Toby Kiers is an American evolutionary biologist who is a University Research Chair and professor at Vrije Universiteit Amsterdam.

[6] She did her Ph.D. at UC Davis, completing a thesis entitled Evolution of cooperation in the legume-rhizobium symbiosis in 2005 supervised by Robert Ford Denison.

Her observations are that fungi in the soil behave as economic agents in a free-market system, supplying more phosphorus to plants that are able to deliver more sugar in exchange.

[9][10][11] Based on this hypothesis, Kiers is interested in developing fungi that behave "altruistically" in their environment to foster efficient plant growth and reduce the need for fertilizers.

To track the flow of nutrients, Kiers has pioneered the use of quantum dots to tag molecules so that they fluoresce and can be more easily differentiated.

By assuming that each organism acts to further its own personal gain, the theory neglects the possibility that plants and fungi may exist in a fully collaborative relationship with well-aligned interests.