Researchers from Cambridge University have identified traces of what they believe is our earliest known prehistoric ancestor, and the microscopic, bag-like sea creature ain’t good looking.
A tiny sea creature that lived about 540 million years ago has been identified from microfossils found in China and boffins think it may be the earliest known step on an evolutionary path that eventually led to the emergence of human beings.
Our new long-lost relative has been named Saccorhytus, after the sack-like features created by its elliptical body and large mouth. It is thought to be the most primitive example of a so-called ‘deuterostome’ – a broad biological category that encompasses a number of sub-groups, including vertebrates. If researchers are right, then Saccorhytus was the common ancestor of a huge range of species, and the earliest discovery yet on the evolutionary path that eventually led to humans, hundreds of millions of years later.
Interestingly, scientists haven’t been able to find much in the way of a family resemblance to us modern humans. Even though the millimetre-sized Saccorhytus’ features were spectacularly preserved in the fossil, researchers have been unable to find any evidence that the animal had an anus.
No wonder she looked so bloated.
Professor of Evolutionary Palaeobiology at the University of Cambridge, Simon Conway Morris, thinks the finding may represent the primitive beginnings of a very diverse range of species,
“To the naked eye, the fossils we studied look like tiny black grains, but under the microscope the level of detail is jaw-dropping. All deuterostomes had a common ancestor, and we think that is what we are looking at here.”
The research team say that most other early deuterostome groups are from about 510 to 520 million years ago, when they had already begun to diversify into not just the vertebrates, but animals such as starfish and sea urchins and groups including things like worms.
This level of diversity has made it extremely difficult to work out what an earlier, common ancestor might have looked like. Until now.
“Our team has notched up some important discoveries in the past, including the earliest fish and a remarkable variety of other early deuterostomes. 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.”
The Saccorhytus microfossils were found in Shaanxi Province, in central China, and pre-date all other known deuterostomes. By isolating the fossils from the surrounding rock, and then studying them both under an electron microscope and using a CT scan, the team were able to build up a picture of how the creature might have looked and lived.
The study suggests that its body was bilaterally symmetrical (a characteristic inherited by many of its descendants, including humans) and was covered with a thin, relatively flexible skin. This in turn suggests that it had some sort of musculature, leading the researchers to conclude that it could have made contractile movements, and got around by wriggling.
Perhaps its most striking feature, however, was its rather primitive means of eating food and then dispensing with the resulting waste. Saccorhytus had a large mouth, relative to the rest of its body, and probably ate by engulfing food particles, or even other creatures. A crucial observation are small conical structures on its body. These may have allowed the water that it swallowed to escape and so were perhaps the evolutionary precursor of the gills we now see in fish.
But where did their poo go?
“Any waste material would simply have been taken out back through the mouth, which from our perspective sounds rather unappealing.”
Mingin’. Won’t be inviting him to the family reunion with table manners like that.
Main image: Broad City/ Comedy Central
