Asked by: Corben Jubian, Sydney, Australia
Eyes, by at least 40 million years. The only invertebrates with ears are land arthropods and they didn’t emerge until about 480 million years ago. Older invertebrates had antennae that would have been able to sense vibrations in the water, but that’s not quite the same thing as hearing. Trilobites already had complex compound eyes 521 million years ago, and simple eyespots without a lens probably date back to 570 million years ago, when the first multicellular animals appeared.