Haikouichthys

The Origin of all Vertebrae

The exact origin of vertebrates is not known. It is thought that the separation between vertebrates and invertebrates occurred about 600 million years ago in the Precambrian. The oldest vertebrate found is Haikouichthys, a primitive fish that lived 535 million years ago in the Cambrian. Its body was small, without distinct fins, but it had eyes, gills, a nose, ears, and a brain.

It was one of the most advanced animals in the Cambrian and is still our oldest ancestor. This fish, the ancestor of all vertebrates, was discovered in 1999 in the southern Chinese locality of Haikou, and the name Haikouichthys simply means fish from Haikou.

Haikouichthys possessed only one jawless mouth and lived in large groups of conspecifics due to its small body size (2.5 cm). These groups, also called schools, moved along the bottom of the sea, sucking up food particles and offering their members protection from predators.

The first discovery of a fossil of Haikouichthys was followed by others in good condition in the years that followed. Some were in such good condition that even internal organs and mucous glands could be seen. The mucus glands were responsible for moistening the skin. The body could thus reduce its resistance to flow and Haikouichtys could move faster in the water.

All descendants of this primitive creature possessed mucus glands from then on. So did the much later appearing mammals - and we humans. In addition, the function of the mucus glands has changed considerably in the course of evolution. For example, today we possess sweat glands and mammary glands, which are not dissimilar to the ones of our ancestors. And all thanks to a tiny little fish.