Metric Variation on Neurocranium among Some Ancient and Contemporary Human Populations (Adult Males) of Indian Sub- Continent

Introduction

Form and shape of human as well as primate skulls are studied by various cut off measurements. A species can be determined by its smaller and larger shape of skull by the craniometric measurements. Skull is the upper most part of our skeleton containing of head and face. The lower part of the facial skeleton is constituted by a single loose bone, the mandible. The skeleton of a skull without mandible is called cranium. The brain box, i.e., the neurocranium, is also designated as calvarium; and the topmost part of the skull i.e., the skull cap is designated as calotte [1]. The neurocranium is the part of the skull that bounds the cranial cavity, which contains the brain, and is made up of the ethmoid, frontal, parietal, occipital, sphenoid, and temporal bones [2].

The neurocranium is the portion of the skull that houses and protects the brain. It consists of several bones, including the frontal, parietal, temporal, occipital, and sphenoid bones. The features of the neurocranium in ancient populations can provide insights into their anatomy, health, and lifestyle [3].

It is rather difficult to assess the inter-group relationships by utilizing data based on sample univariate populations. We face the problem of biological taxonomy in this case. To understand such problem multivariate statistical analysis is necessary. To classify the populations and to find out their relationship we have to see the morphological affinities and differences between and among groups.

Hollo, et al. [4] are of the opinion that linear measurements of the neurocranium are better indicators of population differences than those of the facial skeleton. They analyzed six neurocranial and seven facial measurements. The neurocranium showed significant differences in seven cases between non subsequent periods and in one case, between two subsequent populations. They found no significant result for the facial skeleton. According to them neurocranium is a more conservative region and that population differences can be pointed out better in the neurocranium than in the facial skeleton.

Anthropological Survey of India, Kolkata has had diverse skeletal remains in possession. The skeletal remains are of ancient as well as contemporary period. These are one of the important subject matters of the present bio-anthropological investigation. This study deals with the metric variation on neurocranium amongst human populations of Indian Sub- Continent.

Material and Methods

This work was done at the paleoanthropology laboratory of Anthropological Survey of India, Kolkata on dry skulls. Four length measurements (maximum cranial length, glabella inion length, nasion inion length and glabella lambda length) and four breadth measurements (maximum cranial breadth, maximum frontal breadth, minimum frontal breadth and bi- auricular breadth) on neurocranium were recorded among the adult males of the respective population groups. The craniometric measurements were recorded placing the skull on a craniophore. An index (cranial index) was calculated involving maximum cranial length and maximum cranial breadth. The measurements were taken with the help of sliding and spreading caliper following Mukherje, et al. [1].

Dry skulls of four populations were studied. These are: Harappa, Kumhar Tekri, Contai and 24 Parganas.

Results

Means and standard deviation values of 9 neurocranium measurements (four length measurements, four breadth measurements and one index) among four groups of adult males were set out in Table 1. Highest value of maximum cranial length, glabella inion length, nasion inion length, glabella lambda length and minimum frontal breadth were recorded in Harappa and its lowest values were recorded in Contai skull. In case of other measurements, a different trend is noticed. In Table 2 means in terms of pooled standard deviation unit were furnished.

Size and shape distance values between any two groups were shown in Tables 3 and 4 respectively. This has been done for an overview on the size and shape factors used to find out the divergence among groups. Computed mean values for size and shape distance between 6 pairs were 1.14 and 1.92 respectively. This implies that the four population groups show a tendency to differ more in shape distance than size distance. Thus, here, the shape distance played a more important role than the size distance because of the morphological dissimilarity and differences.

On the basis of size and shape factors D2P values were calculated among 4 population groups. This was done to see the position of intra and inter-cluster average among the groups. The D2P values were furnished in Table 5. Following the methodology of Mardia, et al. [9] a dendrogram was computed (Figure 2) on the basis of the data given in Table 5. It appears that there is one distinct cluster formed by the Contai and 24 Parganas population group. The Kumhar Tekri maintains a higher distance with this cluster but the Harappa was found to be maintaining far distance with this cluster.

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Discussion

This study deals with length and breadth measurements of neurocranium characteristics of four population groups. Cranial index was calculated. While Harappa, Kumhar Tekri and 24 Parganas skull were mainly orthocranial, Contai skull was mainly hypsicranial. On the basis of eight measurements and one index, size and shape distance values were calculated between any two groups. This has been done for an overview on the size and shape factors used to find out the divergence among groups. Computed mean values for size and shape distance between 6 pairs were 1.14 and 1.92 respectively.

This implies that the four population groups show a tendency to differ more in shape distance than size distance. Thus, here, the shape distance played a more important role than the size distance because of the morphological dissimilarity and differences.

It is interesting to note that among these four population groups two are of ancient origin (the Harappa and Kumhar Tekri) and rest two (Contai, 24 Parganas) are of contemporary origin. It can be noted further that Harappa skulls are belonged to Bronze Age. A time span of 2300 to 1750 BC for this culture was obtained from radiocarbon dating. Whereas, origin of the Kumhar Tekri is less ancient than the Harappa. Its cultural affiliation is Early Historic. Dating of this specimen was 2nd to 3rd century BC.

To see the position of intra and inter-cluster average among 4 groups D2P values were calculated and Dendrogram was computed on the basis of D2P values. It appears from the analysis of dendrogram that there is one distinct cluster formed by the Contai and 24 Parganas population group. Though the Kumhar Tekri maintains a higher distance with this cluster but the Harappa was found to be maintaining far distance with this cluster. Thus, this study is indicative of interesting corroboration between neurocranium characteristics and inter-group relationships.

Conclusion

In the process of evolution ancient and contemporary skeleton show marked variation in different measurements. It is difficult to assess the inter-group relationships by utilizing data based on sample univariate populations. Problem of biological taxonomy generally appears in this case. To overcome such problem multivariate statistical analysis is useful. In this study neurocranium characteristics of four population groups from Indian Sub-Continent were dealt with the help of multivariate distance. As expected among four populations two contemporary populations form a cluster on the basis of D2P values, while other two ancient populations maintain distant relation with the contemporary population. As Harappa is more ancient than the Kumhar Tekri they maintain a far distant relation with Kumhar Tekri as well as other two contemporary populations.