dramatically. It was the time of the Cambrian Explosion, an eruption of life when Earth’s very first animals began appearing in the fossil record — the ancestors of all major animal groups ...

The Cambrian Explosion saw an incredible diversity of life emerge, including many major animal groups alive today. Among them were the chordates, to which vertebrates (animals with backbones ...

All animal evolution for the last half billion years has come from tinkering with these Cambrian body plans. Then, between about 570 and 530 million years ago, another burst of diversification ...