Homo heidelbergensis
Homo heidelbergensis is a species of archaic human from the Middle Pleistocene of Europe and Africa, as well as potentially Asia depending on the taxonomic convention used. The species-level classification of Homo during the Middle Pleistocene is controversial, called the "muddle in the middle", owing to the wide anatomical range of variation that populations exhibited during this time. H. heidelbergensis has been regarded as either the last common ancestor of modern humans, Neanderthals, and Denisovans; or as a completely separate lineage.
H. heidelbergensis was described by German anthropologist Otto Schoetensack in 1908 based on a jawbone, Mauer 1, from a sand pit near the village of Mauer — southeast of Heidelberg. It was the oldest identified human fossil in Europe, and Schoetensack described it as an antediluvian race which would eventually evolve into living Europeans. By the mid-20th century, all archaic human taxa were lumped as subspecies of either H. erectus or H. sapiens, with the former evolving into the latter without any coexistence. The species was usually lumped as H. e. heidelbergensis. While its utility was complicated by its definition on a jawbone British physical anthropologist Chris Stringer revived the species in 1983, redefining it as a Euro-African ancestor of modern humans and Neanderthals using namely Kabwe 1, Petralona 1, Bodo, and Arago. These skulls are united mainly by their supraorbital torus anatomy.
H. heidelbergensis may have evolved from H. ergaster possibly following an intense population bottleneck 800,000 to 900,000 years ago. Populations dispersed into Europe by 700,000 years ago, spreading Late Acheulean stone tools, and settlements became more permanent by 500,000 years ago. H. heidelbergensis may have been an active hunter of big game, including straight-tusked elephant and rhinoceros but at least some populations also subsisted significantly on foodplants and small game. Fire does not seem to have been used frequently, but huts and temporary shelters may have been constructed at least around Europe. There are some instances of nondescript etchings on pebbles, as well as modified and heated ochre, which could have been done with symbolic intentions.
Research history
Classification
Raciology
On 21 October 1907, miners recovered a large human mandible about down the Grafenrain sand pit near the village of Mauer — southeast of Heidelberg. German geologists and had earlier characterised the site as diluvial deposits dating to the Tertiary. Mauer 1 was the oldest European human fossil at the time. German anthropologist Otto Schoetensack made the first report of the skull in 1908, classifying it as a new human species, Homo heidelbergensis. After Neanderthals, it was the second-named fossil species in the genus Homo.File:Homo heidelbergensis at Göteborgs Naturhistoriska Museum 8733.jpg|thumb|Cast of Mauer 1 at the Museum of Gothenburg
Schoetensack noted the jaw's exceptionally primitive anatomy with its massive size and lack of chin, yet more modern traits such as small teeth. Therefore, he concluded Mauer 1 must represent an ancient European ancestor, which he claimed was further supported by several ontogenetic developments in Europeans. He also claimed that the many similarities with non-human apes indicate that Mauer 1 lies near the last common ancestor of apes and humans. Based on the mammal fauna of the site, he concluded that the jawbone was of antediluvian age, but he had failed to find Adam.
File:Qafzeh.JPG|thumb|left|The Skhul and Qafzeh hominins were thought to directly descend from Mauer 1.
In 1909, Croatian archaeologist Dragutin Gorjanović-Kramberger recommended renaming Mauer 1 "H. amentalis" as, at that time, every other jaw classified in the genus Homo had at least a weak chin. In 1909, Italian palaeontologist proposed erecting a new genus as "Palaeanthropus heidelbergensis" to recognise its age and primitiveness. German anthropologist suggested "Europanthropus heidelbergensis", and German anthropologist "Rhenanthropus heidelbergensis" for a similar reason. In 1927, Czech-American anthropologist Aleš Hrdlička considered it a European variant of the Java Man "Pithecanthropus erectus". In 1928, German anatomist Franz Weidenreich made a similar opinion. In 1937, American archaeologist and British anatomist Sir Arthur Keith suggested extending "Palaeoanthropus" to any other fossil with many Neanderthal features, with "P. heidelbergensis" as the oldest member. They also included "P. neanderthalensis", "P. ehringsdorfiensis", "P. krapinensis", and "P. palestinensis".
Modern evolutionary synthesis
By the middle of the century with the formulation of modern evolutionary synthesis, the common convention was to relegate all ancient human specimens into the genus Homo, and designate only a single species of Homo at any point in time: H. erectus which evolved into H. sapiens. The many defined species of archaic humans, including heidelbergensis, were generally lumped as subspecies of either H. erectus or H. sapiens. This left H. erectus and H. sapiens considerably polytypic and anatomically variable. In 1963, Russian-American geneticist Theodosius Dobzhansky noted that Middle Pleistocene Western and Eastern Eurasia — the former represented by H. e. heidelbergensis and the Tunisian H. e. mauritanicus; and the latter by the Chinese H. e. pekinensis and H. e. erectus — had significant anatomical and technological differences. He forwarded the possibility that these two groups represent distinct but contemporary species, with H. erectus in the East, and the ancestors of H. sapiens in the West.File:Atlanthropus mauritanicus.jpg|thumb|Theodosius Dobzhansky grouped the Tighennif jaw with Mauer 1.
In 1972, American palaeoanthropologist Bernard Campbell divided Middle Pleistocene H. erectus into two chrono-subspecies ; one group including H. e. heidelbergensis, H. e. mauritanicus, and H. e. pekinensis; and the other the Tanzanian H. e. leakeyi and H. e. erectus. At this point, H. e. heidelbergensis included at least Mauer 1 and the Hungarian Vértesszőlős 2.
Cladistics
In 1974, British physical anthropologist Chris Stringer noted that the Greek Petralona 1 was anatomically more comparable to the Zambian Kabwe 1, Mauer 1, and Vértesszőlős 2 than to East Asian Middle Pleistocene H. erectus. He proposed classifying them as H. s. heidelbergensis — a widespread Euro-African clade, and the last common ancestor of modern humans and Neanderthals. At the time, he was hesitant to revive entire species for fear of recluttering human taxonomy, but in 1983, he proposed classifying them as a unique species as either H. heidelbergensis or H. rhodesiensis, depending on the inclusion of Mauer 1, as the common ancestor of H. sapiens and H. neanderthalensis. The utility of H. heidelbergensis is complicated by its definition on a jaw, which is an uncommon find in Middle Pleistocene deposits, and additionally has few diagnostic traits. Nonetheless, Kabwe 1, Petralona 1, the Ethiopian Bodo cranium, and the French Arago have normally been discussed altogether as representatives of H. heidelbergensis, united most evidently by their brow ridge anatomy.Though H. heidelbergensis became a popular designation, in 2000, American anthropologists Sally McBrearty and Alison S. Brooks argued that H. heidelbergensis should be reserved for only the direct ancestors of Neanderthals in Europe. They recommended reviving H. rhodesiensis to house African Middle Pleistocene fossils they believed were directly ancestral to modern humans. Spanish palaeoanthropologist Juan Luis Arsuaga and colleagues made a similar opinion while studying the Spanish Sima de los Huesos hominins — which comprise the vast majority of the Middle Pleistocene human fossil record. They opted to classify every Middle Pleistocene European fossil as a Neanderthal ancestor under the name H. heidelbergensis, and placed the 1 million year old Spanish H. antecessor as the last common ancestor of modern humans and Neanderthals. Stringer disagreed with the inclusion of the Sima de los Huesos hominins in H. heidelbergensis, preferring to classify them as Neanderthals.
In 2010, American palaeoanthropologists Jeffrey H. Schwartz and Ian Tattersall noted that, while the Euro-African H. heidelbergensis has a wide range of anatomical variation, these specimens may be too derived to represent modern human ancestors — though they could still be closely allied with Neanderthals. In 2011, French anthropologist Aurélien Mounier and colleagues instead extended H. heidelbergensis to encompass Middle Pleistocene specimens all across the Old World, including the Chinese Dali Man and Jinniushan — characterising H. heidelbergensis as an extremely polytypic species and the last common ancestor of modern humans and Neanderthals. They used the 400,000 year old Italian Ceprano Man skull as the "counterpart" of the Mauer 1 mandible to better diagnose the species.
In 2011, Arsuaga and colleagues failed to identify distinctly Neanderthal traits in Mauer 1 — unlike in the Sima de los Huesos hominins and some other Middle Pleistocene Europeans. They recognised two distinct groups occupying Middle Pleistocene Europe: one that was evolving into Neanderthals, and one that was not. In Africa, Stringer noted that some of the specimens he assigned to H. heidelbergensis have similarities with modern humans in the face while others do not.
Multiregionalism
In 2016, Stringer characterised H. heidelbergensis as either the group encompassing the last common ancestor of modern humans and Neanderthals, or a unique branch which eventually became extinct. Either way, H. heidelbergensis would have lived at the same time as more derived morphs. These interconnected derived populations — dispersed across respectively Africa and Europe — seem to have been slowly accruing apomorphies at different rates, which would eventually culminate in respectively anatomically modern humans and classic Neanderthals. Congruently, in 2020, the Kabwe 1 skull was dated to roughly 300,000 years ago, living at the same time as the earliest recognised modern human fossils at the Moroccan Jebel Irhoud site. Late-surviving H. heidelbergensis populations may have interbred with modern humans.While some East Asian Middle Pleistocene fossils have some anatomical similarities to material typically classified as H. heidelbergensis, genetic sequencing of human fossils in the 2010s identified an enigmatic group of archaic humans called the Denisovans — closely related to Neanderthals — dispersed across East Asia. This opened the possibility that these East Asian specimens belong to a different, unique species, such as H. longi.
The species-level classification of Middle Pleistocene humans is still a contentious matter, popularly termed "the muddle in the middle". H. rhodesiensis is usually considered to be a junior synonym of H. heidelbergensis. In 2022, Serbian-Canadian palaeoanthropologist Mirjana Roksandic instead suggested expanding the definition of H. neanderthalensis to include Middle Pleistocene European specimens with Neanderthal traits, and housing African and non-Neanderthal European specimens in H. bodoensis instead of H. rhodesiensis to avoid honouring Cecil Rhodes. She considered H. heidelbergensis too poorly defined to continue using. Her recommendations have been criticised for oversimplifying the archaeological record, and for violating the principle of priority.
In a 2024 interview with Cell Biology Magazine, Stringer expressed doubts with his earlier conceptions of H. heidelbergensis.