The lower jaw of Homo heidelbergensis was an isolated find and has long been overshadowed by other spectacular early human finds. Homo heidelbergensis is regarded as the last common ancestor of Neanderthals and Homo sapiens, and so is a central part of the debate on modern human origins.
On the evening of 21st October 1907, Daniel Hartmann, a gravel pit worker known as ‘Sanddaniel’, walked into the Hochschwender pub in the village of Mauer near Heidelberg and announced that he had found “Adam”. What he had found in the Grafenrain sand pit on the river Elsenz near Heidelberg was an almost complete, fairly robust human jaw that appeared to be very old indeed. The palaeontologist Professor Otto Schoetensack from the University of Heidelberg who had previously visited the Grafenrain pits in search of glacial fossils was contacted the following day. Schoetensack described the find in a monograph entitled “Der Unterkiefer des Homo heidelbergensis aus den Sanden von Mauer bei Heidelberg” (The lower jaw of the Homo heidelbergensis from the Mauer sands near Heidelberg”) published in 1908. Schoetensack realised almost immediately how important the discovery was and believed the Mauer mandible to be older than the Neanderthals. Neanderthals were classified as such based on a specimen discovered in the Neander Valley near Düsseldorf (Germany) in 1856. Following the discovery of this Neanderthal type specimen, other previously discovered fossils were also (retrospectively) classified as Neanderthal.
The jaw of the prehistoric man from Heidelberg, the valuable type specimen, has been dated to around 600,000 years ago and is kept in a safe in the Institute of Earth Sciences (formerly, the Institute of Geology and Palaeontology) at the University of Heidelberg. However, visitors can see a detailed replica of the fossil jaw in the institute’s museum as well as in the small primeval world museum in Mauer town hall. No further remains of the “Heidelberg Man”, as Homo heidelbergensis is also known, have been discovered at the site despite intensive searches. However, huge quantities of single rhino, elephant, lion and hippo bones have been found in the Grafenrain sand pit and not so long ago human fossils were found in the village of Bilzingsleben near the Kyffhäuser mountains; these fossils are geologically more recent than the Mauer mandible, but have nevertheless been assigned to the same species. Well-preserved hunting spears and animal skeletons have also been discovered in the village of Schöningen (close to Helmstedt), suggesting that their owners were excellent hunters. Illustrations of these finds are displayed in the primeval world museum in Mauer.
In the 1890s, Dutch geologist Eugène Dubois excavated the skull roof and thigh bone of a human specimen on Java, which he classified as a “species in between humans and apes”. He called it Pithecanthropus erectus (originally Anthropopithecus), i.e. an “ape-human that stands upright”. However, many of his peers disagreed with Dubois’ interpretations, which is why the 1907 “Heidelberg Jaw” was long seen as the earliest evidence of human evolution.
Palaeoanthropologists seem to be constantly embroiled in polemic, even according to the standards of the scientific world. Could this be because their research objects cause a stir that spills over into the non-scientific realm, often putting the researchers in the limelight? Could it also be because palaeoanthropologists are exposed to attacks from the church and from religious fundamentalists of all creeds? In the first half of the 20th century, the passion of the disputes was often not only stoked by the vanity and vulnerability of the researchers, but also by nationalistic and racist prejudices which seem odd to us today.
A few years after the discovery of the Mauer mandible, a spectacular discovery in a gravel pit near the village of Piltdown in the south of England hit headlines around the world. It consisted of fragments of a human skull with an ape-like lower jaw. Primitive stone tools as well as rhinoceros and elephant bone fragments were discovered alongside it. It seemed that the perfect missing link Darwin alluded to in his epochal oeuvre 40 years previously had finally been discovered. The outpouring of joy was tremendous because, at the height of Anglo-German rivalry in the period immediately preceding WWI, the British had outperformed the Germans, including in the field of human origin. The ironic term “Homo britannicus” (the official name of the species was Eoanthropus dawsoni, after its collector, Charles Dawson) suggested that at least one patriot truly believed that mankind was of British origin.
The Piltdown Man was “an audacious fake and a sophisticated scientific fraud” (quoted from the website of the Natural History Museum in London). The skull fragments actually came from a modern human and had been artificially stained to match the surrounding gravel; the lower jawbone and canine of an orang-utan were also found. From the outset, some scientists had expressed scepticism at the find, but it was not until 1952 – approximately 40 years after its alleged discovery – that the forgery was discovered by Kenneth Oakley, then a geoarchaeologist at the Natural History Museum, after he had carried out chemical analyses of the finds. He is credited with restoring the tarnished image of the world-famous museum. Now, a hundred years after the “discovery” of the skull fragments, this criminal case still occupies the minds of scientists around the world: what roles did those involved in the fraud play, including famous figures like the Jesuit priest Teilhard de Chardin? What were the motives behind the fraud? In a recent publication, Professor Chris Stringer, head of research of the “Human Origins” department at the Natural History Museum, presents the current view of the scandal and a new research programme aimed at finally unravelling the mystery of Piltdown Man using state-of-the-art DNA analysis, spectroscopy, radiocarbon- and isotope analysis methods (Nature 492, 177-179, 13th December 2012: “The 100-year mystery of Piltdown Man“).
Beyond a doubt, the scandal had damaged the reputation of science, but it did not succeed in stopping the progress of research. In the decades after WW1, numerous discoveries “shed light on the origin of man” (as Darwin once famously wrote). Racial prejudices nevertheless dominated human thinking for quite some time. This led, for example, to an American anthropologist saying in 1962: “If Africa was the cradle of mankind, it was only an indifferent kindergarten. Europe and Asia were our principal schools” (C. Stringer: The Observer, 19th June 2011). It was only modern DNA analyses that helped the thesis that mankind actually originated in Africa to gain ground.
The first humans to leave Africa belonged to the species Homo erectus, named after the first specimen of Homo erectus discovered (and later confirmed as a true find) in Java by Eugène Dubois in 1891. The earliest Homo erectus fossils, dating to around 1.8 million years ago, were discovered in East Africa. It is assumed that Homo erectus quickly migrated from Africa to West Asia (Dmanisi in Georgia) and then moved on to China and Indonesia where Homo erectus descendants lived up until at least 200,000 years ago. It is generally agreed that Homo erectus originates from more ancient African hominids (Homo habilis or Australopithecus); however, the details of their phylogenetic relationships remain highly controversial and are a central part of the debate on modern human origins.
For a long time, all hominids of the pre-Neanderthal era found in Eurasia were classified as Homo erectus. The Mauer mandible was therefore initially classified as Homo erectus heidelbergensis, a term still used by the Heidelberg-based Museum of Geology and Palaeontology. Many anthropologists are since using a new, broader nomenclature. The original H. erectus who lived approximately 700,000 years ago evolved into a new human species with a much bigger brain who used well-manufactured stone tools (known as the Acheulian culture) which, in a second propagation wave (out of Africa II theory), subsequently migrated to southern Europe, including Germany and England. All representatives of this more advanced human species are classified as Homo heidelbergensis based on the Mauer type specimen. Their robust build and excellent hunting tools appeared to be well suited to dealing with the climate fluctuations in Europe. H. heidelbergensis hominids evolved into the Neanderthals approximately 250,000 years ago.
The Homo heidelbergensis populations that remained in Africa (most probably the great majority) evolved into the ancestors of modern humans; however, little information is available about their evolution. Humans classified as H. heidelbergensis lived in Ethiopia, Zambia and South Africa around 600 – 500,000 years ago; around 200,000 years ago, anatomically modern humans lived in Ethiopia and have therefore been recognised as Homo sapiens. These Homo sapiens specimens are part of the third propagation wave (out of Africa III or recent out of Africa theory), which occurred less than 100,000 years ago. They colonised Europe around 45,000 years ago and eventually went on to colonise the whole world.
According to current scientific knowledge, the aforementioned scenario is plausible but not undisputed. New unexpected discoveries can change the picture tremendously, for example the Homo erectus fossil found in Dmanisi in Georgia, the dwarfish Flores Man (Homo floresiensis) dating to around 17,000 years ago and the Denisova Man from south Siberia identified from the DNA analysis of a finger bone. Although multiple new human fossils have been discovered over the last decades, there are still big gaps in the fossil evidence regarding the alleged evolution of humans. An even bigger problem is that only fragments have been discovered: a few skull pieces here, and an arm bone, teeth, a cheekbone or a lower jawbone at a different site. This leaves room for different interpretations and controversy. Researchers are therefore diligently and patiently searching for further fragments at known discovery sites in the assumption that the sites harbour more information about the fossils. The “Isotope Geochemistry” research group led by Dr. Bernd Kober at the Institute of Earth Sciences at the University of Heidelberg, for example, is specifically focused on the Mauer discovery site and is using a state-of-the-art thermion mass spectrometer to analyse the Grafenrain sand pit where Daniel Hartmann discovered his “Adam” in 1907.