Coevolution

Origins and definition

Charles Darwin (1859, 1862) held that flowers and insects had changed in response to each other. Seeing the nearly 30-centimeter nectar spur of the Madagascar orchid Angraecum sesquipedale, he predicted a moth with an equally long tongue, which was found after his death. The term "coevolution" was popularized by Ehrlich and Raven (1964), who analyzed butterfly larvae and the chemical defenses of their host plants: plants evolve toxins, some insects evolve detoxification, and those insects then diversify on the newly available hosts, an "escape and radiate" model. Daniel Janzen (1980) proposed a strict definition: coevolution occurs only when a trait in one species changes in response to another species and that species in turn responds to the change. Coevolution thus deals with natural selection in an environment that is itself continually evolving.

Antagonistic coevolution and mutualism

In antagonistic relationships, "evolutionary arms races" arise in which each improvement on one side must be matched by the other (Dawkins and Krebs, 1979). Leigh Van Valen (1973), borrowing the Red Queen's remark in Through the Looking-Glass that one must keep running to stay in place, proposed the "Red Queen hypothesis": species keep adapting, but because their antagonists also evolve, their relative fitness stays the same. The idea is also used to explain sexual reproduction as a defense against parasites. Brodie et al. (2002) studied tetrodotoxin-bearing newts and the garter snakes that evolved resistance to their poison, and Paterson et al. (2010) showed in experimental evolution of bacteria and viruses that antagonistic coevolution accelerates molecular evolution. In mutualism, mutually beneficial traits evolve together; Lynn Margulis (1970) proposed endosymbiotic theory, in which mitochondria and chloroplasts were once free-living bacteria, linking to the evolution of cooperation.

The geographic mosaic and extensions to culture

John Thompson (2005) proposed the "geographic mosaic theory," in which coevolution proceeds differently across places: some are "hotspots" of strong reciprocal selection, others "coldspots," and gene flow mixes them into species-wide coevolution. Theoretically, Kauffman and Johnsen (1991) used coupled fitness landscapes to argue that coevolving systems self-organize to the edge of order and chaos, connecting to self-organization and chaos theory. In humans, gene–culture coevolution matters: Durham (1991) and Laland et al. (2010) described how culture changes genetic selection, as when adult lactase persistence spread in populations with dairying. "Coevolution" is also used as a metaphor for mutual change between technologies and institutions or firms and ecosystems, but that use should be distinguished from the biological sense.

FAQ

How does coevolution differ from species simply adapting together?

Two species each adapting to the same environment is not coevolution. It is coevolution when a change in one species exerts selection on another and that response in turn affects the evolution of the first.

What does the Red Queen hypothesis explain?

It explains why species keep adapting without greatly improving their prospects, because their antagonists also evolve, and why traits that speed adaptation, such as sexual reproduction, are maintained.

Sources reviewed: 2026-10-26

References

1. Darwin, C. (1859). On the Origin of Species. London: John Murray.
2. Darwin, C. (1862). On the Various Contrivances by which British and Foreign Orchids are Fertilised by Insects. London: John Murray.
3. Ehrlich, P. R., & Raven, P. H. (1964). Butterflies and plants: A study in coevolution. Evolution, 18(4), 586–608.
4. Janzen, D. H. (1980). When is it coevolution? Evolution, 34(3), 611–612.
5. Van Valen, L. (1973). A new evolutionary law. Evolutionary Theory, 1, 1–30.
6. Dawkins, R., & Krebs, J. R. (1979). Arms races between and within species. Proceedings of the Royal Society B, 205(1161), 489–511.
7. Thompson, J. N. (2005). The Geographic Mosaic of Coevolution. Chicago: University of Chicago Press.
8. Brodie, E. D., Jr., Ridenhour, B. J., & Brodie, E. D., III (2002). The evolutionary response of predators to dangerous prey: Hotspots and coldspots in the geographic mosaic of coevolution between garter snakes and newts. Evolution, 56(10), 2067–2082.
9. Paterson, S., Vogwill, T., Buckling, A., et al. (2010). Antagonistic coevolution accelerates molecular evolution. Nature, 464(7286), 275–278.
10. Margulis, L. (1970). Origin of Eukaryotic Cells. New Haven, CT: Yale University Press.
11. Durham, W. H. (1991). Coevolution: Genes, Culture, and Human Diversity. Stanford, CA: Stanford University Press.
12. Laland, K. N., Odling-Smee, J., & Myles, S. (2010). How culture shaped the human genome: Bringing genetics and the human sciences together. Nature Reviews Genetics, 11(2), 137–148.
13. Kauffman, S. A., & Johnsen, S. (1991). Coevolution to the edge of chaos: Coupled fitness landscapes, poised states, and coevolutionary avalanches. Journal of Theoretical Biology, 149(4), 467–505.