This daily feast-and-famine cycle in oxygen availability created an intense physiological challenge for early animals, forcing them to develop adaptations to handle fluctuations in nutrients. For ...

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 ...

Earth’s history is filled with incredible milestones, and the emergence of the first animals is one of the most captivating.

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 ...

This animation created for Evolution: "Great Transformations" depicts creatures whose fossils were found at the Burgess Shale. As alien as these creatures seem, they are also surprisingly familiar.