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There is part of a structure in which every species is related to every other species. And they're built up on species, like a pyramid. The simpler cell organisms, and then the more complicated ones, all the way up to the mammals and birds and so forth. We call it 'developing upward'... The whole thing depends on every part of it. And we're taking out the stones from the pyramid.

There is part of a structure in which every species is related to every other species. And they're built up on species, like a pyramid. The simpler cell organisms, and then the more complicated ones, all the way up to