Physicists’ study of evolution in bacteria shows that
adaptations can be undone, but rarely. Ever since Charles Darwin
proposed his theory of evolution in 1859, scientists have
wondered whether evolutionary adaptations can be reversed.
Answering that question has proved difficult, partly due to
conflicting evidence. In 2003, scientists showed that some
species of insects have gained, lost and regained wings over
millions of years. But a few years later, a different team found
that a protein that helps control cells’ stress responses could
not evolve back to its original form. Here are the primary
results: They found that a very small percentage of evolutionary
adaptations in a drug-resistance gene can be reversed, but only
if the adaptations involve fewer than four discrete genetic
mutations. The findings will appear in the May 13 issue of the
journal Physical Review Letters. Lead authors of the paper are
two MIT juniors, Longzhi Tan and Stephen Serene. The paper is
not online yet. I’ll definitely check it ou