Take a look at your distant ancestor. That beauty is the best candidate yet for the earliest ancestor of humans.
As small as a speck of sand, it had a bag-like body with a large, wrinkled mouth and no anus. It was also bilaterally symmetrical, meaning it had mirrored halves – a key feature of many of its descendants, including humans.
Spot the resemblance now? Okay, so it’s a distant relative at 540 million years old. The fossil of this ancient creature was found in sedimentary rock in China’s Shaanxi province and subsequently dubbed Saccorhytus coronarius. The discovery is published in the journal Nature.
“To the naked eye, the fossils we studied look like tiny black grains, but under the microscope the level of detail is jaw-dropping,” said co-author Simon Conway Morris of the University of Cambridge in a statement. “All deuterostomes had a common ancestor, and we think that is what we are looking at here."
Deuterostomes are a broad group that includes vertebrates (such as humans), echinoderms (such as starfish), and hemichordates (acorn worms). Literally, deuterostome means "mouth second”, as the first opening to develop in the embryo is that of the anus.
However, if indeed the creature had no anus, then the waste from the food it gulped down would have been excreted through where it came – the mouth. And while it’s not unheard of for an animal to lack an anus, Morris admits it’s possible the team just haven’t found it yet.
This creature may be the earliest known prehistoric ancestor of humans. So, you know, take a snapshot and add it to your family album. Jian Han, Northwest University, China
In addition to its puckered orifice, the critter had thin, relatively flexible skin, suggesting it had musculature that allowed it to wriggle around.
There are four openings on either side of the body that researchers suggest could be the precursor to gill slits. Tiny pores speckled across its body are more mysterious. The authors propose that they secured the critter to grains of sand or they had a sensory role.