Indiana University biologist contributes to landmark review reshaping how evolution is understood
Bloomington, Indiana – For generations, biology textbooks have described evolution largely as a contest among individual organisms. Each one struggling to survive, reproduce, and pass along its genes. A sweeping new scientific review, however, is challenging that long-standing view.
Drawing from nearly half a century of research, scientists have found compelling evidence that natural selection operates simultaneously across several layers of life, from genes and cells to entire groups and communities.
The landmark review includes the work of Michael Wade, Distinguished Professor Emeritus of Biology in the College of Arts and Sciences at Indiana University Bloomington. Published in the journal Frontiers in Ecology and Evolution, the study compiles decades of research that point toward a more complex picture of how evolution unfolds in the natural world.
Rather than acting solely on individuals, the research shows that natural selection can shape multiple levels of biological organization at the same time. Known as “multilevel selection,” the concept suggests that evolutionary change can occur not only within organisms, but also within the groups, colonies, or communities they form.
To investigate this idea, an international team of researchers led by César Marín of Universidad Santo Tomás in Valdivia, Chile conducted a detailed review of scientific literature spanning more than a century.
Their bibliometric analysis examined nearly 3,000 scholarly articles published between 1900 and 2024. After applying strict criteria, excluding theoretical papers, opinion pieces, and studies lacking direct evidence, the team identified 280 peer-reviewed studies that clearly documented multilevel selection in action.
These studies reveal that multilevel selection occurs across an extraordinary range of living systems. Researchers documented the phenomenon in organisms as small as viruses and bacteria, and as complex as mammals, birds, insects, and even humans.
Most of the studies examined selection acting on groups such as colonies of social insects, clusters of microorganisms, or populations of wildlife. Others explored selection occurring at even broader levels, including interactions among entire communities of species.
The roots of this work trace back to experiments conducted by Wade in the 1970s. In laboratory studies involving flour beetles, Wade demonstrated that controlling which groups of beetles reproduced could dramatically reshape entire populations within only a few generations. Those early findings offered some of the first clear evidence that natural selection could act on groups, not just individuals.
Over the decades that followed, the idea sparked a growing body of research. Today, the implications extend far beyond evolutionary theory. In medicine, for example, cancer researchers often describe tumor development as a multilevel selection process occurring among cells within the human body. In agriculture, similar principles have helped animal breeders improve productivity while reducing harmful behaviors.
One notable example involves egg-laying hens. When breeders selected entire groups of birds rather than the most productive individuals, aggressive feather-pecking dropped dramatically while egg production surged. Similar insights have emerged from experiments with yeast, where repeated selection for larger groups eventually led single-celled organisms to form visible clusters—echoing one of life’s earliest evolutionary transitions toward multicellular organisms.
The review also reveals that interest in multilevel selection is accelerating. Of the 280 studies included, the majority were published between 2012 and 2024, reflecting growing recognition of the concept across many fields of biology.
While the authors acknowledge that some studies may remain unpublished or use different terminology, the accumulated evidence points toward a significant shift in evolutionary thinking.
With modern genetic tools and increasingly detailed ecological data, researchers now have more ways than ever to explore how life evolves, not just through the success of individuals, but through the dynamics of the groups and communities they inhabit.
