Snow geese migrating in North Dakota. Image credit: Rick Bohn (CC BY 2.0)

Birds of a feather evolve to flock together

Natural selection can allow a population to develop the ability to make coordinated movements.

In nature, we see many examples of highly coordinated movements of groups of individuals; think of a flock of birds turning swiftly in unison or a crowd of people filing through the exit of a building. A common feature of these behaviors is that they occur without any centralized control, and that they involve sudden and often dramatic changes in the ‘collective state’ of the group (i.e. speed, or the distances between individuals). In the past, researchers have likened these transitions in collective behavior to phase transitions in physical systems, for example, the transition between liquid water and water vapor. However, it is not clear how such collective responses could have evolved.

Natural selection is an evolutionary process whereby individuals with particularly ‘fit’ traits produce more offspring than others. Over many generations, these beneficial traits tend to become more common in the population. Andrew Hein, Sara Brin Rosenthal, George Hagstrom and co-workers developed a mathematical model to investigate whether the capacity of a population to perform collective motions could evolve through natural selection.

The model shows that over many generations, populations consistently evolve a unique collective trait whereby small responses of individuals to an environmental cue can cause spontaneous changes in the collective state of the local population. These transitions in collective state greatly enhance the ability of individuals to locate and exploit resources. The findings of Hein and co-workers suggest that natural selection acting on the behavior of individuals can cause a population to evolve a distinctive, collective behavior.

The next challenge will be to identify a biological system in which the evolution of collective motion can be studied experimentally to test these predictions.

To find out more

Read the eLife research paper on which this eLife digest is based: “The evolution of distributed sensing and collective computation in animal populations” (December 10, 2015).
Read a commentary on this research paper: “Collective Behaviour: Computing in fish schools”
eLife is an open-access journal that publishes outstanding research in the life sciences and biomedicine.
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