Evidence from human famines and animal studies suggests that starvation can affect the health of descendants of famished individuals. But how such an acquired trait might be transmitted from one generation to the next has not been clear. A new study, involving roundworms, shows that starvation induces specific changes in so-called small RNAs and that these changes are inherited through at least three consecutive generations, apparently without any DNA involvement. The study, conducted by Columbia University Medical Center (CUMC) researchers, offers intriguing new evidence that the biology of inheritance is more complicated than previously thought. The study was published in the July 10, 2014 edition of the journal Cell.
The idea that acquired traits can be inherited dates back to Jean Baptiste Larmarck (1744–1829), who proposed that species evolve when individuals adapt to their environment and transmit the acquired traits to their offspring. According to Lamarckian inheritance, for example, giraffes developed elongated long necks as they stretched to feed on the leaves of high trees, an acquired advantage that was inherited by subsequent generations. In contrast, Charles Darwin (1809–82) later theorized that random mutations that offer an organism a competitive advantage drive a species' evolution. In the case of the giraffe, individuals that happened to have slightly longer necks had a better chance of securing food and thus were able to have more offspring. The subsequent discovery of hereditary genetics supported Darwin's theory, and Lamarck's ideas faded into obscurity.
"However, events like the Dutch famine of World War II have compelled scientists to take a fresh look at acquired inheritance," said study leader Oliver Hobert, PhD, professor of biochemistry and molecular biophysics and a Howard Hughes Medical Institute Investigator at CUMC. Starving women who gave birth during the famine had children who were unusually susceptible to obesity and other metabolic disorders, as were their grandchildren. Controlled animal experiments have found similar results, including a study in rats demonstrating that chronic high-fat diets in fathers result in obesity in their female offspring.
In a 2011 study, Oded Rechavi, a postdoctoral fellow in Dr. Hobert's laboratory, found that roundworms (C. elegans) that developed resistance to a virus were able to pass along that immunity to their progeny for many consecutive generations. The immunity was transferred in the form of small viral-silencing RNAs working independently of the organism's genome. Other studies have reported similar findings, but none of these addressed whether a biological response induced by natural circumstances, such as famine, could be passed on to subsequent generations.