I find that a lot of things are really DAGs or full on graphs but are easier to reason about as roughly trees. Website structures, for example. All knowledge, even. For some reason, trees are so much easier to hold in the head.
Natural selection is a good model not just for technology, but for ideas in general. Ideas have their own lifespans and virality coefficients, but they're like viruses in that they depend on their hosts, so their fitness is partially dependent on the fitness of their hosts. That's why our morals exist, because societies that had them were more fit than societies where everyone was totally selfish. We don't like to think of morality in terms of fitness though, because of our morals, ironically.