Synchrotron Light Helps to Reconstitute Orang-utan Ancestor's Jaw

Fossil experts have recently discovered an hominoid in Thailand that could be the oldest known relative of present-day orang-utans. Thanks to synchrotron light at the ESRF¹, these researchers have been able to analyse 18 teeth of this hominoid that were found embedded in coal in Northern Thailand. They compared them with dental records from other ancient apes. The new species, named cf. Lufengpithecus chiangmuanensis, dates from around 12 million years ago (middle Miocene period) and is more closely related to the orang-utan than any previously found fossil. The technique of microtomography was the key tool for reconstructing a vertical section through different teeth to show the thickness of the enamel. It also allowed scientists to recreate a 3-D computer model of the jaws of a male and female fossil ape.

Microtomography² was used to reconstruct the structure of each tooth in three dimensions from a set of two-dimensional images, with a resolution of a few micrometres or less. After comparing the teeth with those of present-day orang-utans, the team found a lot of similarities. "We can never be sure if it's a direct ancestor, but it's something very close," explains Jean-Jacques Jaeger, Professor of Palaeontology at the University of Montpellier in France, and one of the team who made the find. This theory is confirmed by the fact that fossilised pollen was found with the teeth, showing that cf. Lufengpithecus chiangmuanensis once lived in a tropical forest, just like today orang-utans. The fossilised pollen bears a striking resemblance to pollen from present-day African flora, which leads us to believe that the same flora and fauna could be found in Eastern Africa and tropical Asia at that time.

Tentative three-dimensional reconstruction of the jaws of cf. Lufengpithecus chiangmuanensis. The different colours indicate the origins of the teeth:
- Grey for the discovered fossil teeth
- Pink for symmetric equivalents of these teeth
- Blue for teeth derived from the other sex after a size correction
- Green for teeth that we don’t have for either male or female.
They have been extrapolated from the other teeth by comparisons with fossil and existing hominoids. Picture by Paul Tafforeau, Institut des Sciences de l'Evolution de Montpellier (France), in collaboration with the ID19 beamline at the ESRF (please credit the picture).

For more information, please consult the Letter to Nature: Chaimanee, Y. et al., A Middle Miocene hominoid from Thailand and orangutan origins, Nature, 422, 61 - 65, (2003).

1. The European Synchrotron Radiation Facility (ESRF) is constituted as an international facility with 17 participating countries to operate, maintain and develop a synchrotron radiation source and associated instruments. It operates the most powerful third generation synchrotron radiation source in Europe (www.esrf.fr).
2. There are four beamlines at the ESRF using microtomography. This imaging technique is used in a wide range of research, such as, materials science, medical, geophysical, environmental or paleontological studies.