by Zoe Pollock
Ed Yong reports on the fascinating case of a bird that raises another bird's offspring because evolutionarily it's easier than not:
Some battles aren’t worth fighting. The rewards of victory are too small or the costs of combat are too high. Good generals know this, and so does evolution. The natural world is full of intense arms races between predators and prey, hosts and parasites. If one side evolves a small advantage, the other counters it with an adaptation of their own, and both species are locked in an ever-escalating stalemate. But sometimes, these arms races never take off. The costs of engagement just aren’t worth it.