LIFE × EVOLUTION

The First Eyes

~515 million years ago

Phanerozoic · Paleozoic · Cambrian

One shale in South Australia has yielded two kinds of fossil eye. One pair, two to three centimetres across and set with at least sixteen thousand hexagonal lenses in each eye, belonged to the top predator of those seas and rivalled the sharpest compound eyes alive today. The other, from a smaller arthropod, carries more than three thousand lenses and a patch where they widen: a bright zone, the arrangement an animal uses to hunt in dim water.

Why it matters

Light-sensitive spots are far older, probably Precambrian. What appears here is the lens, and a lens turns the detection of light into an image. Once one animal could make out another at a distance, hiding, armour and speed all started to pay for themselves, which is why vision is a plausible engine of the Cambrian explosion.

Dating & uncertainty

The 515 Ma date belongs to the oldest eyes preserved in this detail. Light-sensitive organs are certainly older, and probably Precambrian, so what this shale dates is the lens rather than the light sense itself.

Sources

1. Paterson et al. (2011), Nature · Acute vision in the giant Cambrian predator Anomalocaris and the origin of compound eyes
2. Lee et al. (2011), Nature · Modern optics in exceptionally preserved eyes of Early Cambrian arthropods from Australia
3. Schoenemann (2025), Arthropoda · Trilobite eyes and their evolution

Earth history as one day

21:16:392 h 43 min before midnight

if Earth’s 4.54 billion years were compressed into a single day