Predators and prey typically show an evolutionary pattern called escalation. Life becomes more dangerous over evolutionary time: predators evolve more powerful weapons and prey evolve more powerful defences against them. There is both biogeographical and paleontological evidence for escalation.

The shells of these molluscs are an example of escalatory coevolution: the fossil record shows that the thickness of the shells increases in response to the evolution of more sophisticated predators.

Escalations are thought to be the biological factor most likely to cause extinction. As ecological competitors, or parasites and hosts, evolve against each other, if one competitor fails to evolve an adaptive improvement to keep up with its antagonists, it may go extinct.

Escalatory coevolution may effect both morphological and behavioral characters.

What is the difference between escalation and evolutionary progress?