In his most famous work, Charles Darwin proposed that this amazing process is governed by a simple rule: selection of sufficiently fit individuals, spreading new traits by passing them on to offspring. But some of the scientific findings of recent years tend to complicate that simple picture. Among others is the understanding that every animal (and plant) is not a simple individual, but rather a composite ‒ a host living in symbiotic relationships with a variety of short-lived microorganisms. This begs the question: How do we reconcile the slow evolution of hosts with the much faster evolution of their microorganisms?
Prof. Yoav Soen of the Weizmann Institute of Science and his colleagues from Bar-Ilan University, Prof. Yitzhak Rabin, Prof. David Kessler and Dr. Dino Osmanovic, created a model of this intertwined evolution.
[B]acteria, including those in one’s microbiome, with their short lifespans and ability to pass on genetic changes, evolve much faster than their host. That is, bacteria can rapidly adapt to the changes in the host’s internal environment… Since gut bacteria have been shown to affect human traits as diverse as metabolism and mood, their ability to evolve within a person’s lifetime would influence their fitness in ways that had not previously been realized.
With the help of a microbiome, every host can acquire adaptive traits within its own lifetime and pass the newly acquired adaptation on to its offspring.