The find is the latest addition to an ever-growing body of evidence that challenges the commonly held belief that human evolution was a linear process from early primates to the humans we all know today. It also indicates that at least three different species of human lived simultaneously in Africa.
The anthropologists have discovered three human fossils; one of a face and two jawbones complete with teeth. The team estimate the fossils to be between 1.78 and 1.95 million years old.
The fossils support a theory that a skull found in 1972 is from Homo rudolfensis, a separate species of human. The skull had a long, flat face and a larger brain, which made it stand out from all other skulls that had been found at the time.
However, owing to the fact scientists only had the one skull, it was impossible to say with any degree of certainty whether anthropologists had really found a new species of human that lived alongside our other ancestors two million years ago, or just a random oddity.
The latest discoveries have given fossil researchers enough evidence to consider Homo rudolfensis a genuine species.
Up until 50 years ago, the only human ancestor that we knew of was a primitive species with small heads and prominent brows that existed around 1.8 million years ago and is known as Homo erectus.
Researchers then discovered another species that was even older than Homo erectus called Homo habilis that probably coexisted with Homo erectus. The latest discovery places a third species, Homo rudolfensis, in the same time period, and opens the door to the good possibility that there were more species of human around at the time.
It also opens the door on the debate of our previously supposed linear progression, characterised by the famous March of Progress picture. The finds instead indicate a wide range of diversity in our evolution.
Less straight forward?
Dr Meave Leakey, who led the research, told the BBC, “Our past was a diverse past, our species was evolving in the same way that other species of animals evolved. There was nothing unique about us until we began to make sophisticated stone tools.”
The finds show that a number of human prototypes were tried out before modern humans thrived, in the same way many other animals have evolved. Countless traits and mutations have been tried out by evolution over the years. Those that worked led to sight, flight, intelligence, or some other edge a species could use to prosper. Those that failed led to extinction.
Professor Chris Stringer of the Natural History Museum said that the latest finds human evolution worked in the same way as the rest of evolution.
“Humans seem to have been evolving in different ways in different regions. It was almost as if nature was developing different human prototypes with different attributes, only one of which, an ancestor of our species, was ultimately successful in evolutionary terms.”