Web Exclusives: Systems
Modeling the Origin of Organisms
Sergey Gavrilets has come a long way from modeling photosynthesis at Moscow State University. Now he's developing models that explain the origin of multicellular organisms.
"The increase in biological complexity is a major transition in evolution, and there have been almost no mathematical theories of how it emerges," says Gavrilets, a theoretical biologist at the University of Tennessee, Knoxville.
An organism consists of specialized cells with distinct functions that collectively ensure survival and reproductive success. One of Gavrilets' simple and biologically realistic models shows how cells become dedicated to functions that are important either for survival or for reproduction. Using the model, Gavrilets found that the division of labor could occur relatively rapidly, depending on the mutation rate, number of cells and other factors. The theoretical results may also explain the social behavior of some insects and the inception of organs.
Beyond elucidating the genesis of biological complexity, Gavrilets is developing general models of other evolutionary events, such as the origin of different species and the division of parental responsibilities between the two sexes. Modeling allows scientists to infer how and when these major evolutionary processes took place, he says: "Mathematical models help biologists look at their data and see the bigger picture."
His computational crunching isn't just an intellectual activity—it has applications well beyond the lab. Gavrilets is working on models that can be used to predict the emergence of diseases. Biologists had thought that organisms had to be reproductively isolated to split into different species, but Gavrilets has found that certain pathogens don't have to be disconnected for distinct species to form. These findings may help scientists understand how pathogens are able to infect new hosts and spawn diseases. This kind of modeling, Gavrilets says, shows that "fundamental research not related to the immediate practical needs of society can lead to conclusions that are helpful in real-life applications."