice of the computed tomographic image, creating virtual endocasts. The missing endocranial parts were reconstructed, using thin-plate spline warping, from a reference specimen (STS 5, a complete A. africanus cranium). In contrast with previous studies, a large number of landmarks (8 anatomical and 455 semi-landmarks) were used for this reproducible reconstruction. RESULTS: The endocranial capacity of the original partial cranium is 382 cm3, and the estimated volume for the reconstructed braincase is 440 cm3. On the left side of the endocast, signs of the meningeal vessel system could be detected. Transverse and sigmoid venous sinuses are present in MLD 37/38, whereas an occipital-marginal sinus system could not be found. CONCLUSIONS: The reconstructed endocranial capacity of MLD 37/38 lies within the range of other A. africanus specimens (428-515 cm3). In its dimensions, the endocast is similar to that of STS 5. The patterning of detected meningeal arterial branches resembles that of modern humans. The absence of an enlarged occipital-marginal sinus system is typical of A. africanus.

Animals↗

PubMed2004

Anthropology takes control of morphometrics.

There has been a startling change over the last decade in the intellectual context of morphometrics. In the 1990's, this field, which has not altered its focus upon the quantitative analysis of biomedical shape variation and shape change, was principally centered around concerns of medical image analysis; but now it is driven mainly by the demands of researchers in human variability, physical anthropology, primatology, and paleoanthropology instead. This essay celebrates that change and tries to account for it by reference to cognitive and intellectual aspects of the new home.

Animals↗

PubMed2003

Cranial integration in Homo: singular warps analysis of the midsagittal plane in ontogeny and evolution.

This study addresses some enduring issues of ontogenetic and evolutionary integration in the form of the hominid cranium. Our sample consists of 38 crania: 20 modern adult Homo sapiens, 14 sub-adult H. sapiens, and four archaic Homo. All specimens were CT-scanned except for two infant H. sapiens, who were imaged by MR instead. For each specimen 84 landmarks and semi-landmarks were located on the midsagittal plane and converted to Procrustes shape coordinates. Integration was quantified by the method of singular warps, a new geometric-statistical approach to visualizing correlations among regions. The two classic patterns of integration, evolutionary and ontogenetic, were jointly explored by comparing analyses of overlapping subsamples that span ranges of different hypothetical factors. Evolutionary integration is expressed in the subsample of 24 adult Homo, and ontogenetic integration in the subsample of 34 H. sapiens. In this data set, vault, cranial base, and face show striking and localized patterns of covariation over ontogeny, similar but not identical to the patterns seen over evolution. The principal differences between ontogeny and phylogeny pertain to the cranial base. There is also a component of cranial length to height ratio not reducible to either process. Our methodology allows a separation of these independent processes (and their impact on cranial shape) that conventional methods have not found.

Adult↗

PubMedDate not supplied

Heterochrony and geometric morphometrics: a comparison of cranial growth in Pan paniscus versus Pan troglodytes.

Heterochrony, the classic framework in which to study ontogeny and phylogeny, in essence relies on a univariate concept of shape. Though principal component (PC) plots of multivariate shape data seem to resemble classical bivariate allometric plots, the language of heterochrony cannot be translated directly into general multivariate methodology. We simulate idealized multivariate ontogenetic trajectories and explore their appearance in PC plots of shape space and size-shape space. Only if the trajectories of two related species lie along exactly the same path in shape space can the classic terminology of heterochrony apply and pure dissociation of size change against shape change be detected. Regional heterochrony--the variation of apparent heterochrony by region--implies a dissociation of local growth fields and cannot be identified in an overall PC analysis. We exemplify a geometric morphometric approach to these issues using adult and subadult crania of 48 Pan paniscus and 47 Pan troglodytes specimens. On each specimen, we digitized 47 landmarks and 144 semilandmarks on facial curves and the external neurocranial surface. We reject the hypothesis of global heterochrony in the cranium of Pan as well as regional heterochrony for the lower face, the upper face, and the neurocranium.

Aging↗