A new review published in Frontiers in Ecology and Evolution reports on Mar. 13 that natural selection operates across multiple levels of life, from genes to groups and entire communities, rather than acting solely on individual organisms. The study was co-authored by Michael Wade, Distinguished Professor Emeritus of Biology at Indiana University Bloomington.
The findings challenge a long-standing belief in evolutionary biology that natural selection mainly targets individuals. This broader understanding could influence fields such as cancer research and agriculture, potentially changing how scientists approach complex biological problems.
The research team, led by César Marín of Universidad Santo Tomás in Chile along with colleagues from the Netherlands and the United States, conducted a systematic review of nearly 3,000 scientific articles published between 1900 and 2024. After applying strict criteria—excluding theoretical models and opinion pieces—they identified 280 peer-reviewed studies documenting multilevel selection (MLS), where natural selection acts simultaneously at more than one level of biological organization. These studies covered a wide range of organisms including viruses, bacteria, fungi, social insects like ants and bees, wild birds, mammals, crop plants, and humans.
Wade said: “The paper is significant because it surveys field and experimental research around the world on multilevel selection, based on experimental work that I’ve done, as well as the ensuing research of my students, and those influenced by this research.” He pointed out practical applications: “On the applied side, for several decades now, cancer biologists have described the origin and spread of malignant tumors as a multilevel selection process acting among cells in the human body. Moreover, animal breeders have turned to multilevel selection to increase things like egg yield and diminish feather pecking, a revolution in the way domestic animals and plants are reared.”
One example cited is William Muir’s work at Purdue University showing that selecting egg-laying hens as groups rather than individuals dramatically reduced mortality from aggressive behavior while increasing egg production. Another experiment with yeast demonstrated how artificial selection for larger group size led to visible clusters resembling early multicellular life forms.
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The review found that most MLS studies were published recently—199 out of 280 since 2012—indicating growing acceptance across disciplines. The authors note some limitations due to possible publication bias but suggest skepticism about group-level effects is fading.
Looking ahead, Wade said new molecular tools will likely lead researchers toward more discoveries using MLS frameworks: “This scholarship points toward a future in which researchers study multilevel selection as a standard analytical lens… applicable wherever organisms live, compete, and reproduce in social groups.”
