It probably feels obvious that having a close friend can influence your well-being. But do the groups that you’re a part of also affect your well-being? For example, does the culture of your work colleagues influence your productivity?
It may seem like the answer is also an obvious “yes.” But the idea that a group’s composition or structure can affect the individuals in it has been among the most controversial ideas in biology.
This phenomenon, called multilevel selection, is an extension of natural selection: the process by which organisms with traits better suited to their environment are more likely to survive and reproduce. Over generations, these advantageous traits – behavioral, morphological or physiological – become more common in the population.
In the traditional view of how evolution works, natural selection acts on an individual organism’s traits. For instance, mammals with more friends typically live longer lives and have more offspring. The trait under selection in this case is the number of social connections.
Multilevel selection proposes that at the same time selection is happening on the traits of individuals, selection also acts on the traits of groups. Here’s an example: Living in a more social and interconnected group may be beneficial for the members of that group, meaning the group’s traits are under selection. In nature, this means individuals in well-connected groups may live longer lives and have more offspring because well-connected groups may be better at finding limited resources or detecting predators. The traits of the group as a whole are what’s under selection in this case.
Multilevel selection could even select for traits that seem at odds at the individual and group levels. For instance, it could mean that selection favors individuals that are more reserved while at the same time favoring groups that are very social, or vice versa.
Multilevel selection has been a controversial idea since Charles Darwin first suggested that groups likely affect individuals in his 1871 book “The Descent of Man.”
The only evidence for multilevel selection acting simultaneously on individuals’ social relationships and on social groups comes from laboratory experiments. Experiments like these are vital to the scientific process, but without evidence for multilevel selection in wild animals, the 154-year-old debate rages on. As two field biologists interested in the evolution of behavior, we investigated multilevel selection in the wild by studying yellow-bellied marmots.
Our newly published study provides support for this contested concept, suggesting that the structure of the groups marmots are members of may matter for survival just as much as, if not more than, the friendly one-on-one relationships they have with other marmots.
Conner Philson observing the marmots’ social behavior.
G. Johnson
Spying on marmots’ social lives
It’s taken a…
