Dissecting post-Palaeozoic arms races

In the last 40 years, there has been a dramatic increase in our knowledge about predator–prey interactions in the fossil record. Studies have become more focussed to testing specific hypotheses concerning arms races and have employed increasingly sophisticated analyses. Using evidence from crushing and, in particular, drilling predation (largely on molluscan prey), it has been possible to show an episodic increase in predation pressure over time, accompanied by enhancement of predatory methods and behaviour. A wide range of defensive adaptations (life habit, morphological, and behavioural) is thought to have evolved in response to this increase in predation pressure. The consensus is that over evolutionary timescales, escalation may be more important than coevolution in most instances, but the two are difficult to distinguish from the fossil record. Our data are very ‘noisy’ and future work should concentrate on trying to provide a wider spread of data (e.g., from different target organisms) and seek to focus on specific regions or environments that have been less well studied.