No species are unitary individuals.<p>No, really, there&#x27;s no such thing. Everything alive is part of one ecosystem, and the only thing that really evolves is the ecosystem itself.<p>Don&#x27;t agree? Completely disconnect any apparently unitary individual from the planetary ecosystem and see how long it survives.<p>This has practical implications, especially for extended space flight. It turns out to be extraordinarily difficult to build a functioning and stable micro-ecosystem. Thinking at the species level is almost no help at all, because what actually happens is that chemicals, energy, and information propagate through the system space, and modify each other.<p>We don&#x27;t have good models to describe what happens at that level, which makes it very hard to build or maintain systems that are stable.<p>The Origin of the Species was a huge improvement on biblical creationism, but it would be disappointing if it was the last word on biological systems.