Cataloging the diversity of life on Earth is challenging enough, but when scientists attempt to draw a phylogeny — the branching family tree of a group of species over their evolutionary history — the challenge goes from merely difficult to potentially impossible. The fossil record is the only direct evidence scientists have about the history of species diversity, but it can be full of holes or totally nonexistent, depending on the type of organisms. The only hope in such cases is to infer historical diversity from modern DNA sequences, but such techniques have a fatal flaw: the results they provide are demonstrably incorrect.
The Penn team has developed a new technique for analyzing phylogenies and shown that the results stand up against the known fossil history of whale species, a gold standard in terms of fossil records.
“We’ve put contemporary molecular approaches on equal footing with classical paleontological approaches,” said Joshua B. Plotkin of the Department of Biology in Penn’s School of Arts and Sciences and the Department of Computer and Information Science in the School of Engineering and Applied Science.