Scientists find ‘oldest human ancestor’

Researchers in China have discovered the earliest known ancestor of humans and fish – the Saccorhytus. This 540 million year old fossil is “exquisitely” preserved and has given us a look into an area of our deep evolutionary past which had been hidden to us. 

This prehistoric animal was a millimetre in length and is thought to have lived between grains of sand on the sea bed. It was comprised mostly from a membrane of relatively flexible skin and muscle which allowed is to move through contraction and general wriggling motions – but its skin is far from the most remarkable characteristic identified from its fossilised remains.

The animal’s mouth is immediately striking as it takes up such a huge portion of its body. It is likely that the mouth evolved to be so large in order for the Saccorhytus to completely envelop food particles. In addition, there are conical structures present which indicate an early form of gills and point to how fish eventually descended from it. As the animal swallowed a food particle it would have inevitably swallowed water as well, and that water needed to escape from somewhere.

Perhaps the most interesting is the fact that it has a symmetrical “face”. This might not sound like something of note, but it is in fact an evolutionary trait which has been passed down over the last half a billion years to modern humans and fish, as well as other descendants such as star fish and sea urchins. 

The Saccorhytus represents a key stage in the evolutionary process. This tiny animal began to diversify into a whole range of more recognisable ancient animals as little as 10 million years later, meaning that this fossil represents a truly revolutionary animal with a family tree which defies expectation. 

Image copyright: JIAN Han, Northwest University, China