Peking Man

Peking Man also played a vital role in the restructuring of Chinese identity following the Chinese Communist Revolution, and it was used to introduce the general populace to Marxism and science. Early models of Peking Man society were compared to communist or nationalist ideals, leading to discussions on primitive communism and polygenism (that Peking Man was the direct ancestor of Chinese people). This produced a strong schism between Western and Eastern interpretations of the origin of modern humans, especially as the West adopted the Out of Africa theory in the late 20th century, which described Peking Man as an offshoot in human evolution. Though Out of Africa is now the consensus, Peking Man interbreeding with human ancestors is still discussed.

Peking Man characterises the classic H. erectus anatomy. The skull is long and heavily fortified, featuring an inflated bar of bone circumscribing the crown, crossing along the brow ridge, over the ears, and connecting at the back of the skull; as well as a sagittal keel running across the midline. The bone of the skull and the long bones is extremely thickened. The face is protrusive (midfacial prognathism), the eye sockets are wide, the jaws are robust and chinless, the teeth are large, and the incisors are shovel-shaped. Brain volume ranged from 850 to 1,225 cc (52 to 75 cu in), for an average of just over 1,000 cc (61 cu in)—within the range of variation for modern humans. The limbs are broadly anatomically comparable to those of modern humans. H. erectus in such northerly latitudes may have averaged roughly 150 cm (4 ft 11 in) in height, compared to 160 cm (5 ft 3 in) for more tropical populations.

Peking Man lived in a cool, predominantly steppe, partially forested environment, alongside deer, rhinos, elephants, bison, buffalo, bears, wolves, big cats, and other animals. Peking Man fossils appear intermittently in Zhoukoudian deposits dating as far back as 800,000 years ago to as recently as 230,000 years ago, but the precise chronology is unclear. This spans several cold glacial and warm interglacial periods. The cultural complexity of Peking Man is fiercely debated. If Peking Man was capable of hunting (as opposed to predominantly scavenging), making clothes, and controlling fire, the population would have been well-equipped to survive frigid glacial periods. If not, the population would have had to retreat southward and return later. It is further disputed if Peking Man inhabited the cave, or was killed by giant hyenas (Pachycrocuta) and dumped there. Over 100,000 pieces of stone tools have been recovered from Zhoukoudian. Those pieces have been mainly debitage (wastage), but also include many simple choppers and flakes, and a few retouched tools such as scrapers and possibly burins.

Taxonomy

Research history

Discovery

To aid the China Geological Survey's efforts to map out economically relevant deposits, the Geological Survey of Sweden sent the Swedish economic geologist Johan Gunnar Andersson to China in 1914. Andersson soon also began collecting archaeological finds and "dragon bones", as well as documenting Chinese mythology. In 1918, while in Beijing (then referred to in the West as Peking), he was pointed towards a potentially interesting fossil deposit in the mining town of Zhoukoudian in the Fangshan District, about 50 kilometres (31 miles) southwest, by the American chemistry teacher John McGregor Gibb. When Andersson visited a month later, he was directed towards an old limestone quarry which the locals called Chi Ku Shan ('Chicken Bone Hill'). They believed the many rodent fossils found there belonged to chickens stolen by a malevolent group of foxes that had turned into evil trickster spirits and drove a man insane.

Andersson left China to work on other projects, but returned in 1921 with the prominent American palaeontologist Walter W. Granger and the Austrian palaeontologist Otto Zdansky, a recent graduate of the Palaeontological Museum of Uppsala University. Andersson decided that the Chi Ku Shan locality would be an excellent training ground for Zdansky before the pair moved on to excavating Hipparion (horse) fossils in Henan. They were advised by a local that more interesting "dragon bones" could be found at a nearby fissure in a limestone cliff, later named Longgushan ('Dragon Bone Hill') locality. That same year, Zdansky found the first fossil (specimen PMU M3550)—a human tooth—in the site, but he did not report it to Andersson. While studying the Zhoukoudian material in Uppsala, Zdansky identified another human tooth, and reported his find (which he cautiously labelled as Homo sp.?) to his professor and mentor Carl Wiman, who informed Andersson in 1926.

As part of his world tour, the crown prince of Sweden (and the chairman of the Swedish China Research Committee, Andersson's benefactor) Gustaf VI Adolf visited Beijing on 22 October 1926. At a meeting planned for the prince, Andersson presented lantern slides of Zdansky's fossil teeth. He was able to convince his friend, the Canadian palaeanthropologist Davidson Black (who worked for the Peking Union Medical College, which was funded by the Rockefeller Foundation), the Chinese geologist Weng Wenhao (the head of the China Geological Survey), and the prominent French palaeoanthropologist Pierre Teilhard de Chardin to jointly take over study of Zhoukoudian. Andersson returned to Sweden to become the founding director of the Museum of Far Eastern Antiquities, Stockholm. In the press coverage immediately after the meeting, the German-American geologist Amadeus William Grabau for the first time publicly used the phrase "Peking Man" to refer to Zdansky's fossil teeth.

In 1927, Black was preoccupied with his duties to the college, so Andersson and Wiman sent one of Wiman's students, Anders Birger Bohlin, to oversee excavation beginning on 16 April. On 16 October, Bohlin extracted another fossil human tooth (specimen K11337), which Black made the holotype of a new genus and species called Sinanthropus pekinensis a few weeks later, accrediting the authority to both himself and Zdansky. This was the first anthropologically relevant find for nearly a year, and Teilhard questioned whether Peking Man was actually a human or some animal carnivore. According to the biological anthropologist Noel T. Boaz and the palaeoanthropologist Russell Ciochon, Black's decision to so quickly name a new genus may have been politically motivated—to secure further funding of the site. That year, Weng drafted an agreement with all Zhoukoudian scientists at the time that the Zhoukoudian remains would remain in China. In 1928, the Chinese government similarly clamped down on the exportation of Chinese artefacts and other archaeologically relevant materials to the West for study, viewing it as archaeological looting; foreign scientists were instead encouraged to research these materials within China. In 1929, Black persuaded the Peking Union Medical College, the China Geological Survey, and the Rockefeller Foundation to found and fund the Cenozoic Research Laboratory and ensure further study of Zhoukoudian.

On 2 December 1929, the Chinese anthropologist Pei Wenzhong discovered a fairly complete skullcap. Zhoukoudian proved to be a valuable archaeological site, with a preponderance of human fossils, stone tools, and potential evidence of early fire use, becoming the most productive Homo erectus site in the world. An additional four rather complete skullcaps were discovered by 1936, three of which were unearthed over an 11-day period in November 1936, overseen by the Chinese palaeoanthropologist Jia Lanpo. Excavation employed from 10 to over 100 local labourers depending on the stage, who were paid five or six jiao per day, in contrast to local coal miners who received a pittance of 40 to 50 yuan annually. According to the historian Sigrid Schmalzer, Zhoukoudian employed some of the biggest names in Western and Chinese geology, palaeontology, palaeoanthropology, and archaeology, and facilitated an important discourse and collaboration between these two civilisations. After Black's sudden death in 1934 from his congenital heart defect, the Jewish German anatomist Franz Weidenreich, who had fled Nazi Germany, was selected by the Rockefeller Foundation to continue Black's work.

Loss of specimens

Excavation of Zhoukoudian began to stall after the Marco Polo Bridge incident on 7 July 1937 and the outbreak of the Second Sino-Japanese War. Weidenreich had two crates made to store the Peking Man fossils, and transferred them from the Peking Union Medical College to an American bank vault to safeguard them from Imperial Japanese forces. They were soon returned to the college and stored in a safe in Weidenreich's office, where Weidenreich worked with technicians and artists to make plaster casts and detailed illustrations for his monograph describing the fossils. As the war progressed, Weng and Weidenreich unsuccessfully tried to convince the head of the college, Henry S. Houghton, to authorise a transfer of the Peking Man fossils to the United States for safekeeping. Houghton dismissed Weidenreich in 1941, who took the casts and research notes with him to the American Museum of Natural History in New York City with funding from the Rockefeller Foundation.

By September 1941, Weng and the president of the Rockefeller Foundation Raymond B. Fosdick had persuaded the U.S. embassy to authorise the transfer of the Peking Man fossils. Representing at least 40 different individuals, the fossils were put into two wooden footlockers and were to be transported by the United States Marine Corps from the Peking Union Medical College to the SS President Harrison which was to dock at Qinhuangdao Port (near the Marine base camp Camp Holcomb), and eventually arrive at the American Museum of Natural History. En route to Qinhuangdao, the ship was attacked by Japanese warships and ran aground. Though there have been many attempts to locate the footlockers—including by offers of large cash rewards—it is unknown what happened to them after they left the college on 4 December 1941.

Rumours about the fate of the fossils range from being on board a sunken ship (such as the Japanese Awa Maru) to being ground up for traditional Chinese medicine. The affair also provoked allegations of robbery against Japanese and American groups, especially during the Resist America, Aid Korea Campaign in 1950 and 1951 to promote anti-American sentiment during the Korean War. U.S. Marine corporal Richard Bowen recalled finding a box filled with bones one night in 1947 while digging a foxhole next to some stone barracks in Qinhuangdao. This happened during the Chinese Civil War, during a siege of the city by the Communist Eighth Route Army, who were under fire from Nationalist gunboats. According to Wang Qingpu, the author of a report for the Chinese government on the history of the port, if Bowen's story is accurate, the most probable location of the fossils is 39°55′4″N 119°34′0″E / 39.91778°N 119.56667°E, underneath roads, a warehouse, or a parking lot.

Excavation of the Zhoukoudian was so well documented that the loss of the original specimens did not greatly impact their study. According to Teilhard: "The Sinanthrope has been dated, described, measured, x-rayed, drawn, photographed and cast in plaster down to the last fossa, crista and tubercle .... The loss is more a matter of sentiment than a true tragedy for science." Four of the teeth from the original excavation period are still in the possession of the Palaeontological Museum of Uppsala University.

Mao and post-Mao eras

Excavation of Zhoukoudian halted from 1941 until the conclusion of the Chinese Civil War in 1949. Field work took place in 1949, 1951, 1958–1960, 1966, and 1978–1981. In 2004, Boaz noted that—given the meticulousness of the dig teams, going so far as to sieve out unidentifiable fragments as small as 1 cm (0.39 in) long—excavation of Zhoukoudian is generally considered to be complete.

Every bone, bone fragment or tooth, however small, is picked up and put aside in a basket which each technician has ready for this purpose. A group of technicians always works together, so that practically each lump of earth will be scrutinized. Nevertheless, the loose earth, too, is afterwards transported to a special place and passed through a fine sieve.

— Franz Weidenreich, 1941

Throughout the Mao era, but especially in 1950 and 1951, Peking Man took on a central role in the restructuring of Chinese identity under the new government, specifically in an attempt to link the ideology of the Chinese Communist Party with human evolution. Peking Man was taught in educational books for all levels, popular science magazines and articles, museums, and at lectures given in workspaces, including factories. This campaign was primarily done to introduce the general populace (including those without advanced education) to Marxism, as well as to overturn widespread superstitions, traditions, and creation myths. Nonetheless, research was constricted as scientists were compelled to fit new discoveries within the frame of Marxism. In 1960, the Cenozoic Research Laboratory was converted into an independent organisation known as the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), a division of the Chinese Academy of Sciences, to better support excavation of Zhoukoudian. It was headed by Pei, Jia, and the Chinese palaeoanthropologist Yang Zhongjian.

During the Cultural Revolution from 1966 to 1976, all intellectuals, including scientists, came under persecution, and among other things were conscripted into manual labour as part of a campaign to turn "intellectuals into labourers and labourers into intellectuals", which impeded research. Though palaeoanthropology was still able to continue, the field became much less important to the Chinese government with its new resolve to become economically independent, and popular science topics switched from Peking Man and human evolution to production-related matters.

The United Nations declared the Zhoukoudian Peking Man site to be a World Heritage Site in 1987, and custody of the site was handed over from the IVPP to the city of Beijing (which has greater resources) in 2002.

The productivity of Zhoukoudian elicited strong palaeoanthropological interest in China, and 14 other H. erectus sites have since been discovered across the country as of 2016 in the Yuanmou, Tiandong, Jianshi, Yunxian, Lantian, Luonan, Yiyuan, Nanzhao, Nanjing, Hexian, and Dongzhi counties.

Age and stratigraphy

The Zhoukoudian Peking Man Site currently sits 128 m (420 ft) above sea level. The fossil-bearing sediments are divided into 27 localities, and Peking Man is known from Locality 1 (Dragon Bone Hill). This 40 m (130 ft) deep locality is further divided into 17 layers (Layer 1 is the highest and youngest), of which fossils are found above Layer 13, and Peking Man from Layers 10–3. The fossil-bearing regions can also be organised into Loci A–O. Major stone tool accumulations occur in Layers 3 and 4, and the tops of Layers 8 and 10. The animal fossils in the locality suggest it dates to the Middle Pleistocene.

There have been many attempts to more finely tune the date of each layer, starting in the late 1970s. In 1985, the Chinese scientist Zhao Shusen proposed the chronology: 700,000 years ago for Layer 13; 500,000 years ago for Layer 10; and 230,000 years ago for Layers 3. Though these timeframes are generally agreed upon, the exact date of each layer is subject to debate. In 2004, Shen Chengde and colleagues argued that Layer 3 was deposited 400,000 to 500,000 years ago; and Layer 10 between 600,000 and 800,000 years ago, during a mild glacial period.

The earliest H. erectus fossils in all of China, Yuanmou Man, may date to 1.7 million years ago, though stone tools from the Shangchen site in Lantian, central China, could extend the occupation of the region as far back as 2.12 million years ago.

Classification

Background

While Charles Darwin had hypothesised in his 1871 Descent of Man that humans most likely evolved in Africa, many late-19th century evolutionary naturalists postulated that Asia was the birthplace of humankind, as it is midway between all continents via land routes or short sea crossings, providing optimal dispersal routes throughout the world. Among them was Ernst Haeckel, who argued that the first human species (which he proactively named "Homo primigenius") evolved on the now-disproven hypothetical continent "Lemuria" from a genus he termed "Pithecanthropus" ('ape-man'). "Lemuria" had supposedly sunk below the Indian Ocean, so no fossils could be found to prove this. Nevertheless, Haeckel's model inspired Dutch scientist Eugène Dubois to join the Royal Netherlands East Indies Army and search for the "missing link" in Java. He found a skullcap and a femur (Java Man) which he named "P. erectus" (using Haeckel's hypothetical genus name) and unfruitfully attempted to convince the European scientific community that he had found an upright-walking ape-man; they dismissed his findings as some kind of malformed non-human ape.

In regard to the ancestry of Far Eastern peoples, the French orientalist Albert Terrien de Lacouperie advanced the now discredited theory of Sino-Babylonianism, which placed the origin of Chinese civilisation in the Near East, namely Babylon. Terrien de Lacouperie argued, according to historical race concepts and the idea of social degeneration, that the Chinese peoples had regressed compared to the superior races of Europe. This came under fire by the time Peking Man was discovered, when China was in the midst of the New Culture Movement and surging nationalism subsequent to the 1911 Revolution that ended the Qing dynasty and established the Republic of China. These ideologies not only aimed to remove imperialist influences, but also to replace ancient Chinese traditions and superstitions with western science to modernise the country and lift its standing on the world stage to that of Europe.

"Out of Asia" theory

Unlike previously discovered extinct human species, notably the Neanderthal and Java Man, the Peking Man was readily accepted into the human family tree. In the West, this was aided by a popularising hypothesis for the origin of humanity in Central Asia, championed primarily by the American palaeontologist Henry Fairfield Osborn and his apprentice William Diller Matthew. They believed that Asia was the "mother of continents", and that the rising of the Himalayas and Tibet and subsequent drying of the region forced human ancestors to become terrestrial and bipedal. They also believed that populations which retreated to the tropics—namely Dubois' Java Man and the "Negroid race"—substantially regressed. This required them to reject Sir Raymond Dart's far more ancient South African Taung child (Australopithecus africanus) as a human ancestor when he described it in 1925, favouring Charles Dawson's 1912 hoax "Piltdown Man" from Britain.

The Peking Man, with a brain volume much larger than that of living apes, was used to further invalidate African or European origin models. Peking Man's importance in human evolution was championed by Grabau in the 1930s, who (much like Osborn) contended that the lifting of the Himalayas caused the emergence of proto-humans ("Protanthropus") in the Miocene, who then dispersed during the Pliocene into the Tarim Basin in Northwestern China where they learned to control fire and make stone tools. "Protanthropus" then reached Eastern China and evolved into "Sinanthropus"; and from there went out to colonise the rest of the Old World, where it evolved into "Pithecanthropus" in Southeast Asia, "Eoanthropus" (Piltdown Man) in Europe, and Homo (Kanam Mandible) in Africa. Citing degeneration theory, Grabau believed that "Pithecanthropus" and African Homo had regressed to a more primitive state. To explain the paucity of stone tools in Asia compared to Europe (an apparent contradiction if humans had occupied Asia for longer), he also stated that Pleistocene Central Asia was too cold to permit back-migration by early modern humans or Neanderthals (primitive Homo) until the Neolithic. The Central Asia model was the leading consensus of the time.

Peking Man became an important matter of national pride, and was used to extend the antiquity of the Chinese people and the occupation of the region to 500,000 years ago, with discussions of human evolution becoming progressively Sinocentric even in Europe. In the 1930s, Weidenreich began arguing that Peking Man was ancestral to the "Mongoloid race", forwarding his polycentric hypothesis, where local populations of archaic humans evolved into the local modern humans, as opposed to every modern population sharing an anatomically modern ancestor (polygenism). Other scientists working on the site made no such claims. The sentiment that all Chinese ethnic groups—including the Han, Tibetans, and Mongols—were indigenous to the area for such a long time became more popular during the Second Sino-Japanese War and the occupation of China by Japan. By the Mao era, Peking Man was ubiquitously heralded as a human ancestor in China.

"Sinanthropus"

Black classified the Peking Man material in 1927 as a new genus and species—"Sinanthropus pekinensis"—based on only three teeth. Initially, palaeoanthropologists assumed that expansion of the braincase was the first major innovation in human evolution away from apes. Consequently, because he characterised Peking Man as a human ancestor, Black initially believed that Peking Man would be more similar to Piltdown Man (with a big brain and modern skullcap but an apelike jaw) than Java Man (which at the time was characterised as a giant gibbon by Dubois). When the first Peking Man skullcap was discovered in 1929, Black and his mentor Sir Grafton Elliot Smith noted "a curious blend of characters" between Peking Man, Java Man, and Piltdown Man. They were unsure how to resolve these relationships.

Weidenreich, on the other hand, dismissed Piltdown Man as a chimera of a modern human skull and an orangutan jaw in 1923, and also argued that Java Man had a humanlike body plan. In 1935, he claimed the differences between Peking Man and Java Man, "can be due at most to racial variation". Following the German-Dutch palaeontologist Gustav Heinrich Ralph von Koenigswald's further Java Man discoveries in Mojokerto and Sangiran, von Koenigswald and Weidenreich declared in a 1939 paper that Java Man and Peking Man are, "related to each other in the same way as two different races of present mankind, which may also display certain variations in the degree of their advancement."

In 1940, Weidenreich likewise suggested that, if Peking Man ("Sinanthropus pekinensis") and Java Man ("Pithecanthropus erectus") are ancestral to different modern human populations (classified into several subspecies of Homo sapiens), then they should be subsumed under Homo as subspecies of the same pre-modern species as H. erectus pekinensis and "H. e. javanensis", respectively. Nonetheless, Weidenreich continued using "Sinanthropus" (and "Pithecanthropus") until his death in 1948 because he saw it "just as a name without any 'generic' or 'specific' meaning, or in other words, as a 'latinization' of Peking Man." In 1945, the British anatomist Wilfrid Le Gros Clark argued that, in accordance with nomenclature codes, the correct name should be "Pithecanthropus pekinensis". Still, especially after the Holocaust, Weidenreich and many of his colleagues desired to reform anthropology away from its fixation on racial distinctness and purity. Weidenreich discussed applying the burgeoning field of genetics to physical anthropology with namely Theodosius Dobzhansky and Sherwood Washburn, as modern evolutionary synthesis was being formulated.

In 1950, the German-American evolutionary biologist Ernst Mayr had entered the field of anthropology, and, surveying a "bewildering diversity of names," decided to subsume human fossils into three species of Homo: "H. transvaalensis" (the australopithecines), H. erectus (including "Sinanthropus", "Pithecanthropus", and various other Asian, African, and European taxa), and H. sapiens (including anything younger than H. erectus, such as modern humans and Neanderthals), as had been broadly recommended by many prior authors. He classified Peking Man as H. e. pekinensis. Mayr defined these species as a sequential lineage, with each species evolving into the next (chronospecies). Though later Mayr changed his opinion on the australopithecines (recognising Australopithecus), his more conservative view of archaic human diversity became widely adopted in the subsequent decades. Thus, Peking Man was considered a human ancestor in both Western and Eastern thought.

"Out of Africa" theory

During the Mao era, Western scientists suspected that Chinese publications were distorted by propaganda. During the 1960s and 1970s, the position of the more ancient Australopithecus in human evolution once again became a centre of debate. In China, Wu Rukang argued that the African Australopithecus was the "missing link" between apes and humans, but was met with much derision from Chinese peers. Following the reform and opening up of China with the rise of Deng Xiaoping in 1978, Western works contradictory to tenets of Maoist ideology were circulated throughout China, radically altering Eastern anthropological discussions. In the late 20th century, human evolution had become Afrocentric with the gradual acceptance of Australopithecus as human ancestors, and the consequent marginalisation of Peking Man, especially as older fossils of H. erectus were being unearthed in Africa, first by Kenyan archaeologist Louis Leakey in 1960 with Olduvai Hominin 9. H. erectus is now largely considered to have evolved in Africa and later spread to other continents.

To counter the declining interest of Eastern palaeoanthropology in academia with the rise of Afrocentrism, many Chinese scientists commonly advanced Sinocentric and often polygenic arguments. They posited the antiquity of racial distinctness before the evolution and dispersal of modern humans, as well as the racial continuity between local H. erectus and modern descendent races; for example, they contended that "typically 'Mongoloid' features" such as shovel-shaped incisors carried over from Peking Man to modern Chinese people. They often cited the 2-million-year-old Wushan Man from central China, which is no longer classified as a human, and asserted that several Chinese apes millions of years old were human ancestors. Jia proposed that the earliest human species evolved on the Tibetan Plateau; the adjacent province of Guizhou was another popularly proposed genesis point. Various late Middle Pleistocene Chinese specimens have been argued, such as by the Chinese palaeoanthropologist Wu Xinzhi, to represent hybrid populations between Peking Man and other ancestors of modern humans, such as the Dali Man or the Jinniushan Man. In the 1970s, the travelling museum exhibit "The Exhibition of Archaeological Finds of the People's Republic of China"—organised by the Chinese Communist Party (CCP) to tour around Western Europe, the US, and Canada—painted Peking Man and Lantian Man as the "forefathers of the Chinese people", playing a central role in the story of human evolution, and emphasising the antiquity of the Chinese people. Additionally, at least since the mid-1990s, the CCP has utilised Peking Man as an instrument of its racial nationalist discourse.

Peking Man's ancestral position is still widely maintained among especially Chinese scientists using the assimilation model, wherein archaic humans such as Peking Man interbred with and were effectively absorbed into modern human populations in their respective locations. According to this model, Peking Man has lent some ancestry to modern Chinese populations. Palaeogenetic analyses—the first in 2010—have reported that all humans whose ancestry lies beyond Sub-Saharan Africa contain genes from the archaic Neanderthals and Denisovans indicating early modern humans interbred with archaic humans. The common ancestor of Neanderthals and Denisovans in turn interbred with another archaic species even further removed from modern humans. Still, East Asian H. erectus from China and Indonesia are now usually characterised as relict populations which had little interaction with Western H. erectus or later Homo species.

Phylogeny

Many Chinese H. erectus fossils were given a unique subspecies name based on minute anatomical differences. As the definition of "subspecies" tightened in the late 20th century, it became impossible to justify all of these names. In general, subspecies names for H. erectus are now used for convenience to indicate time and region rather than specific anatomical trends. The name H. e. pekinensis may extend to all Chinese H. erectus but is usually used to refer only to Zhoukoudian.

The anatomy of Chinese H. erectus specimens varies regionally and over time, but this variation is subtle and difficult to assess given how fragmentary H. erectus remains are both in and out of China. Northern Chinese specimens (namely Peking Man and Nanjing Man) are distinct in the narrowness of the skull, but H. erectus skull shape is poorly documented elsewhere in China. Some authors have suggested that the anatomical peculiarities of the Zhoukoudian specimens indicate speciation rather than a geographic cline, and consider Peking Man as a separate species, H. pekinensis.

H. erectus may have made multiple different dispersals out of Africa to the Far East, with the population represented by the Indonesian Sangiran site possibly being more closely related to Western H. erectus than to Peking Man. A population related to Peking Man may have later interbred with Southeast Asian H. erectus, since the younger teeth at Sangiran are much smaller than the older ones—more like those of Peking Man's—but tooth reduction could have happened for other reasons.

A 2026 dental proteome (tooth enamel protein) analysis identified a single amino acid polymorphism variant (a unique protein structure) in one of the Peking Man teeth preserved from the original dig (PA69). The variant, AMBN(A253G), was present in their H. erectus samples from the Hexian and Sunjiadong sites and has not been identified in any other primate, which suggests that these populations inherited it from a common ancestor. This sample also shared the AMBN(M273V) variant which has only been identified in Denisovans, and might suggest that Denisovans inherited this variant from interbreeding with local East Asian H. erectus populations like the Peking Man.

A 2021 phylogeny of H. erectus using tip dating: