One of the most fascinating questions in human evolutionary studies is when and where the last common ancestor of apes and humans lived. Within the last few months, new evidence has emerged from southeastern Europe that has dramatic bearing on this question.
When and where did the last common ancestor live?
It has always been assumed that the last common ancestor to the ape and human lines lived somewhere in Africa. The simple reason for this is that Africa is where we find our closest relatives, the gorillas and chimpanzees. The field of genetics has provided the best evidence yet of our common ancestry with modern great apes The genetic similarity between humans and chimpanzees is 99.4%. Furthermore, humans and great apes have a large number of shared errors and mutations in their genetic codes.
Also bolstering this view is the almost continuous discoveries of early humans (taxonomically known as “hominins”) in north and east Africa, that have pushed the precursors of the genus Homo back to at least six million years ago, living in modern-day Kenya. While this evidence is incomplete, skeletal fragments indicate that by this time, our ancestors were likely walking on two legs.
But these finds represent populations of hominins that have evolved since the common ancestor. When did this event take place? The most recent research has settled on a date of at least seven or eight million years ago and possibly as early as thirteen million years ago.
Have we been looking in the wrong place?
Within the last year, evidence has surfaced that suggests we may be looking in the wrong place for this last common ancestor. In May of 2017, researchers re-examined a partial fossil ape jaw, given the name Graecopithecus, that had been unearthed during World War II in Athens, Greece, as well as a tooth from the same species found in Bulgaria. They discovered something startling: The shape and form of the tooth and roots in the jaw had hominin characteristics. Furthermore, based on the animal and plant remains found with the fossils, the jaw and tooth were estimated to be over seven million years old.
This led the researchers to suggest the possibility that the hominin line may have originated in southern Europe. As palaeoanthropologist David Begun said: “The findings call into question one of the most dogmatic assertions in paleoanthropology since Charles Darwin, which is that the human lineage originated in Africa.”
Source: https://doi.org/10.1016/j.pgeola.2017.07.006. Used by permission.
The New Find From Crete
At approximately the same time, working on the island of Crete, researchers uncovered a set of footprints that are, despite being small, indistinguishable from those made by humans. Humans move around very differently from apes. They plant the ball of their foot, pivot and then use the toes to push off to take a step. Apes, when they get up on two legs, sway from side to side and walk in a halting and slow fashion.
It was not just the presence of the hominin tracks that got the researchers excited. It was the date: the tracks are 5.7 million years old. This means that the creature who made them lived about the same time as Orrorin tugenensis, in Kenya, some eight thousand miles to the south.
How did they get to Africa?
But if the earliest members of our line did live in this area of southern Europe, how did they get to Africa? The age of these tracks places them squarely within what is called the Messinian Salinity Crisis, a time between seven and five million years ago in which the Mediterranean Sea almost completely dried up, leaving large areas of exposed land. During this time, Crete was an extension of the Greek peninsula and north Africa was lush and verdant. Although the Sahara Desert was beginning to form, it was millions of years away from reaching its current extent.
It is therefore possible that a migration route existed between the northern and southern shores of the dried-up Mediterranean Sea and that the early human fossils that we find in north Africa are the descendants of those that originated in extreme southern Europe.
If the ancestors of the human and ape lines really did originate in southeastern Mediterranean Europe, it leaves some unanswered questions. For one, if the last common ancestor is in Europe, why are all its descendants in Africa? So far, all the earliest fossil hominins have been found in north and east Africa. Additionally, why have we found no hominins like Australopithecus in southern Europe? So far, all that has come out of the ground in this region is apes between 8 and 15 million years old.
On the other hand, as noted above, this all happened against the backdrop of a Mediterranean region that looks very different than the (much more watery) present condition. If this is so, it raises the dark and ominous prospect that much of the information regarding the last common ancestor lies at the bottom of the Mediterranean Sea. It would also mean that the earliest hominins had a range that extended from the northern shores of the Mediterranean Sea to east Africa.
Does This Change Our Understanding of Human Evolution?
Does the possibility that our line had its beginnings in southern Europe change our understanding of human evolution? Absolutely it does. It dramatically expands the geographical range in which the human/great ape split may have taken place. Furthermore, it potentially shifts the focus away from the African continent and to an area that, until recently, no one had considered. Despite the looming obstacle of where some of this fossil material might be located, these discoveries open new areas of research and potential locations in which to unearth more evidence of this split.
Is the possibility that our ancestors came from southern Europe a deal breaker for human evolution in general? Absolutely not. Even without the new finds, there is concrete fossil evidence of bipedalism (human ancestors walking on two feet) as far back as six million years, and, as mentioned above, mountains of genetic evidence for human/great ape common ancestry.
Where the human/great ape split took place is, in the grand evolutionary scheme of things, a fairly minor point. As scientists, we go where the evidence leads, and it’s exciting to live in a time when so much important research is being done. Rather than casting doubt on science as a whole, this should give people confidence that scientists are open to having their ideas challenged by new evidence.