Evolution’s Random Paths Lead to One Place
A massive statistical study suggests that the final evolutionary outcome — fitness — is predictable.
In his fourth-floor lab at Harvard University, Michael Desai has created hundreds of identical worlds in order to watch evolution at work. Each of his meticulously controlled environments is home to a separate strain of baker’s yeast. Every 12 hours, Desai’s robot assistants pluck out the fastest-growing yeast in each world — selecting the fittest to live on — and discard the rest. Desai then monitors the strains as they evolve over the course of 500 generations. His experiment, which other scientists say is unprecedented in scale, seeks to gain insight into a question that has long bedeviled biologists: If we could start the world over again, would life evolve the same way? Many biologists argue that it would not, that chance mutations early in the evolutionary journey of a species will profoundly influence its fate. “If you replay the tape of life, you might have one initial mutation that takes you in a totally different direction,” Desai said, paraphrasing an idea first put forth by the biologist Stephen Jay Gould in the 1980s. Desai’s yeast cells call this belief into question. According to results published in Science in June, all of Desai’s yeast varieties arrived at roughly the same evolutionary endpoint (as measured by their ability to grow under specific lab conditions) regardless of which precise genetic path each strain took. It’s as if 100 New York City taxis agreed to take separate highways in a race to the Pacific Ocean, and 50 hours later they all converged at the Santa Monica pier. The findings also suggest a disconnect between evolution at the genetic level and at the level of the whole organism. Genetic mutations occur mostly at random, yet the sum of these aimless changes somehow creates a predictable pattern. The distinction could prove valuable, as much genetics research has focused on the impact of mutations in individual genes. For example, researchers often ask how a single mutation might affect a microbe’s tolerance for toxins, or a human’s risk for a disease. But if Desai’s findings hold true in other organisms, they could suggest that it’s equally important to examine how large numbers of individual genetic changes work in concert over time. “There’s a kind of tension in evolutionary biology between thinking about individual genes and the potential for evolution to change the whole organism,” said Michael Travisano, a biologist at the University of Minnesota. “All of biology has been focused on the importance of individual genes for the last 30 years, but the big take-home message of this study is that’s not necessarily important.” (via Yeast Study Suggests Genetics Are Random but Evolution Is Not | Simons Foundation)
I wrote a story recently about a cool technique called optogenetics, developed by bioengineering professor Karl Deisseroth, MD, PhD. He won the Keio Prize in Medicine, and I thought it might be interesting to talk with some other neuroscientists at Stanford to get their take on the importance of the technology. You know something is truly groundbreaking when each and every person you interview uses the word “revolutionary” to describe it.
Optogenetics is a technique that allows scientists to use light to turn particular nerves on or off. In the process, they’re learning new things about how the brain works and about diseases and mental health conditions like Parkinson’s disease, addiction and depression.
In describing the award, the Keio Prize committee wrote:
By making optogenetics a reality and leading this new field, Dr. Deisseroth has made enormous contributions towards the fundamental understanding of brain functions in health and disease.
One of the things I found most interesting when writing the story came from a piece Deisseroth wrote several years ago in Scientific American in which he stressed the importance of basic research. Optogenetics would not have been a reality without discoveries made in the lowly algae that makes up pond scum.
“The more directed and targeted research becomes, the more likely we are to slow our progress, and the more certain it is that the distant and untraveled realms, where truly disruptive ideas can arise, will be utterly cut off from our common scientific journey,” Deisseroth wrote.
Deisseroth told me that we need to be funding basic, curiosity-driven research along with efforts to make those discoveries relevant. He said that kind of translation is part of the value of programs like Stanford Bio-X – an interdisciplinary institute founded in 1998 – which puts diverse faculty members side by side to enable that translation from basic science to medical discovery.
See on scopeblog.stanford.edu