A prominent American biologist, Joe Thornton is a professor at the University of Chicago and a former investigator at the Howard Hughes Medical Institute. He is renowned for his revolutionary work in ancestral gene resurrection and his exploration of the mechanisms through which proteins acquire new functions. His research has not only deepened our understanding of evolution but has also become a focal point in debates regarding intelligent design. Read more on ichicago.
Biography
Joe Thornton followed an unconventional path into the sciences. He began his academic journey as an English literature major and spent several years as an environmental activist with Greenpeace. This background gave him a unique perspective on the profound impact science has on both society and the environment.
Thornton eventually moved into formal biological training, earning his PhD in evolutionary genetics from Columbia University. His doctoral research on the mechanisms of genetic change laid the groundwork for his future in reconstructing molecular evolution. He later refined his expertise at the American Museum of Natural History, where he mastered techniques for tracing the evolutionary histories of proteins. It was during this period that he began merging his activist roots with empirical research on molecular evolution.
In 2002, Thornton launched his independent academic career as an assistant professor of biology at the University of Oregon. By 2009, he had risen to the rank of professor at the Center for Ecology and Evolutionary Biology. In 2012, he joined the University of Chicago, where he currently leads the Thornton Lab and contributes to interdisciplinary graduate programs in ecology, evolution, and genetics.
Thornton’s work has been supported by the Howard Hughes Medical Institute, where he served as an Early Career Scientist, securing funding to study protein evolution through the resurrection of ancient genes. In 2014, he was awarded a John Simon Guggenheim Memorial Foundation Fellowship for his significant contributions to integrative evolutionary and molecular biology.
Research
Modern biology relies heavily on an interdisciplinary approach to understand how proteins evolve. Labs dedicated to these processes bring together evolutionary biologists, biochemists, biophysicists, computational biologists, and geneticists. By sharing methods and insights, researchers can peer deep into protein history to determine how their properties and functions have shifted over millions of years.
The primary tool in this research is phylogenetic reconstruction. Scientists “resurrect” protein sequences from the distant past, synthesize them in a laboratory, and then experimentally evaluate their biological functions and physical traits. This allows them to identify which mutations drove significant functional changes and how the interaction between different shifts—known as epistasis—shapes evolutionary outcomes.
Studying protein evolution helps answer both classic and contemporary questions: How do complex molecular systems emerge? Does evolution happen through small tweaks or major leaps? Does epistasis dictate specific evolutionary paths? Crucially, researchers also explore whether the evolutionary process is reversible and how biological architecture influences development. This analysis reveals why proteins possess specific structures and why some are more vulnerable to certain drugs or pollutants.
Thornton famously resurrected ancient steroid receptors to discover how they developed their specificity. His team reconstructed receptors dating back 450 to 600 million years, showing that the original versions were “promiscuous”—meaning they could interact with multiple ligands. Gradual, stabilizing mutations allowed modern receptors to develop precise specificity without losing their primary function. Laboratory tests proved that “winding back the clock” to ancestral states was impossible due to accumulated structural constraints, confirming the importance of historical contingency in defining modern protein functions.
Scientific Impact
Joe Thornton’s primary focus is ancestral protein resurrection. This technique allows him to reconstruct genetic sequences and recreate their activity in a lab setting to observe how proteins evolved new functions over eons. His work has significantly impacted discussions on biological complexity, as his experiments prove that complex functions can emerge through gradual evolutionary changes.
This highlights the roles of chance and contingency, making evolution both unpredictable and scientifically verifiable. His research has fostered the growth of experimental molecular paleobiology and provided mechanistic explanations for evolutionary processes, effectively dismantling arguments regarding the “irreducible complexity” of protein systems.
Thornton’s hallmark method is Ancestral Sequence Reconstruction (ASR). By using phylogenetic analysis of modern homologs, he recreates protein sequences that existed hundreds of millions of years ago. These proteins are then synthesized and analyzed for their biophysical properties. This approach reveals how evolutionary innovations arise through successive mutations that temporarily lift constraints, opening doors for further change. His methodology has since been adopted by labs worldwide to study ancient enzymes.
Thornton’s research is a staple in high-impact journals like Nature and Science, with over 14,500 citations. His work demonstrates how scientific methods can reconstruct the past and test hypotheses about the development of complex life, offering vital insights for biomedicine, genetics, and fundamental life sciences.
Awards and Honors
For his contributions to science, Joe Thornton has received numerous accolades, including the Presidential Early Career Award for Scientists and Engineers (PECASE) at the White House. He is also a recipient of the National Science Foundation (NSF) CAREER Award and the Howard Hughes Medical Institute Early Career Scientist Award. His unique approach—blending molecular biology with evolutionary theory—has established him as one of the leading scientists of our time.
His career serves as a powerful example of how an unconventional path—from English literature and environmental activism to molecular biology—can lead to revolutionary discoveries. He continues to inspire young scientists to embrace diverse interests and forge their own unique trails in the scientific world.