Two Mutations Triggered An Evolutionary Leap 500 Million Years Ago


Two key mutations 500 million years ago set the stage for how our hormonal and reproductive systems function today.

Joe Thornton, PhD, professor of human genetics and ecology & evolution at the University of Chicago, and a team of researchers from the University of Oregon, Emory University and the Scripps Research Institute, used a “molecular time travel” method to reverse engineer the genetic structures of ancient protein receptors. As they worked their way back up the tree of life to modern DNA, they traced how the ancestor of the entire receptor family — which recognized only estrogens — evolved into descendant proteins capable of recognizing other steroid hormones, such as testosterone, progesterone and the stress hormone cortisol.

Joe Thornton, PhD

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“Changes in just two letters of the genetic code in our deep evolutionary past caused a massive shift in the function of one protein and set in motion the evolution of our present-day hormonal and reproductive systems,” said Joe Thornton, PhD, professor of human genetics and ecology & evolution at the University of Chicago, who led the study.

“If those two mutations had not happened, our bodies today would have to use different mechanisms to regulate pregnancy, libido, the response to stress, kidney function, inflammation, and the development of male and female characteristics at puberty,” Thornton said.

The findings were published online June 24 in the Proceedings of the National Academy of Sciences. The study was also covered by Wired UK.

Last year, Science Life spoke to Thornton about how he used a similar molecular time travel method to trace the evolution of proteins in ancient fungi, and help debunk the so-called “intelligent design” argument against evolution of complex structures.

Harms M.J., Eick G.N., Goswami D., Colucci J.K., Griffin P.R., Ortlund E.A. & Thornton J.W. Biophysical mechanisms for large-effect mutations in the evolution of steroid hormone receptors, Proceedings of the National Academy of Sciences, DOI:

About Matt Wood (531 Articles)
Matt Wood is a senior science writer and manager of communications at the University of Chicago Medicine & Biological Sciences Division.
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