An international team of scientists says they’ve discovered what is likely the earliest known ancestor of humans.

An international team of scientists says they’ve discovered what is likely the earliest known ancestor of humans. 
They’ve named it Saccorhytus and describe the creature as a tiny, bag-like sea dweller with a disproportionately large mouth, according to a news release by the University of Cambridge.
The researchers’ theory is largely based on age, with the fossils examined dating back some 540 million years, and the determination that it belongs to the biological category of deuterostome, a sort that includes vertebrates. 
Examining the specimens took considerable effort.
Simon Conway Morris, one of the researchers, noted, "To the naked eye, the fossils we studied look like tiny black grains, but under the microscope the level of detail is jaw-dropping."
Aided by microscopes, the team was able to identify a number of features, including conical passageways that likely served to expel excess water taken in while feeding. 
It’s suggested those were the predecessors of gills.
Said Degan Shu, one of the team members, “Saccorhytus now gives us remarkable insights into the very first stages of the evolution of a group that led to the fish, and ultimately, to us.”