Quantifying the mosaic:
A Leverhulme Trust funded project - £222,700 over 2 years.
This exciting new project brings together archaeologists, palaeontologists and ecologists to examine a fundamental assumption in human evolution – that our ancestors lived in mosaic* habitats. From the very earliest hominin sites (~7.0 million years with Sahelanthropus in Chad) to modern Homo sapiens sites in East Africa, the palaeoenvironmental reconstructions are of mosaic habitats. Did our ancestors really prefer these habitats or do we reconstruct the environments as mosaics because we cannot refine the fossil record? Our project aims to find out, using satellite imagery of modern African landscapes to examine the scale at which landscapes become mosaics (fig. 1) and then to compare these scales to what we know of the archaeological record.
Fig 1. Above left: A schematic diagram of a mosaic habitat with bush, large trees, open grassland and water. Above right: Taung, a hominin site in South Africa - a landscape with trees, open water, bushland and variable topography including low cliffs and hills – is this a mosaic? (photo: Sally Reynolds.)
Key ideas to be tested are:
Mosaic habitat types are found throughout Africa. To be tested with stratified-random sampling of the continent using digital satellite imagery.
Mosaic habitats are found at differing spatial scales, from local to regional, to be tested using boxes of increasing size (Fig. 2)
There is a positive spatial correlation between modern mosaic habitats and the location of hominin sites, i.e. mosaics are more common along the East African Rift, and into areas of southern Africa.
Hominin sites are disproportionately identified as ‘mosaic’.
Fig. 2. The principle of applying boxes of different scales to the landscape. Above left: blank squares of increasing size, 0.5x0.5km, 1.0x1.0km and 2.0x2.0km. Middle: squares overlain on a diverse landscape. The inner square (0.5x0.5km) is largely forested with a few open patches, the larger square shows trees and open habitat, while the 2.0x2.0km square is a mosaic of grassland, forest and water. Right: boxes overlain on actual satellite image of the Kruger National Park, South Africa. At this scale individual trees can be identified, and proportions of canopy cover, water, etc., can be readily calculated (Image source: GoogleEarth).
For the quantification phase we will be using GIS (probably ArcGIS) to look at the frequency of mosaics in modern Africa. We will, of course, need to account for the effect of the Sahara and also large urban centres on our data collection, and we will modify strategies used in previous studies to achieve this.
If you would like to be involved in this project, we will shortly be advertising for a senior postdoctoral research assistant in Landscape Ecology – see the ‘people’ page for details. Experience in spatial analyses and quantification of satellite imagery is essential for this position.
Our project was featured on page 7 of the Leverhulme Trust newsletter in April 2012
* Mosaic - environments with a mix of surface water (i.e. rivers or lakes), river or lakeside forest, grassland and wooded savannah.