• Claire Benjamin

Karen Sears: Looking at life's changes


When most five-year-olds dreamed of careers as superheroes and princesses, Karen Sears (GNDP) decided she wanted to be a paleoanthropologist.

“How life changes over time is something that has really always fascinated me,” said Sears, an Assistant Professor in the School of Integrative Biology. “I always knew that I would pursue some aspect of that.”

In graduate school, her adviser studied South American marsupial fossils from the Age of Mammals, an era that spans the past 66 million years. During this time, marsupial mammals have dominated South America while placental animals have dominated North and Central America.

“Why do we see that pattern? Why don't we see this pattern?” she asked herself. “Why is the world full of rats instead of opossums or these other forms? What is going on to shape the large scale patterns that we see?”

Sears realized that while paleontology could show how animals changed, she would need evolutionary developmental biology to explain why.

Today Sears combines her background in paleontology with her knowledge of genetics and development to study the processes that have shaped mammalian evolution.

“I feel like we are at the point in our lab right now where we can start bringing together all of these different fields, which historically have not been brought together,” Sears said. “Now we can look at the fossil record of mammals and study how their genes interact throughout their development to cause them to have different kinds of limbs. We are also trying to understand how this process of development might be biasing, shaping, and constraining these patterns of evolution.”

In the second episode of Your Inner Fish, a three-part PBS series that traces 350 million years of human evolution, Sears describes how two tiny bones disconnect from the jawbone, shrink, and move up to become middle ear bones as embryonic opossums mature into adults. She studies this developmental process to help her understand how mammals may have evolved middle ear bones from reptile jawbones.

In addition to opossums, Sears works with bats, pigs, horses, camels, and any other specimens that she can get her hands on. For her, getting specimens if often the limiting factor in her research on organ development, digit reduction, and other topics in evolutionary developmental biology.

In the past year alone, Sears has visited Puerto Rico, Belize, and Trinidad to collect bat specimens.

“You have those moments when you are sitting there in the moonlight with your net, collecting your bats, beside a Mayan temple and you think, ‘Wow. This is my life,’” she said. “This is what I get paid to do. It’s pretty amazing.”

Sears earned a bachelor’s degree in anthropology and zoology from the University of Wisconsin–Madison and a doctorate in evolutionary biology from the University of Chicago. She was a postdoctoral researcher with professor Lee Niswander at Memorial Sloan Kettering Cancer Center and later at the University of Colorado. Sears is married to Jon Marcot, a research assistant professor at Illinois, and they have two kids.

This profile originally appeared in the Institute for Genomic Biology's September 2014 newsletter.


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© Claire Benjamin