“I found Adam!” Construction worker Daniel Hartmann shouted in front of unsuspecting guests at the inn in the German village of Mauer near Heidelberg. Hartmann meant Adam from the Bible, who is said to have been the first human on earth.
It was 1907, and although Hartmann’s discovery was not Adam’s, it was an important one. The German had in his hands the 600,000-year-old jaw of a prehistoric human species, named shortly after Homo heidelbergensis.
Since then, this species has re-emerged in a number of places in Europe, Africa and Asia and has been placed in one of the most important places in the human family tree – as the direct ancestor of our species, Homo sapiens. However, some researchers would like to get rid of Heidelberg disease.
An international research team led by Mirjana Ruksandik of the University of Winnipeg in Canada will clean up the human family tree, which has been in shambles for decades. The tree contains so many species that science disagrees, obscuring the story of our past.
Roksandek suggests deleting some species and assigning a new species to be our direct ancestor.
Grandparents weren’t alone
The broom must pass through the human family tree. The tree takes root at a time when science considered modern man the final product of a long linear evolution from primitive to advanced, from ape to man.
But new discoveries and DNA technology over the past 10-20 years are turning this old view on its head. Our family tree is not a simple straight trunk, but a tangled forest. We once lived alongside many other human species.
Going back only 40,000 years in the family tree, we come across two sister species, the Neanderthals and the mysterious Denisovans. 50,000 years ago, two other species lived alongside us: Homo floresiensis and Homo luzonensis.
About 100,000 years ago, Homo erectus joined us, and 230,000 years ago, Homo naledi raised the total number of human species on the planet to at least six. If we go back further, before the time of our species, more species appear.
This diversity is astonishing, but it also poses a problem for scientists, because exactly how many branches are on the tree and how those branches are connected is open to all kinds of interpretation – and researchers can’t agree.
One of the biggest problems is that such traits of modern humans as a large brain and a flat face did not come one after another in chronological order, as previously thought.
New discoveries show that in some cases our modern traits came before traits that were considered more primitive. Other traits appeared simultaneously, but in two different species.
Almost every discovery has its own set of characteristics, which makes it difficult for researchers to agree on the link between the discoveries. But now, Mirjana Ruksandyk and her colleagues have taken a drastic step toward… solution.
Scientists were dirty
Roksandic wants to get rid of Homo heidelbergensis. Many of the discoveries attributed to species come from a time when researchers believed that human evolution was simple and that the planet was often inhabited by only one human species at a time.
Finds from about the same period as Daniel Hartmann Mauer’s have often been categorized as Homo heidelbergensis – whether or not they resemble Mauer’s discovery.
Researchers cannot agree on a clear definition of the species. There is no unambiguous list of characteristics to determine if a new find belongs to heidelbergensis.
The same goes for another species, Homo rhodesiensis, which has been a nuisance to researchers since it was named in 1921.
In the new Roksandic study, both heidelbergensis and rhodesiensis fall off the family tree. The scientist and her colleagues examined numerous fossils dating back 200,000-700,000 years, many of which have been attributed to only these two species.
The conclusion is that all fossils should be given a different name.
Several European finds of Heidelberg, including the jaw from Mauer, are now early Neanderthals, according to Ruksandek. It is likely that a number of Asian finds belong to a new species, for which the Roksandic team has not yet given a name.
However, other researchers refer to several Asian fossils as Homo longi. It may also turn out that some finds from Asia are a sister species of Neanderthals, Denisovans, which we know only from small bone fragments.
Asian fossils are certainly part of human evolution, but Ruksandik’s main contribution to the story is based on African finds.
The new species are our ancestors
Based on an Ethiopian skull previously named either Homo heidelbergensis or rhodesiensis, the Roksandic team came up with a new species, Homo bodoensis — named after Bodo D’ar, where the skull was found.
Several other finds from Africa, and possibly another from Italy, have also been added to the species that lived about 300,000 to 600,000 years ago.
The new species is better identified than Homo heidelbergensis, and this will make it easier to identify new discoveries. A more straightforward definition will also show how species are related to each other in the family tree.
And according to Roksandic, Homo bodensis has a very special place in our family tree. The species shares with us a number of traits that are not found in other species—not even in our closest relatives, Neanderthals.
This likely means that Neanderthals were the direct ancestor of Homo sapiens. This gives scientists insight into a crucial period in human evolution.
New species get a mixed reception
Homo bodensis is now listed as an official species on ZooBank: An International Register of All Species. But this does not mean that all researchers will adopt the species and use the new definitions in their work.
Once the new study was published, Homo bodensis was criticized. Some scientists say it is unusual to base a new species on an old find. Others say we don’t need to abolish Heidelbergensis. Others find it difficult to see how a new species can help regulate the chaos.
However, this species has been warmly received by many researchers. By the way, no one disputes the idea behind Homo bodoensis: that more clarity is needed about the fossils in the family tree.
Whether or not the new species catches on, Ruksandyk and her colleagues have identified a number of pain points and sparked debate about the search for our ancestors.
Scientists around the world will now think twice before classifying a fossil as heidelbergensis – they are forced to be more thorough in their research.
Furthermore, Heidelbergensis Daniel Hartmann of Mauer has become the subject of a completely different discussion. This discovery was found in a chest at the University of Heidelberg, although the Mayor of Mauer has been trying for years to recover it.
The village wants to build a museum of ancient jaws – because in Mauer the human race Homo heidelbergensis still has its place.
