by Barry King

For lovers of science and of nature, parasitism is a fascinating topic. An important detail is the complexity of the definition of "success" for the parasite, who prefers to rely on the productivity of others rather than on his own productivity (the cuckoo prefers not to be bothered by the hard work of building a nest, incubating eggs, and feeding chicks, so she just lays her eggs in someone else's nest.) The "success" of parasitism has an obvious strategic limitation in this consequence, that if the parasite is too "successful" the host is overwhelmed and goes extinct. Then the parasite goes extinct because it had become fatally dependent on a now-extinct host. Cuckoos can get away with it sustainably because they are parasitic only gently and on a wide variety of other species rather than on just one. A forest with cuckoos is more (bio)diverse than one without, but if the cuckoos collectively are not careful they will end up subtracting both their hosts and themselves from the biodiversity gene pool. That's why infectious organisms that cause 100% fatality in their hosts are extremely rare: their evolutionary tactic is strategically suicidal within just 1 or 2 generations. In human politics and economics, the analog to parasitism is misleadingly called "rent-seeking" (https://en.wikipedia.org/wiki/Rent-seeking) I guess it's a good thing that we humans are not aggressively parasitic organisms - or are we?