中国内蒙古出土最古老的七鳃鳗幼鱼化石

Few people devote time to pondering the ancient origins of the eel-like lamprey, yet the evolutionary saga of the bloodsucker holds essential clues to the biological roots of humanity. Today, the Proceedings of the National Academy of Sciences published a description of fossilized lamprey larvae that date back to the Lower Cretaceous -- at least 125 million years ago.

They're the oldest identified fossils displaying the creature in stages of pre-metamorphosis and metamorphosis.

"Among animals with backbones, everything, including us, evolved from jawless fishes," said Desui Miao, University of Kansas Biodiversity Institute collection manager, who co-authored today's PNAS paper. "To understand the whole arc of vertebrate evolution, we need to know these animals. The biology of the lamprey holds a molecular clock to date when many evolutionary events occurred."

Miao said features of the human body come from the jawless fishes, such as the lamprey, a slowly evolving organism -- often parasitic -- which has inhabited Earth at least since the Devonian, about 400 million years ago.

"For example, a jawless fish such as a lamprey has seven pairs of gill arches, and the anterior pair of these gill arches evolved into our upper and lower jaws," he said. "Our middle ear bones? They come from the same pair of gill arches."

Indeed, lamprey evolution sheds light on the development of all animals with a backbone. Because of this, scientists have yearned to discover more history about the stages of the aquatic creature's three-phased life cycle.