Popular Science Presentation

The first four-legged animals, the so-called tetrapods, evolved almost 400 million years ago. They originated in the water, and their later adaptation to a life on land is considered one of the most important steps in the evolution of animals. Several other fish groups, such as mud crawlers and lungfish, have tried to colonize the country but have not succeeded in establishing themselves as successful land animals. The first tetrapods, however, eventually gave rise to thousands of species of amphibians, reptiles, birds and mammals - including ourselves. The adaptation of tetrapods to land is therefore an important research topic. Many researchers in geology, paleontology, and biology have focused on it for more than a century, but despite this, some consensus has emerged as to when or how the adaptation took place.

All events that affect an animal's growth leave traces in the growing bones, much like annual rings in a tree, and these traces are also preserved in fossils of early tetrapods. By studying the internal structure of the fossil bones, you can get a lot of information about the biology and life history of the tetrapods. With my colleague, Paul Tafforeau from the European synchrotron ESRF in France, we have developed new tomographic techniques, based on synchrotron radiation (a special and very powerful X-ray), which make it possible to image the three-dimensional internal microstructure of the irreplaceable fossil bones without damaging them . Using these, we will 1) determine when the fins were transformed into limbs, 2) how the limbs were adapted for walking on land, and 3) what environmental conditions drove the land adaptation of tetrapods.