Darwin developed key aspects of his theory of evolution while pondering finches from the Galapagos Islands. It’s only fitting that reproductive biologist Michael Skinner would choose those same islands to propose a Lamarckian idea—that environment can directly impact inheritance of physical traits.
In this case, the process is driven by epigenetics, he says. “If we think about evolution, we can’t simply think of genetics. We also need to think about epigenetics.”
According to Skinner, epigenetic mutations occur 1,000 times more frequently than do genetic mutations and could help explain why new species emerge more often than expected.
“The reason epimutations exist might be to dramatically expand the number of variant individuals in a population,” he says. “Natural selection would then allow the best adapted among them to thrive and carry on—genome, epigenome, and all.”
His premise is supported by two recent studies in the Galapagos Islands involving Darwin’s finches, a group of birds noted for their diversity in beak size and function.
In the first study, Skinner’s team compiled a family tree for each of the sixteen finch species. They then plotted variations in species genome and epigenome.
“It turns out the farther a species diverged within the family tree, the more epigenetic changes we saw,” he says. “Genetic change also occurred but at a more random rate.”
Their second study compared finches of identical species who lived in different habitats. Previous investigators had found differences in beak structure, color, and weight depending on whether the birds lived in a wild environment or in town.
Together with University of Utah doctoral student Sabrina McNew, Skinner examined over 1,000 finches from rural and urban sites and discovered dramatic differences between the bird’s epigenetic patterns but virtually no variation in their DNA sequences.
“The biggest environmental difference between the two populations is diet,” he says. “In town, the birds land on outdoor tables and eat from your plate. So, it looks like nutrition caused the trait changes through epigenetics.”
Read more about Skinner and his work in our feature “Evolution evolution.”