Research on the nature and timing of the Cambrian radiation

Lieberman has used phylogenetic biogeographic approaches to determine the relationship between earth history change and evolution and also to reconstruct the sequence of Paleozoic tectonic events. One of the time intervals his research has focused on is the Cambrian radiation: that key episode in the history of life when diverse, abundant animal remains appear in the fossil record. He has conducted phylogenetic analyses of the diverse olenelline trilobites and used these to study evolutionary and biogeographic patterns during the radiation.

Phylogenetic and biogeographic patterns suggest that the radiation of trilobites may have been underway in the late Neoproterozoic before the group becomes manifest in the fossil record; these patterns also suggest that the breakup of a supercontinent at the end of the Neoproterozoic had an important effect on the topology of the Cambrian radiation. He has also used probabilistic models to study how fast the rates of evolution were during this interval and the results suggest that rates of evolution were high at the time but not so high that new rules of evolution need to be invoked to explain the Cambrian radiation.

This research has been supported by the National Science Foundation and the National Geographic Society and has involved fieldwork in the Mackenzie Mountains, Northwest Territories, Canada.