Homo heidelbergensis: The Mauer Jaw and Europe's Early Humans

Homo heidelbergensis is an extinct species of early human named in 1908 from a single lower jaw found in a sand pit at Mauer, near Heidelberg in south-western Germany. Dated to about 609,000 years ago, the Mauer jaw is one of the oldest human fossils in central Europe. The species it defines has become a central, and much debated, piece in the puzzle of how Neanderthals and modern humans came to be.

The discovery in the Mauer sand pit

The village of Mauer lies about 10 kilometres south-east of Heidelberg, in a former loop of the Neckar River. In the late 19th century its sand pits were famous for fossils of Ice Age animals, including the straight-tusked elephant, rhinoceroses, horses and big cats. Otto Schoetensack, a scholar at the University of Heidelberg, had for years asked the owners of the Grafenrain pit to look out for any human remains.

On 21 October 1907 a worker named Daniel Hartmann found a massive lower jaw at a depth of about 24 metres. It had broken in two, but almost all its teeth were present. The pit owner informed Schoetensack, who studied it intensively and in 1908 published a monograph naming a new species, Homo heidelbergensis.

What the jaw shows

The Mauer mandible is strikingly robust. Its body is thick and deep, the branch rising to the jaw joint is very broad, and there is no chin. Seen in isolation, it could almost belong to a large ape. Yet the teeth tell a different story: they are relatively small and arranged much like those of modern people, with no large projecting canines.

This combination of an archaic jaw and human-like teeth convinced Schoetensack that he had an early member of the human genus. Because the specimen is the first fossil to have received the name, the Mauer jaw, catalogued as Mauer 1, is the holotype of the species: all other fossils assigned to Homo heidelbergensis are compared with it. No stone tools have been found reliably associated with the jaw at Mauer.

Dating the find

For most of the 20th century the age of the Mauer jaw was estimated from the animal fossils found with it, which pointed to an early part of the Middle Pleistocene, perhaps half a million years ago or more. In 2010 a team led by Günther Wagner published radiometric dates from the sands, using electron spin resonance combined with uranium-series dating on mammal teeth, and infrared luminescence on the sediment grains.

The results gave an age of about 609,000 years, with an uncertainty of around 40,000 years. That places the Mauer human in a relatively warm phase within the long sequence of Ice Age climate swings, when forests and large herbivores flourished along the Neckar.

Who belongs to Homo heidelbergensis?

Over the 20th century the name was gradually applied to many other fossils from roughly 700,000 to 200,000 years ago. In Europe these include the skull from Petralona in Greece, the face from Arago Cave at Tautavel in France, and the shin bone and teeth from Boxgrove in England, about half a million years old. In Africa the skulls from Bodo in Ethiopia and Kabwe in Zambia are often included. Some researchers also place certain Chinese fossils in the group.

These humans had brains of roughly 1,100 to 1,300 cubic centimetres, close to the lower end of the modern range, combined with long, low skulls and heavy brow ridges. They are associated with Acheulean hand axes and, in Europe, with hunting of large animals. At Boxgrove, butchered horse bones suggest skilled hunting, and the wooden spears from Schöningen in Germany, dated to roughly 300,000 to 200,000 years ago, show that such weapons were in use.

Life in Middle Pleistocene Europe

The world of the Mauer human was very different from today’s Germany. The animals found in the same sands, among them the straight-tusked elephant, rhinoceroses, early bison, wild horses, deer, beavers, lions and bears, point to a mosaic of woodland and open river meadows during a relatively mild interval. Colder phases, when ice sheets advanced across northern Europe, repeatedly pushed human groups south or emptied whole regions.

Evidence from sites of similar age elsewhere in Europe fills in the picture. People made carefully shaped hand axes and flake tools, butchered large carcasses and probably shared food within small groups. Whether they could make fire at will in this period is uncertain: clear hearths only become common in the European record after about 400,000 years ago. Population density was certainly very low, and many early attempts to settle northern Europe may have ended in local extinction.

Because only one jaw has been found at Mauer, nothing can be said directly about the individual’s height or build. Studies of the teeth, which show moderate wear, suggest a young adult, and the jaw is often interpreted as male because of its size, though this cannot be proved.

A muddle in the middle

The species has become controversial, part of what palaeoanthropologists call the “muddle in the middle” of human evolution. Ancient DNA from the 430,000-year-old fossils of the Sima de los Huesos in Spain showed that those people were already on the Neanderthal lineage. If European fossils of similar age are early Neanderthals, they cannot also be the common ancestor of Neanderthals and modern humans.

Some scholars therefore restrict Homo heidelbergensis to a narrower group, or treat it as a label for a widespread and varied population that gave rise to Neanderthals in Europe and to Homo sapiens in Africa. Others prefer the older name Homo rhodesiensis for the African fossils, and in 2021 a team proposed a new name, Homo bodoensis, for them, a suggestion that many colleagues did not adopt. Genetic estimates place the split between the Neanderthal and modern human lineages somewhere around 550,000 to 750,000 years ago, close to the age of the Mauer jaw itself.

Myths and facts

The name “Heidelberg Man” can give the impression that a whole skeleton was found. In fact the species rests on a single jaw, and much of what is said about its body comes from other fossils assigned to it later. It is also sometimes presented as a settled direct ancestor of modern humans; in reality, this is one hypothesis among several.

Timeline

• c. 609,000 years ago: The Mauer individual dies and is buried in river sands of the Neckar.
• 1907, 21 October: Daniel Hartmann finds the jaw in the Grafenrain sand pit.
• 1908: Otto Schoetensack names Homo heidelbergensis.
• 1960: The Petralona skull is found in Greece.
• 1971: The Arago 21 face is found at Tautavel in southern France.
• 1993-1996: Excavations at Boxgrove, England, yield a shin bone and teeth.
• 2010: Radiometric dating gives an age of about 609,000 years.
• 2016: Nuclear DNA from Sima de los Huesos reshapes debate over the species.

Why it matters

The Mauer jaw remains a key reference point for Europe’s earliest well-dated humans. The species it defines sits right at the junction where the paths leading to Neanderthals and to ourselves diverged, which is why its name, its membership and its meaning are argued over so intensely. Whatever its final status, Homo heidelbergensis marks the stage when large-brained, skilled human hunters became established across Africa and Europe.