Have We Found Mankind's Oldest Ancestor?

For archaeologists, delving into the history of mankind is endlessly fascinating. Now, a team of researchers from the University of Cambridge have made a milestone discovery that offers brand new insight into how the human race evolved.

Estimated to be around 540 million years old, the fossil is ancient to say the least. It was found in China’s Shaanxi province, buried deep in sedimentary rock. The team have named it Saccorhytus coronaries, and describe it as a tiny speck of sand made up of a bag-like body and wrinkled mouth. They also point out that the organism has no anus, as well as thin, flexible skin suggesting that it was made up of muscles.

The bilateral symmetry link

So what prompted the team to compare the wildly unsophisticated organism with modern day humans? Apparently, the creature is bilaterally symmetrical, which is a key feature of homo sapiens. They’ve since acclaimed the fossil as mankind’s oldest known ancestor, and published their findings 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,” comments Simon Conway Morris, co-author of the report. “All deuterostomes had a common ancestor, and we think that is what we are looking at here."

The all-important deuterostome link

Encompassing a broad group of vertebrates, echinoderms and hemichordates, deuterostomes are defined by their deuterostomic embryonic development. This sees the first embryotic opening (the blastopore) become the anus, as opposed to protostomes where it becomes the mouth. It was this unique characteristic that led the team to make the connection, and identify the fossil as a prehistoric human ancestor.

Other observations include a quartet of openings on either side of its body, which could be the beginnings of gill slits. Its body is also speckled with tiny pores, which scientists suggest could play a physical or sensory role.

Unravelling the mysteries of the Cambrian period

While this isn’t the first deuterostome that scientists have studied, it is round 20 to 30 million years older than its counterparts. This meant it would have lived in the early Cambrian period, which was an era of mass diversification for the species.

“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,” comments co-author Degan Shu.

Not only does the fossil offer a fascinating glimpse at early evolution, but it could also help to shed light on the fossil record gap mystery.

“If indeed the first of these animals including Saccorhytus were very, very tiny, they could only preserve in very, very exceptional circumstances – they basically slip through the fossilisation net,” explains Morris.

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