To many, Charles Darwin’s finches are the quintessential symbol of evolutionary theory. To Scott Steppan, the mouse is a much more compelling example.

Considering that mice and rats have thrived just about everywhere and become the most successful mammals on the planet, he has a point.

But piecing together their family history has been an intractable puzzle. For decades, biologists compared shapes, colors, bones and teeth to reconstruct family trees. Beak shape shored up Darwin’s theory of natural selection. But, especially in the enormous group of mice and rats, looks often deceive when it comes to defining familial ties. Distant cousins on the tree can look more alike than some sister species.

“It’s the bugaboo of phylogenetics,” Steppan said.

Now, with DNA technology, he goes beyond appearances to draw comparisons at the gene level and bring into focus hazy histories and relationships. Throw in the power and speed of the latest computers, and Steppan shows that reconstructing the mouse family tree is not as daunting as it once seemed.

Last year, he published the most comprehensive, defensible version of the mouse tree. Where questions remain, Steppan is honing in.

For practical purposes, his research can be applied to the study of human diseases, such as the deadly hantavirus that is carried by deer mice.

But what Steppan finds the most exhilarating about evolution is that it ultimately leads to the study of life at its most basic level.

“Seeing where all this diversity came from is a fundamentally fascinating question,” he said.

Because of the advances in computers, scientists may reach an answer faster than anyone imagined just 20 years ago.

“It’s a total revolution in the field of systematics,” Steppan said.

Scott Steppan (Ph.D., University of Chicago) collaborates with scientists around the world to piece together the enormous family history of mice and rats. A recognized authority in this area, Steppan also is a contributor to the international Tree of Life project, which is tackling the family tree of all life on the planet back to its most primitive ancestors.