Scientific evidence for sentience in invertebrates is advancing rapidly, challenging longstanding assumptions and prompting reconsideration of how billions of these animals are treated.
The question of invertebrate sentience has profound welfare implications because invertebrates are the most numerically abundant animals used by humans: billions of insects are killed as pests, trillions of crustaceans are boiled alive annually, and insects are increasingly farmed for food. If meaningful fractions of these animals have subjective experiences including pain and distress, the scale of potential suffering is enormous. Scientific conservatism is appropriate, but the regulatory precautionary principle now being applied — treating animals as sentient when the evidence is plausible but not certain — reflects appropriate moral seriousness about the stakes.