But we know now that that picture is incomplete. Evolutionary progress can be propelled both by the competitive struggle to adapt to an environment, and by the relaxation of selective forces. When natural selection on an organism is relaxed, the creative powers of mutation can be unshackled and evolution accelerated. The relief of an easier life can inspire new biological forms just as powerfully as the threat of death.
One of the best ways to relax selective forces is to work together, something that mathematical biologist Martin Nowak has called the “snuggle for survival.” New research has only deepened and broadened the importance of cooperation and lifting of selective pressures. It’s a big, snuggly world out there. [...]
We tend to conceive of life as separate from its habitat: The environment is a kind of container, and life is like a liquid that adapts to fill it. Sir Arthur Tansley introduced the concept of the ecosystem in 1935. He believed nature operated like a machine, and so, like an engineer, sought to map the flow of energy and matter through life and its environment. But an ecological niche is not, as I’d gathered from building shoebox dioramas in second grade, the raw physical parameters of an animal’s environment: salinity, alkalinity, humidity, temperature. It’s a web of relations, not just between a species and its habitat, but also with all the other species co-existing in the same space. A niche is no less dynamic than evolution is, contrary to Tansley’s mechanistic vision. “Palaeontologists often say that a burst of diversity in the fossil record simply ‘filled in ecological space,’ as if each new species simply took up residence in a square of a pre-existing chessboard,” writes paleobiologist Douglas Erwin. He suggests that a better analogy is that species build the chessboard themselves. Corals, for example, form their own protective niche by building reefs, which slow currents and reduce erosion on themselves. Reefs also serve to house countless other species, many of which have in turn evolved behaviors to protect corals. If an organism can modify its niche—by altering itself or its relationships with other species—it has the chance to build the world in which its future progeny will evolve, reshaping it to better ensure their survival.
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