In year four, research by team member Charles Marshall focused on improving confidence intervals in paleontological estimates of evolutionary first and last appearances of taxa and on reconciling molecular clock and paleontological estimates of evolutionary divergence times. Research has also continued on the construction of a global database for the fossil record that will enable paleontologists to understand the history of biological diversity and facilitate the differentiation of the biological from geological signals in Phanerozoic marine diversity studies. In an important development, Marshall and his students have shown that the algorithm from which it was inferred that marine diversity hasn't increased since the Paleozoic fails to take beta-diversity into account.