Scientists from the UK, China and Germany have recently discovered a balloon-like sea creature called Saccorhytus, the earliest known ancestor of humans. The findings were published in the journal Nature in January 2017.
The fossilised traces of this 540 million year old creature are exquisitely well preserved. This microscopic sea animal is the earliest known step on the evolutionary path that led to fish and humans.
• Saccorhytus is the most primitive example of a category of animals called deuterostomes which are common ancestors of a broad range of species including vertebrates.
• Saccorhytus was about a millimetre in size and is thought to have lived between grains of sand on the sea bed.
• Its body was symmetrical, which is a characteristic inherited by many of its evolutionary descendants, including humans.
• It was also covered with a thin, relatively flexible skin and muscles.
• It probably used to move by contracting its muscles and got around by wriggling.
• The most striking feature is its large mouth, relative to the rest of its body. It probably ate by engulfing food particles or even other creatures.
• However, the researchers could not find any evidence of anus in the creature, which suggests that it consumed food and excreted from the same orifice.
• The conical structures on its body might have allowed the water that it swallowed to escape and so these structures might have been the very early version of gills.
To the naked eye, the fossils look like tiny black grains, but under the microscope, the level of detail was jaw-dropping. Saccorhytus will render remarkable insights into the very first stages of the evolution of a group that led to the fish and then to human beings.
Until now, the deuterostome groups discovered were from between 510 to 520 million years ago.