PULLMAN Two ground-breaking studies by Washington State University research teams are among the top 100 science stories of the year, according to Discover magazine. One of the teams, led by molecular biologist Michael Skinner, made the list for the second time in three years. Also making the list of top stories is research led by molecular anthropologist Brian Kemp.
Skinner and research associate Matthew D. Anway collaborated with
researchers at the University of Texas at Austin on a study showing that one-time exposure to an environmental toxin can affect the breeding behavior of the exposed animal’s descendants. In their experiments, male rats whose great-grandmothers had been exposed to an environmental toxin when they were embryos were much less attractive to female rats than males whose ancestors were toxin-free.
The study built on the WSU team’s previous “top science story,” their 2005 discovery that in utero exposure to a commonly-used fungicide produces cancers and other health problems in the exposed rat’s male descendants, through several generations. Skinner, Anway, and other colleagues at WSU showed that the transgenerational health consequences of toxin exposure were due to “epigenetic” changes involving small chemicals called methyl groups that are attached to an animal’s DNA.
In the 2007 study, the affected males were young and did not yet show signs of disease. While they appeared to be healthy, female rats could sense there was something different about themand they didn’t like it. Given the option of spending time with males with the ancestral exposure to toxin and males whose ancestors lacked such exposure, the females overwhelmingly chose to spend time with the unaffected males.
Skinner said the findings are significant because sexual selection, or how animals choose their mates, is a major determinant of evolutionary change.
“This is one of the first experimental studies to support a role for
epigenetics in evolutionary biology,” he said. “We showed that epigenetic changes can modify sexual selection in such a way as to influence the evolution of a species.”
Their study was published in the Proceedings of the National Academies of Science in March.
Discover’s top 100 list also featured Kemp’s research, which produced the oldest sample of human genetic material from the American continents ever examined. Working with David Glenn Smith and other colleagues at the University of California, Davis, Kemp extracted DNA from a 10,300 year-old human tooth.
Their findings, published last January in the American Journal of Physical Anthropology, support the hypothesis that humans arrived in North America later than previously thought and then migrated south along the Pacific coast.
The tooth was found in 1996 in On Your Knees Cave on Prince of Wales Island, Alaska.
The researchers compared the ancient tooth’s DNA with modern DNA to calculate when the first Americans landed on the coast of Alaska. Using a “molecular clock” of mutation rates, Kemp estimated the first arrivals happened within the last 15,000 years. Previous estimates had set the date as far back as 40,000 years.
To complete his study, Kemp examined a genetic database of 3,500 Native Americans and found that 1.5 percent of them shared the same genetic pattern in their mitochondrial DNA with that found in the toothand that almost all of the modern-day people sharing that pattern live on or near the coast, rather than inland.
The study of ancient DNA can open doors to discoveries not possible by studying only modern Native American DNA, Kemp said. “With the evidence from On Your Knees Cave and a handful of other recent studies, it is evident now that studying genetic variation solely in extant Native American populations will not be as informative about deep prehistory as has been previously assumed.”
The 2007 list of top science stories was announced in Discover magazine’s January issue, available now in print and online
(https://discovermagazine.com/) to subscribers.
