In some cases, a type II error may turn out to be a fatal mistake. A thirsty deer may not be able to run quickly enough to escape a predator, and an overcautious stag may not get to pass his genes on to the next generation. But on average, making this trade-off in favor of reducing the number of errors of self-harm while tolerating a higher number of errors of rejecting potential benefit has worked quite well for the species.
