Synchrotron Radiation Microtomography: A Tool for Paleontology
- P Tafforeau
- ESRF Newsletter
represented by only five genera: gibbons, orang-utans, gorillas, chimpanzees and our own species, Homo sapiens. In the Miocene period, between 20 and 6 million years (MY) ago, however, this was a much more diverse group, as demonstrated by the numerous (approximately 20) fossil genera that have been discovered in Africa, Asia and Europe. The most ancient hominoids lived around 20 million MY ago in Africa. Outside Africa, the first hominoids date from around 16.5 MY ago, but many different forms are known to have lived in Europe and Asia 12-6 MY ago. Subsequently, the group declined in diversity, probably due to climate changes. Several hypotheses have been suggested to explain the phylogenetic (evolutionary) relationships of the fossil and extant (modern) species and to describe their paleobiogeography – that is, their geographic migration and diversification. The traditional hypothesis is that Africa was the principal area of diversification during the whole Miocene period, with successive migrations to Europe and Asia followed by local evolution on all three continents (map A). Over the last few years, however, a new hypothesis has emerged. It also proposes that the hominoids originated in Africa, but that primitive forms then migrated towards Asia, and after a progressive extinction in Africa, Africa and Europe were repopulated by successive migrations from Asia (map B). According to this hypothesis, the principal area of hominoid diversification was Asia instead of Africa. The key fossils to test these two scenarios should therefore be found in Asia. In 2003, research in Thailand led to the discovery of a previously unknown species of fossil hominoid from approximately 12 MY ago (Chaimanee et al., 2003). About 20 isolated teeth (figure 1A), attributed to several male and female individuals, showed that this species was a large hominoid with a strong sexual dimorphism – the male was much larger than the female, with more developed canines. It was named cf. Lufengpithecus chiangmuanensis.