April 08, 2008

Geostatistics in biological anthropology of the Irish

American Journal of Physical Anthropology, Volume 136, Issue 1 , Pages 1 - 10

Geostatistics and spatial analysis in biological anthropology

John H. Relethford

Abstract A variety of methods have been used to make evolutionary inferences based on the spatial distribution of biological data, including reconstructing population history and detection of the geographic pattern of natural selection. This article provides an examination of geostatistical analysis, a method used widely in geology but which has not often been applied in biological anthropology. Geostatistical analysis begins with the examination of a variogram, a plot showing the relationship between a biological distance measure and the geographic distance between data points and which provides information on the extent and pattern of spatial correlation. The results of variogram analysis are used for interpolating values of unknown data points in order to construct a contour map, a process known as kriging. The methods of geostatistical analysis and discussion of potential problems are applied to a large data set of anthropometric measures for 197 populations in Ireland. The geostatistical analysis reveals two major sources of spatial variation. One pattern, seen for overall body and craniofacial size, shows an east-west cline most likely reflecting the combined effects of past population dispersal and settlement. The second pattern is seen for craniofacial height and shows an isolation by distance pattern reflecting rapid spatial changes in the midlands region of Ireland, perhaps attributable to the genetic impact of the Vikings. The correspondence of these results with other analyses of these data and the additional insights generated from variogram analysis and kriging illustrate the potential utility of geostatistical analysis in biological anthropology.


1 comment:

pconroy said...

If anyone has access to the article - please email it to me - thanks.

I grew up in the Irish Midlands, and historically my lastname (Conroy) has been linked to the Southern O'Neill (via the Dunne and Regan/Reagan names), but there is a competing history linking it to the Vikings.

Genetically, I am M222+, so am R1b1c7 (or now R1b1b2e, based on the new terminology), which seems to indicate O'Neill heritage.

However - like Ronald Reagan and Maggie Thatcher - my Dad has a certain genetic condition which causes the sinews in his hands to tighten - this has been linked to Viking heritage.

So is the difference in craniofacial height of the Midlands more or less than the Irish average??