The scientific understanding of animal sentience has expanded dramatically, providing a stronger foundation for animal welfare policy and ethical consideration across a wider range of species.
The science of animal sentience is expanding the circle of moral concern with each decade. From the foundational recognition of mammalian consciousness to the growing evidence for fish pain, crustacean nociception, and invertebrate aversive experience, science is consistently demonstrating that the capacity for suffering extends much further than previously assumed. This has profound welfare policy implications — billions of fish, shrimp, and insects are farmed and killed under conditions that would be unacceptable if applied to vertebrates. The appropriate response to scientific uncertainty is the precautionary principle: where evidence of sentience exists, welfare protection should follow.