Human migration and evolution along the Indian Ocean Rim: genetics, morphometrics, and palaeoenvironment
The origin and early dispersal of our own species Homo sapiens is a key issue in human evolution. Although most scientists agree that humans evolved in Africa around 200ka, there is no consensus as to the route they took out of Africa to disperse throughout the rest of the Old World.
This project set out to examine evidence for a proposed 'Southern Route' out of Africa, following the coastal rim of the Indian Ocean, into southern Asia, and thence into South-East Asia, Indonesia, Australia and beyond.
It quantifies, compares and contrasts the genetic and morphological evolution of humans during these proposed migrations along the Indian Ocean rim in the late Pleistocene.
Four of our major findings
1. Researchers at the Universities of Durham and Oxford, and the Natural History Museum in London used a variety of resources to test the hypothesis that Homo sapiens evolved in Africa 200ka and dispersed to the rest of the Old World via this Southern Route.
Human populations today show significant variation in their genetic makeup and skeletal and dental morphology, which can be quantified and compared to gain an insight into their origin and relatedness.
By bringing together analyses of all these measures of variation, we were able to assess which one are most likely to reflect human evolutionary history; quantify the influence of environmental factors on human morphology; and describe the likely processes of evolution and dispersal that led to the population diversity we can observe today.
2. Project members from Durham University used three-dimensional metric data from nearly 2000 skeletons representing over 30 distinct human populations, to look at variability in skull shape along the entire Indian Ocean rim.
We concluded that although regional differentiation exists along this coastal route, local environmental factors such as temperature or rainfall are important causes of variation in human craniofacial morphology and are related to very specific structures in the human skull.
This suggests a complex interaction between genetic heritage, founder effect and dispersal history, in forming the patterns of craniofacial diversity that can be observed around the Indian Ocean rim today.
3. To put these differences into a genetic context, team members from Oxford University looked at the genetic makeup of these populations along the southern route, using ancient DNA from a subset of the skeletons from the Durham study.
With a focus on samples from the Andaman, Nicobar and Torres Strait Islands populations, as well as some from central Australia, they were able to illustrate the more specific aspects of the evolutionary relationships between these populations, and to develop more accurate ways of recovering and analysing DNA from skeletal museum samples.
4. At the Natural History Museum, work has largely focused on analyses of dental structures. These results will be put into context with the detailed analyses of the cranial and ancient DNA data.
This project demonstrated complex inter-actions between evolution, dispersal and environment in determining local morphologies and genotypes, as well as the relative importance of those factors in influencing skeletal and genetic variability.
We were able to do this because the power of new genetic and morphometric techniques allows different determinants of variation to be teased apart and studied in and out of a temporal context. We also showed the continuing scientific importance of skeletal archives in museums for reconstructing and understanding our past.
This summary was compiled by Una Strand Viðarsdóttir (Durham). Peter Holland (Oxford) is the PI for this project.
Una Strand Viðarsdóttir (Durham) and Chris Stringer (Natural History Museum, London).
Trudi Buck (Durham) and Phillip Endicott (Oxford).
Tim Compton (Natural History Museum, London).
For more information please contact Una Strand Viðarsdóttir.