“We like our black-and-white narratives, with clear heroes and villains. In the last few years, I’ve seen the viewpoint that “all bacteria must be killed” slowly give ground to “bacteria are our friends and want to help us”, even though the latter is just as wrong as the former. We cannot simply assume that a particular microbe is “good” just because it lives inside us. Even scientists forget this. The very term symbiosis has been twisted so that its original neutral meaning – “living together” – has been infused with positive spin, and almost flaky connotations of cooperation and harmony. But evolution doesn’t work that way. It doesn’t necessarily favour cooperation, even if that’s in everyone’s interests. And it saddles even the most harmonious relationships with conflict.
“We need to separate important from harmonious. The microbiome is incredibly important but it doesn’t mean that it’s harmonious,” says evolutionary biologist Toby Kiers.15 A well-functioning partnership could easily be seen as a case of reciprocal exploitation. “Both partners may benefit but there’s this inherent tension. Symbiosis is conflict – conflict that can never be totally resolved.”
14. Oxpeckers: Weeks, 2000; cleaner fish: Bshary, 2002; ants and acacias: Heil et al., 2014.
Weeks, P. (2000) ‘Red-billed oxpeckers: vampires or tickbirds?’ Behav. Ecol. 11, 154–160.
Bshary, R. (2002) ‘Biting cleaner fish use altruism to deceive image-scoring client reef fish’, Proc. Biol. Sci. 269, 2087–2093.
Heil, M., Barajas-Barron, A., Orona-Tamayo, D., Wielsch, N., and Svatos, A. (2014) ‘Partner manipulation stabilises a horizontally transmitted mutualism’, Ecol. Lett. 17, 185–192.
15. West, S.A., Fisher, R.M., Gardner, A., and Kiers, E.T. (2015) ‘Major evolutionary transitions in individuality’, Proc. Natl. Acad. Sci. U. S. A. 112, 10112–10119.