A study to estimate the cranial capacity in 100 dry human skull bones

Background: Craniometry is the scientific measurement of the skull useful for anthropometry and forensic practice. Cranial index variations between and within population have been attributed to a complex interaction between genetic and environmental factors. The morphometric and non-morphometric studies of human skulls are very helpful for identification of the sex and age by anthropologist and forensic practice. Cranial dimensions and Cranial indices are considered as simplest and most efficient way to indicate facial differences. Materials and Methods: The present study will constitute 100 dried adult skulls belonging to both sexes available in the department of anatomy and forensic medicine RRMC and H, MS Ramaiah medical college and Sapthagiri medical college, Bangalore. Results: The mean cranial index of the skulls were 76.989 which classifies them under mesocephalic type and we find a significant correlation between the cranial index and the length height and breadth height index with the p value coming below 0.001. Conclusion: The mean, SD of all the parameters to calculate is mentioned in table 1. The mean cranial index is 76.989 with the standard deviation of 5.8775, that of length height index was 76.991 with SD of 4.4615 And that of breadth height index was 100.268 with SD of 5.4350. There is a significant correlation between the cranial index, the length height and breadth height indices. With a correlation value of 0.681 for length height index and -0.635 for breadth height index. Both had a p value <0.001.

Assessment of Gender Dimorphism Using Cephalometry in Iranian Population

Cephalic indices is useful for evaluating racial and gender differences. In this study, we aimed to asses Gender Dimorphism Using cephalometry in the Iranian Population. Different variables like cranial length (CL), cranial width (CW), and cranial height (CH) were measured and cranial index (CI), cranial capacity (CC), and brain weight of 400 Iranian volunteers were calculated. Data were analyzed by means of SPSS 22.0. There were significant differences in the mean value of all nasofacial parameters (P<0.05). The highest sensitivity and specificity to predict the gender dimorphism were related to FL and FW (0.990 and 0.97) and (0.970 and 0.94), respectively. Considering the differences between male and female cranial structures, can be useful in forensic medicine and designing neurosurgical and ergonomic instruments in addition, to distinguish and discover the gender of the humans related to the many years ago.

Selection for increased cranial capacity in small mammals during a century of urbanization

Urbanization is a selective force that is known to drive changes in the population dynamics of wildlife. How animals adapt to changing environmental conditions is crucial to their survival in these environments. Relative brain size, or cranial capacity, is a known proxy of behavioral flexibility, and can be used to assess how well a species has adapted to a particular environment. We examined changes in cranial capacity in a time series of small mammal skulls collected from urban and rural populations in southwestern Pennsylvania. Skulls from urban populations were collected from Allegheny County, an area that experienced rapid urbanization over the past century, and skulls of rural populations from the Powdermill Nature Reserve of the Carnegie Museum, which has remained relatively unchanged forest over the same period. Our results show that Peromyscus leucopus and Microtus pennsylvanicus from urban populations had significantly greater cranial capacity than their rural counterparts, but the opposite was true for Eptesicus fuscus. We found no difference in relative cranial capacity across time in any of the small mammal species. Our results suggest that a larger cranial capacity is selected for in an urban environment and reinforces the hypothesis that behavioral flexibility is important for animals to adapt to novel environments.

Revised estimates of Taung’s brain size growth

Cranial capacity, a proxy for the volume of the brain and associated cranial contents, is an important yardstick used to compare early hominin species because increasing brain size is a key characteristic of our lineage. In 1925, Raymond Dart claimed that a natural endocast found at the Buxton Limeworks near Taung, South Africa (which he named Australopithecus africanus), showed signs of neural reorganisation, but its juvenile status complicated comparison to other hominoid species. In an attempt to put its brain size and reorganisation into a comparative context, subsequent researchers have tried to estimate Taung’s adult cranial capacity by comparison to coarse-grained hominoid growth data. In this study, we simulated brain growth in A. africanus using asymptotic growth models in known-age mountain gorillas, chimpanzees and modern humans, and show that, at just under 4 years old, Taung’s brain had already finished or nearly finished growing according to hominoid developmental schedules. Percentage-growth remaining estimates are lower here than in previous studies using cross-sectional ontogenetic samples of unknown chronological age. Our new adult estimates (between 404 cm3 and 430 cm3 overall and 405–406 cm3 for chimpanzee models) are smaller than previous estimates with a ‘starting’ cranial capacity of 404 cm3, supporting the hypothesis that Taung’s adult brain size would have fallen toward the lower end of the A. africanus range of variation and strengthening the case that Taung was female.

‘Polynesians’ in the Brazilian hinterland? Sociohistorical perspectives on skulls, genomics, identity, and nationhood

In 1876, Brazilian physical anthropologists De Lacerda and Peixoto published findings of detailed anatomical and osteometric investigation of the new human skull collection of Rio de Janeiro’s Museu Nacional. They argued not only that the Indigenous ‘Botocudo’ in Brazil might be autochthonous to the New World, but also that they shared analogic proximity to other geographically very distant human groups – the New Caledonians and Australians – equally attributed limited cranial capacity and resultant inferior intellect. Described by Blumenbach and Morton, ‘Botocudo’ skulls were highly valued scientific specimens in 19th-century physical anthropology. A recent genomic study has again related ‘the Botocudo’ to Indigenous populations from the other side of the world by identifying ‘Polynesian ancestry’ in two of 14 Botocudo skulls held at the Museu Nacional. This article places the production of scientific knowledge in multidisciplinary, multiregional historical perspectives. We contextualize modern narratives in the biological sciences relating ‘Botocudo’ skulls and other cranial material from lowland South America to Polynesia, Melanesia, and Australia. With disturbing irony, such studies often unthinkingly reinscribe essentialized historic racial categories such as ‘the Botocudos’, ‘the Polynesians’, and ‘the Australo-Melanesians’. We conclude that the fertile alliance of intersecting sciences that is revolutionizing understandings of deep human pasts must be informed by sensitivity to the deep histories of terms, classification schemes, and the disciplines themselves.

Testing for correlation between traits under directional evolution

Being confounding factors, directional trends are likely to make two quantitative traits appear as spuriously correlated. By determining the probability distributions of independent contrasts when traits evolve following Brownian motions with linear trends, we show that the standard independent contrasts can not be used to test for correlation in this situation. We propose a multiple regression approach which corrects the bias caused by directional evolution.We show that our approach is equivalent to performing a Phylogenetic Generalized Least Squares (PGLS) analysis with tip times as covariables by providing a new and more general proof of the equivalence between PGLS and independent contrasts methods.Our approach is assessed and compared with three previous correlation tests on data simulated in various situations and overall outperforms all the other methods. The approach is next illustrated on a real dataset to test for correlation between hominin cranial capacity and body mass.