Scientists Just Discovered the Oldest Recorded Footprints in History on an Ancient Seabed
Last March, archaeologists found the oldest human footprints ever discovered, located on a beach on Calvert Island in Canada. Those footprints were dated to be between 11,000 and 14,000 years old, making them twice as old as the earliest human civilization.
Pretty old, right? Well, no, not compared to the footprints just discovered in the Dengying Formation in southern China—these marks are the first known evidence of feet.
The footprints were left by a very early bilaterian, a type of animal with bilateral symmetry (usually characterized by a head at the front, legs on either side, and a back portion at its rear).
For comparison, non-bilateral animals include sponges, corals, jellyfish, and anemones.
Previously, it was thought that bilaterian animals first appeared between 541 and 510 million years ago during the Cambrian Explosion, a period where primitive life on Earth suddenly started evolving into new and diverse forms, but these little footprints are estimated to be between 551 and 541 million years old, placing them in the Ediacaran period.
Life during the Ediacaran was characterized by algae, lichens, giant protozoans, worms, and various bacteria, but there's still a lot that paleontologists don't know about it.
The footprints themselves look like two rows of holes punched in the ancient sediment and apparently lead away from the remains of a burrow.
This suggests that whatever made the prints (scientists still aren't sure what animal they belong to) probably survived by digging into the seafloor to find food and consume oxygen.
Because the footprints are trace fossils, not fossils of the animal itself, it's going to be difficult to credit a particular branch of the Tree of Life with the title of "First to Develop Limbs."
Still, this discovery means that paleontologists will have to revise their vision of how life developed in Earth's primordial oceans.