Hans Larsson is a fast walker and a fast talker. You need to be fit to keep up with him on the hills of the McGill University neighborhood in Montreal, let alone on the remote islands of the Canadian Arctic where he searches for fossils in summer fieldwork. He talks the way he walks, in a freely swinging fast-paced lope that ranges from the philosophy of science to genetic probes to the rich Cretaceous ecosystem he is exploring at another field site in Alberta.
Larsson is at the forefront of merging paleontology and molecular biology in an effort to connect major evolutionary changes—the development of new species and new characteristics, new shapes and structures, new kinds of animals—to changes in specific genes and in how those genes are regulated. He is interested in reactivating dormant genes or changing the regulation of active genes in embryos to bring back ancestral traits that have been lost in evolution.
Scientists can do this now because we have the fossils. We have the lessons of developmental biology. And we have the tools of molecular biology. All of these are being merged in the study of the history of life in evolutionary developmental biology, or evo devo.
Collecting and cataloging fossil bones, the heart of vertebrate paleontology, has been primarily a historical enterprise, one of unearthing ancient information and looking for patterns. Laboratory science has been conducted in a different fashion. You could suspect, say, that a gene that controls a particular growth factor is important in how five-fingered hands develop at the ends of arms. So the hypothesis might be that if that gene were absent or nonfunctional, the hand would not develop. You can engineer mice so that the gene is absent or silenced and see what happens to the development of the embryo. If the hand develops perfectly, your hypothesis is false. If the hand does not develop, you have good evidence that the gene in question does what you thought it did.
