INVENTING THE EGG

This period saw one of the largest leaps in the evolution of vertebrate species with the ‘invention’ of the amniote egg around 340 million years ago. Amniotes, a group of animals that includes reptiles, birds and some mammals, produce an egg with a tough protective shell and a series of life-supporting membranes that surround the developing offspring within. Before the amniote egg, fish and amphibians could only lay their eggs in water. However, as reptiles began to evolve and created tougher eggs that could be laid anywhere on dry land, the amniote egg was born. This ability to give birth out of the water was one of the main factors that facilitated further diversity of life on Earth.

The first hard-shelled eggs were around 280 million years before chickens evolved