The Genome Writ Large

According to DeSalle, Novacek "led the charge" toward bringing molecular biology into the Museum, though Novacek points out that he was supported by several visionary curators, among them Niles Eldredge, who was already beginning to recruit molecular researchers for the invertebrate department. In 1990 the Museum opened its Molecular Systematics Laboratory, codirected by DeSalle and Ward C. Wheeler. A second molecular laboratory opened in 1995, headed by Joel Cracraft, of the ornithology department. This year, under the management of molecular biologist Bob Hanner, the Ambrose Monell Collection for Molecular and Microbial Research--a repository that will eventually hold 750,000 frozen samples of organic tissue and DNA from a host of species--begins operations.

Now, drawing on the breadth of its research in natural history, its laboratories, and its collections, the Museum is in a strong position to contribute to the field of molecular biology. It has, in fact, been catapulted into the forefront of a new molecular specialty called comparative genomics: the comparison of DNA throughout the animal kingdom.

One goal of comparative genomics is to identify which sequences of genes in the human genome are associated with which traits. "We take a DNA sequence from our genome and search for it in a mouse, a fruit fly, a worm, a nematode, and yeast--all of whose genomes have been either completely sequenced or nearly so. If we locate it in some of them and we identify its function, chances are that the function in the human genome is the same," DeSalle says. "The process is difficult, but it's where the really neat work is going to happen in the near future, and this is where I think the Museum comes in."

Another goal of comparative genomics is to plot evolutionary relationships. Evolution can be tracked back across the eons by comparing genomes and using as yardsticks the similarities and mutations of genes for the same traits in different species--whether the traits are a backbone, two eyes, or four legs. Using molecular biology as well as traditional morphology, Museum scientists can compare and contrast the evidence. The two approaches do not always agree. In the mammalogy department, for example, molecular research projects are causing fur to fly. Morphologists long thought that the primitive mammalian order Monotremata, which includes the platypus, branched off during the Cretaceous Period (between 140 and 70 million years ago). This would make the marsupial and placental mammals--thought to have branched off later--closely related. But molecular evidence now suggests that the marsupials and the monotremes branched off much earlier than the placentals did and that they are therefore the closer relatives.

Following the demise of the dinosaurs at the end of the Cretaceous, there occurred a great radiation--a "star burst," as Novacek calls it--of mammals, particularly of placentals, and molecular biology is proving a valuable and controversial tool in finding out what happened. Based on morphology, most mammalogists of the last century agreed that rabbits, for instance, are not closely related to rodents. Today molecular studies at the Museum suggest they are.