View source for Solo Man

{{Short description|Extinct subspecies of Homo erectus}}
{{for|the album by Victor Willis|Solo Man (album){{!}}''Solo Man'' (album)}}
{{featured article}}
{{Subspeciesbox
| name = Solo Man
| fossil_range = [[Late Pleistocene]] {{fossilrange|0.117|0.108}}
| image = Ngandong 13 NMNH.jpg
| image_caption = Cast of Skull X at the [[Hall of Human Origins]], Washington, D.C.
| genus = Homo
| species = erectus
| subspecies = soloensis
| authority = Oppenoorth, 1932
| extinct = yes
| species_extinct = yes
| synonyms = {{species list
| Homo (Javanthropus) soloensis  | Oppenoorth, 1932
| H. sapiens soloensis  | [[Eugène Dubois|Dubois]], 1940
| H. neanderthalensis soloensis  | [[Franz Weidenreich|Weidenreich]], 1940
| Palaeoanthropus soloensis  | Evans, 1945
| H. erectus ngandongensis | Sartono, 1975
}}
| synonyms_ref = {{citation needed|date=October 2021}}
}}

'''Solo Man''' ('''''Homo erectus soloensis''''') is a [[subspecies]] of ''[[Homo erectus|H. erectus]]'' that lived along the [[Solo River]] in [[Java]], Indonesia, about 117,000 to 108,000 years ago in the [[Late Pleistocene]]. This population is the last known record of the species. It is known from 14 skullcaps, two [[tibia]]e, and a piece of the [[pelvis]] excavated near the village of Ngandong, and possibly three skulls from [[Sambungmacan crania|Sambungmacan]] and a skull from Ngawi depending on classification. The Ngandong site was first excavated from 1931 to 1933 under the direction of Willem Frederik Florus Oppenoorth, Carel ter Haar, and [[Gustav Heinrich Ralph von Koenigswald]], but further study was set back by the [[Great Depression]], [[World War II]] and the [[Indonesian War of Independence]]. In accordance with [[historical race concepts]], Indonesian ''H.&nbsp;erectus'' subspecies were originally classified as the direct ancestors of [[Aboriginal Australians]]; however, Solo Man is now thought to have no living descendants as the remains far predate modern human immigration into the area, which began roughly 55,000 to 50,000 years ago.

The Solo Man skull is oval-shaped in top view, with heavy brows, inflated cheekbones, and a prominent bar of bone wrapping around the back. The brain volume was quite large, measuring from {{convert|1013|to|1251|cm3}}, which is within the range of variation for present-day modern humans. One potentially female specimen may have been {{cvt|158|cm|ftin|0}} tall and weighed {{cvt|51|kg}}; males were probably much bigger than females. Solo Man was in many ways similar to the [[Java Man]] (''H. e. erectus'') that had earlier inhabited Java, but was far less archaic.

Solo Man likely inhabited an open [[woodland]] environment much cooler than present-day Java, along with [[elephant]]s, [[Ngandong tiger|tigers]], [[Bos palaesondaicus|wild cattle]], [[water buffalo]], [[Malayan tapir|tapirs]], and [[Hexaprotodon|hippopotamuses]], among other megafauna. They manufactured simple [[lithic flake|flakes]] and [[chopper (archaeology)|choppers]] (hand-held [[stone tool]]s), and possibly [[spear]]s or [[harpoon]]s from bones, daggers from [[stingray]] stingers, as well as [[bolas]] or [[hammerstone]]s from [[andesite]]. They may have descended from or were at least closely related to Java Man. The Ngandong specimens likely died during a volcanic eruption. The species probably went extinct with the takeover of tropical rainforest and loss of preferred habitat, beginning by 125,000 years ago. The skulls sustained damage, but it is unclear if it resulted from an assault, [[Human cannibalism|cannibalism]], the volcanic eruption, or the fossilisation process.

==Research history==
Despite what English naturalist [[Charles Darwin]] had hypothesised in his 1871 book ''[[Descent of Man]]'', many late-19th century evolutionary naturalists postulated that Asia, not Africa, was the birthplace of humankind as it is midway between Europe and America, providing optimal dispersal routes throughout the world (the [[Out of Asia theory]]). Among these was German naturalist [[Ernst Haeckel]] who argued that the first human species (which he named "''Homo primigenius''") evolved on the now-disproven hypothetical continent "[[Lemuria (continent)|Lemuria]]" in what is now Southeast Asia, 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]] (KNIL) and search for his "[[Missing link (human evolution)|missing link]]" in the [[List of islands of Indonesia|Indonesian Archipelago]]. On [[Java]], he found a skullcap and a [[femur]] ([[Java Man]]) dating to the [[late Pliocene]] or [[early Pleistocene]] at the [[Trinil]] site along the [[Solo River]], which he named [[Homo erectus|"''P.''"&nbsp;''erectus'']] (using Haeckel's hypothetical genus name) in 1893. He attempted unsuccessfully to convince the European scientific community that he had found an upright-walking ape-man. They largely dismissed his findings as a malformed non-human ape.<ref name=HsiaoPei2014>{{cite journal|first=Y.|last=Hsiao-Pei|year=2014|title=Evolutionary Asiacentrism, Peking Man, and the Origins of Sinocentric Ethno-Nationalism|journal=[[Journal of the History of Biology]]|volume=47|issue=4|pages=585–625|doi=10.1007/s10739-014-9381-4|pmid=24771020|s2cid=23308894}}</ref>{{rp|588}}

The "apeman of Java" nonetheless stirred up academic interest and, to find more remains, the [[Prussian Academy of Sciences]] in Berlin tasked German zoologist [[Emil Selenka]] with continuing the excavation of Trinil. Following his death in 1907, excavation was carried out by his wife and fellow zoologist [[Margarethe Lenore Selenka]]. Among the members was Dutch geologist Willem Frederik Florus Oppenoorth. The yearlong expedition was unfruitful, but the Geological Survey of Java continued to sponsor the excavation along the Solo River. Some two decades later, the Survey funded several expeditions to update maps of the island. Oppenoorth was made the head of the Java Mapping Program in 1930. One of their missions was to firmly distinguish [[Tertiary period|Tertiary]] and [[Quaternary]] deposits; among the relevant sites a bed [[geological dating|dating]] to the Pleistocene discovered by Dutch geologist Carel ter Haar in 1931, downriver from the Trinil site, near the village of Ngandong.<ref name=Oppenoorth1932>{{cite journal|first=W. F. F.|last=Oppenoorth|year=1932|title=Solo Man—A New Fossil Skull|journal=[[Scientific American]]|volume=147|issue=3|pages=154–155|doi=10.1038/scientificamerican0932-154|jstor=24966028|bibcode=1932SciAm.147..154O}}</ref>

{{Location map|Indonesia
|relief = yes
|width=450
|caption = Location of Ngandong on the island of [[Java]]
|alt = Ngandong is on northeast Java
|lon_deg = 111 |lon_min = 25.546 |lat_dir = S
|lat_deg = 7 |lat_min = 20.9191 |lon_dir = E
}}
From 1931 to 1933, 12 human skull pieces (including well-preserved skullcaps), as well as two right [[tibia]]e (shinbones), one of which was essentially complete, were recovered under the direction of Oppenoorth, ter Haar, and German-Dutch geologist [[Gustav Heinrich Ralph von Koenigswald]].<ref name=Huffman2010/>{{rp|2–3}} Midway through excavation, Oppenoorth retired from the Survey and returned to the Netherlands, replaced by Polish geologist {{ill|Józef Zwierzycki|pl}} in 1933. At the same time, because of the [[Great Depression]], the Survey's focus shifted to economically relevant geology, namely [[petroleum]] deposits, and the excavation of Ngandong ceased completely. In 1934, ter Haar published important summaries of the Ngandong operations before contracting [[tuberculosis]]. He returned to the Netherlands and died two years later. Von Koenigswald, who was hired principally to study Javan mammals, was fired in 1934. After much lobbying by Zwierzycki in the Survey, and after receiving funding from the [[Carnegie Institution for Science]], von Koenigswald regained his position in 1937, but was too preoccupied with the [[Sangiran]] site to continue research at Ngandong.<ref name=Huffman2010>{{cite journal|first1=O. F.|last1=Huffman|first2=J.|last2=de Vos|first3=A. W.|last3=Berkhout|first4=F.|last4=Aziz|year=2010|title=Provenience reassessment of the 1931–1933 Ngandong ''Homo erectus'' (Java), confirmation of the bone-bed origin reported by the discoverers|journal=PaleoAnthropology|volume=2010|pages=1–60|doi=10.4207/PA.2010.ART34|url=https://www.researchgate.net/publication/283591887|access-date=2021-01-13|archive-date=2021-10-04|archive-url=https://web.archive.org/web/20211004073157/https://www.researchgate.net/publication/283591887_Provenience_reassessment_of_the_1931-1933_Ngandong_Homo_erectus_Java_confirmation_of_the_bone-bed_origin_reported_by_the_discoverers|url-status=live|doi-access=free}}</ref>{{rp|23–26}}

In 1935, the Solo Man remains were transported to [[Batavia, Dutch East Indies|Batavia]] (today, [[Jakarta]], Java, Indonesia) in the care of local university professor Willem Alphonse Mijsberg, with the hope he would take over study of the specimens. Before he had the opportunity, the fossils were moved to [[Bandung]], [[West Java]] in 1942 because of the [[Japanese occupation of the Dutch East Indies]].<ref name=Huffman2010/>{{rp|23}} Japanese forces [[internment|interned]] von Koenigswald for 32 months. At the cessation of the war, he was released, but the [[Indonesian War of Independence]] erupted. Jewish-German anthropologist [[Franz Weidenreich]] (who fled China before [[Second Sino-Japanese War|the Japanese invasion]] in 1941) arranged with the [[Rockefeller Foundation]] and [[The Viking Fund]] for von Koenigswald, his wife Luitgarde, and the Javan human remains (including Solo Man) to come to New York. Von Koenigswald and Weidenreich studied the material at the [[American Museum of Natural History]]<ref>{{cite journal|last=Tobias|first=P. V.|author-link=Phillip V. Tobias|year=1976|title=The life and times of Ralph von Koenigswald: Palaeontologist extraordinary|journal=[[Journal of Human Evolution]]|volume=5|issue=5|pages=406–410|doi=10.1016/0047-2484(76)90082-8 |bibcode=1976JHumE...5..403T }}</ref> until Weidenreich's death in 1948 (leaving behind a monograph on Solo Man posthumously published in 1951).<ref name=Weidenreich1951/> In his 1956 book ''Meeting Prehistoric Men'', von Koenigswald included a 14-page account of the Ngandong project with several unpublished results. The Solo Man remains came to be stored at [[Utrecht University]], the Netherlands. In 1967, von Koenigswald gave the material to [[Teuku Jacob]] for his doctoral research. Jacob oversaw the excavation of Ngandong from 1976 to 1978 and recovered two more skull specimens and a [[pelvis|pelvic]] fragment. In 1978, von Koenigswald returned the material to Indonesia, and the Solo Man remains were moved to the [[Gadjah Mada University]], [[Special Region of Yogyakarta]] (south-central Java).<ref name=Huffman2010/>{{rp|26}}

{{multiple image|perrow=4|total_width=550px
|image1=Solo Skull I.png|caption1=Skull I
|image2=Solo Skulls I and II.png|caption2=Skulls I and II
|image3=Solo Skulls III and IV.png|caption3=Skulls III and IV
|image4=Solo Skull V.png|caption4=Skull V
|image5=Solo Skull VI.png|caption5=Skull VI
|image6=Solo Skulls VII and VIII.png|caption6=Skulls VII and VIII
|image7=Solo Skull IX.png|caption7=Skull IX
|image8=Solo Skulls IX and X.png|caption8=Skulls IX and X
|image9=Solo Skulls XI.png|caption9=Skull XI
|image10=Gorilla, Solo Man, human endocasts.png|caption10=[[Gorilla]], Solo, and modern [[endocast]]s
|image11=Solo Tibia B.png|caption11=Tibia B
|image12=Solo Tibiae A and B.png|caption12=Tibiae A (right) and B (left)
}}
The specimens are:<ref name=Weidenreich1951>{{cite journal|first1=F.|last1=Weidenreich|author1-link=Franz Weidenreich|first2=G. H. R.|last2=von Koenigswald|author2-link=Gustav Heinrich Ralph von Koenigswald|year=1951|title=Morphology of Solo man|journal=Anthropological Papers of the AMNH|volume=43|hdl=2246/297|url=https://digitallibrary.amnh.org/handle/2246/297|access-date=2021-04-04|archive-date=2021-03-30|archive-url=https://web.archive.org/web/20210330122835/http://digitallibrary.amnh.org/handle/2246/297|url-status=live}}</ref>{{rp|217}}
* Skull I, an almost complete skullcap probably belonging to an elderly female;
* Skull II, a [[frontal bone]] probably belonging to a three to seven-year-old child;
* Skull III, a warped skullcap probably belonging to an elderly individual;
* Skull IV, a skullcap probably belonging to a middle-aged female;
* Skull V, a probable male skullcap—indicated by its great length of {{cvt|221|mm}};
* Skull VI, an almost complete skullcap probably belonging to an adult female;
* Skull VII, a right [[parietal bone]] fragment probably belonging to a young, possibly female, individual;
* Skull VIII, both parietal bones (separated) possibly belonging to a young male;
* Skull IX, a skullcap missing the base probably belonging to an elderly individual (the small size is consistent with a female, but the heaviness is consistent with a male);
* Skull X, a shattered skullcap probably belonging to a robust elderly female;
* Skull XI, a nearly complete skullcap;
* Tibia A, a few fragments of the shaft, measuring {{cvt|101|mm}} in diameter at the mid-shaft, probably belonging to an adult male;
* Tibia B, a nearly complete right tibia measuring {{cvt|365|mm}} in length at {{cvt|86|mm}} in diameter at the mid-shaft, probably belonging to an adult female;
* Ngandong 15, a partial skullcap;<ref name=Huffman2010/>{{rp|3}}
* Ngandong 16, a left parietal fragment;<ref name=Huffman2010/>{{rp|3}} and
* Ngandong 17, a {{cvt|4x6|cm}} left [[acetabulum]] (on the pelvis which forms part of the [[hip joint]]).<ref name=Huffman2010/>{{rp|3}}

==Age and taphonomy==
The location of these fossils in the Solo terrace at the time of discovery was poorly documented. Oppenoorth, ter Haar, and von Koenigswald were only on site for 24 days of the 27 months of operation as they needed to oversee other Tertiary sites for the Survey. They left their geological assistants — Samsi and Panudju — to oversee the dig; their records are now lost. The Survey's site map remained unpublished until 2010 (over 75 years later) and is of limited use now, so the [[taphonomy]] and geological age of Solo Man have been contentious matters.<ref name=Huffman2010/>{{rp|5}} All 14 specimens were reported to have been found in the upper section of Layer&nbsp;II (of six layers), which is a {{cvt|46|cm}}-thick [[stratum]] with gravelly sand and [[volcaniclastics|volcaniclastic]] [[hypersthene]] [[andesite]]. They are thought to have been deposited at around the same time, probably in a now-dry arm of the Solo River, about {{cvt|20|m}} above the modern river. The site is about {{cvt|40|m}} above [[sea level]].<ref name=Huffman2010/>{{rp|15–18}}
[[File:Ngandong excavation.png|thumb|upright=1.5|alt=Photograph of the excavation of a skull at Ngandong|Excavation of Skull VI at Ngandong, 1932]]

Volcaniclastic rock indicates deposition occurred soon after a [[volcanic eruption]]. Because of the sheer volume of fossils, humans and animals may have concentrated in great numbers in the valley upstream from the site due to the eruption or extreme drought. The ash would have poisoned the vegetation, or at least impeded its growth, leading to starvation and death among herbivores and humans, accumulating a mass of carcasses decomposing over several months. A lack of carnivore damage may indicate sufficient feeding was possible without having to resort to crunching through the bone. When the [[monsoon]] season came, [[lahars]] streaming from the volcano through the river channels swept the carcasses to the Ngandong site, where they and other debris created a jam because of the channel narrowing there.<ref>{{cite journal|last1=Huffman|first1=O. F.|first2=J.|last2=de Vos|first3=A.|last3=Balzeau|first4=A. W.|last4=Berkhout|first5=B.|last5=Voight|title=Mass death and lahars in the taphonomy of the Ngandong ''Homo erectus'' bonebed, and volcanism in the hominin record of eastern Java|journal=Abstracts of the PaleoAnthropology Society 2010 Meetings, PaleoAnthropology|year=2010|page=A14|url=https://www.academia.edu/1297259|access-date=2021-06-29|archive-date=2021-06-29|archive-url=https://web.archive.org/web/20210629131647/https://www.academia.edu/1297259|url-status=live}}</ref><ref name=Rizal2020/> The ''H. erectus'' fossils from [[Sambungmacan crania|Sambungmacan]], also along the Solo River, were possibly deposited in the same event.<ref name=Huffman2010/>

The dating attempts are:
* In 1932, based on the site's height above the present-day river, Oppenoorth suggested Solo Man dated to the [[Eemian]] interglacial, which at the time was roughly constrained to 150 to 100 thousand years ago from the [[Middle Pleistocene|Middle]]/[[Late Pleistocene]] transition.<ref name=Oppenoorth1932/> Later [[biochronology|biochronological]] studies (using the animal remains to constrain the age) within the next few years by Oppenoorth in 1932, von Koenigswald in 1934, and ter Haar in 1936 agreed with a Late Pleistocene date.<ref name=Swisher1996/>
* The Solo Man remains were first [[radiometrically dated]] in 1988 and again in 1989, using [[uranium–thorium dating]], to 200 to 30 thousand years ago, a wide error range.<ref name=Yokoyama2008/>
* In 1996, Solo Man teeth were dated, using [[electron spin resonance dating]] (ESR) and uranium–thorium [[isotope-ratio mass spectrometry]], to 53.3 to 27 thousand years ago; this would mean Solo Man outlasted continental ''H.&nbsp;erectus'' by at minimum 250,000 years and was contemporaneous with modern humans in Southeast Asia,<ref name=Swisher1996>{{cite journal|first1=C. C.|last1=Swisher, III|first2=W. J.|last2=Rink|first3=S. C.|last3=Antón|last4=Schwarcz|first4=H. P.|last5=Curtis|first5=G. H.|last6=Widiasmoro|first6=A. S.|year=1996|title=Latest ''Homo erectus'' of Java: Potential Contemporaneity with Homo sapiens in Southeast Asia|journal=[[Science (journal)|Science]]|volume=274|issue=5294|pages=1870–1874|doi=10.1126/science.274.5294.1870|jstor=2891688|pmid=8943192|bibcode=1996Sci...274.1870S|s2cid=22452375}}</ref> who immigrated roughly 55 to 50 thousand years ago.<ref>{{cite journal|first1=J. F.|last1=O'Connell|first2=J.|last2=Allen|first3=M. A. J.|last3=Williams|first4=A. N.|last4=Williams|first5=C. S. M.|last5=Turney|first6=N. A.|last6=Spooner|first7=J.|last7=Kamminga|first8=G.|last8=Brown|first9=A.|last9=Cooper|year=2018|title=When did ''Homo sapiens'' first reach Southeast Asia and Sahul?|journal=[[Proceedings of the National Academy of Sciences of the United States of America|Proceedings of the National Academy of Sciences]]|volume=115|issue=34|pages=8482–8490|doi=10.1073/pnas.1808385115|pmid=30082377|pmc=6112744|bibcode=2018PNAS..115.8482O |doi-access=free}}</ref>
* In 2008, [[gamma spectroscopy]] on three of the skulls showed they experienced uranium leaching, and the Solo Man remains were re-dated to roughly 70 to 40 thousand years ago. This would still make it possible Solo Man was contemporaneous with modern humans.<ref name=Yokoyama2008>{{cite journal|first1=Y.|last1=Yokoyama|first2=C.|last2=Falguères|first3=F.|last3=Sémah|first4=T.|last4=Jacob|author4-link=Teuku Jacob|year=2008|title=Gamma-ray spectrometric dating of late ''Homo erectus'' skulls from Ngandong and Sambungmacan, Central Java, Indonesia|journal=[[Journal of Human Evolution]]|volume=55|issue=2|pages=274–277|doi=10.1016/j.jhevol.2008.01.006|pmid=18479734 |bibcode=2008JHumE..55..274Y }}</ref>
* In 2011, [[argon–argon dating]] of [[pumice]] [[hornblende]] yielded a maximum age of 546 ± 12 thousand years ago, and ESR and uranium–thorium dating of a mammal bone just downstream at the Jigar&nbsp;I site a minimum age of 143 to 77 thousand years ago. This extended interval would make it possible Solo Man was contemporaneous with continental ''H.&nbsp;erectus'', long before modern humans dispersed across the continent.<ref>{{cite journal|first1=E.|last1=Indriati|first2=C. C.|last2=Swisher III|first3=C.|last3=Lepre|first4=R. L.|last4=Quinn|first5=R. A.|last5=Suriyanto|first6=A. T.|last6=Hascaryo|first7=R.|last7=Grün|first8=C. S.|last8=Feibel|first9=B. L.|last9=Pobiner|first10=M.|last10=Aubert|first11=W.|last11=Lees|first12=S. C.|last12=Antón|year=2011|title=The Age of the 20 Meter Solo River Terrace, Java, Indonesia and the Survival of ''Homo erectus'' in Asia|journal=[[PLOS One]]|volume=6|issue=6|article-number=e21562|doi=10.1371/journal.pone.0021562|pmc=3126814|pmid=21738710|bibcode=2011PLoSO...621562I|doi-access=free}}</ref>
* In 2020, the first comprehensive chronology of the Ngandong site was published which found the Solo River was diverted through the site 500,000 years ago; the Solo terrace was deposited over 316 to 31 thousand years ago; the Ngandong terrace 141 to 92 thousand years ago; and the ''H.&nbsp;erectus'' bone bed 117 to 108 thousand years ago. This would mean Solo Man is indeed the last known ''H.&nbsp;erectus'' population and did not interact with modern humans.<ref name=Rizal2020>{{Cite journal|last1=Rizal|first1=Y.|last2=Westaway|first2=K. E.|last3=Zaim|first3=Y.|last4=van den Bergh|first5=E. A.|last5=Bettis III|first6=M. J.|last6=Morwood|first7=O. F. |last7=Huffman|first8=R.|last8=Grün|first9=R.|last9=Joannes-Boyau|first10=R. M.|last10=Bailey|author11=Sidarto|first12=M. C.|last12=Westaway|first13=I.|last13=Kurniawan|first14=M. W.|last14=Moore|first15=M.|last15=Storey|first16=F.|last16=Aziz|author17=Suminto|first18=J.|last18=Zhao|author19=Aswan|first20=M. E.|last20=Sipola|first21=R.|last21=Larick|first22=J.-P.|last22=Zonneveld|first23=R.|last23=Scott|first24=S.|last24=Putt|first25=R. L.|last25=Ciochon|year=2020|title=Last appearance of ''Homo erectus'' at Ngandong, Java, 117,000–108,000 years ago|journal=[[Nature (journal)|Nature]]|volume=577|issue=7790|pages=381–385|doi=10.1038/s41586-019-1863-2|issn=0028-0836|pmid=31853068|s2cid=209410644|hdl=10072/397335|hdl-access=free}}</ref>

==Classification==
===Raciology===
[[File:Report_on_the_human_crania_and_other_bones_of_the_skeletons_collected_during_the_voyage_of_H._M._S._Challenger_in_the_years_1873-1876.png|thumb|left|alt= Photograph of three skulls in front and side view, used by Sir William Turner to racially define Aboriginal Australians|Three skulls [[William Turner (anatomist)|Sir William Turner]] used to racially define [[Aboriginal Australians]] in 1884 (Solo Man was later classified as ancestral to this population<ref name=Curnoe2010/>)]]
The racial classification of [[Aboriginal Australians]], because of the robustness of the skull compared to that of other modern-day populations, has historically been a complicated question for European science since [[Johann Friedrich Blumenbach]] (the founder of [[physical anthropology]]) introduced the topic in 1795 in his ''De Generis Humani Varietate Nativa'' ("On the Natural History of Mankind"). Following the conception of [[evolution]] by Darwin, English anthropologist [[Thomas Henry Huxley]] suggested an ancestor–descendant relationship between European [[Neanderthal]]s and Aboriginal Australians in 1863, which was furthered by later racial anthropologists until the discovery of Indonesian archaic humans.<ref name=Curnoe2010/>

In 1932, Oppenoorth preliminarily drew parallels between the Solo Man skull and that of [[Rhodesian Man]] from Africa, Neanderthals, and modern day Aboriginal Australians.<ref name=Oppenoorth1932/> At the time, humans were generally believed to have originated in Central Asia, as championed primarily by American palaeontologist [[Henry Fairfield Osborn]] and his protégé [[William Diller Matthew]]. They believed Asia was the "mother of continents" and the rising of the [[Himalayas]] and [[Tibet]] and subsequent drying of the region forced human ancestors to become terrestrial and [[bipedal]]. They maintained that populations which retreated to the tropics – namely Dubois's Java Man and the "[[Negroid race]]" — substantially regressed ([[degeneration theory]]). They also rejected [[Raymond Dart]]'s South African [[Taung child]] (''[[Australopithecus africanus]]'') as a human ancestor, favouring the hoax [[Piltdown Man]] from Britain.<ref name=HsiaoPei2014/>{{rp|599–602}} At first, Oppenoorth believed the Ngandong material represented an Asian type of Neanderthal which was more closely allied with the Rhodesian Man (also considered a Neanderthal type), and gave it a generic distinction as "''Javanthropus soloensis''". Dubois considered Solo Man to be more or less identical to the East Javan [[Wajak crania|Wajak Man]] (now classified as a modern human), so Oppenoorth subsequently began using the name "''Homo (Javanthropus) soloensis''".<ref name=Weidenreich1951/> Oppenoorth hypothesised that the Java Man evolved in Indonesia and was the predecessor of modern day Aboriginal Australians, Solo Man being a [[transitional fossil]]. He considered Rhodesian Man a member of this same group. As for the Chinese [[Peking Man]] (now ''H. e. pekinensis''), he believed it dispersed west and gave rise to the Neanderthals.<ref name=Oppenoorth1932/>

Thus, the ancient Java Man, Solo Man, and Rhodesian Man were commonly grouped together in the "Pithecanthropoid-[[Australoid]]" lineage. "Australoid" includes Aboriginal Australians and [[Melanesians]]. This was an extension of the [[multiregional origin of modern humans]] championed by Weidenreich and American racial anthropologist [[Carleton S. Coon]], who believed that all modern [[race (human categorization)|races]] and ethnicities (which were classified into separate subspecies or even species until the mid-20th century) evolved independently from a local archaic human species ([[polygenism]]). Aboriginal Australians were considered the most primitive race alive.<ref name=Curnoe2010/> In the 1950s, German evolutionary biologist [[Ernst Mayr]] entered the field of palaeoanthropology, and, surveying a "bewildering diversity of names", decided to define only three species of ''Homo'': "''H. transvaalensis''" (the [[australopithecines]]), ''H. erectus'' (including Solo Man and several putative African and Asian taxa), and ''Homo sapiens'' (including anything younger than ''H. erectus'', such as modern humans and Neanderthals). Mayr defined them as a sequential lineage, each species evolving into the next ([[chronospecies]]). Though Mayr later changed his opinion on the australopithecines (recognising ''[[Australopithecus]]''), and a few species have since been named or regained some acceptance, his more conservative view of [[archaic human]] diversity became widely adopted in the subsequent decades.<ref name=Schwartz2010>{{cite journal|last1=Schwartz|first1=J. H.|author1-link=Jeffrey H. Schwartz|last2=Tattersall|first2=I.|author2-link=Ian Tattersall|year=2010|title=Fossil evidence for the origin of ''Homo sapiens''|journal=[[American Journal of Physical Anthropology]]|volume=143|issue=S51|pages=96–98; 101–103|doi=10.1002/ajpa.21443|pmid=21086529|bibcode=2010AJPA..143S..94S |doi-access=free}}</ref>

Though Mayr did not expand upon the subspecies of ''H. erectus'', subsequent authors began formally sinking species from all parts of the Old World into it. Solo Man was placed into the "Neanderthal/Neanderthalien/Neanderthaloid group" by Weidenreich in the 1940s, which he reserved for specimens apparently transitional between ''H. erectus'' and ''H. sapiens''. The group could also be classified under the now-defunct genus "''Palaeoanthropus''". Solo man was first classified as a subspecies of ''H. erectus'' by Coon in his 1962 book ''The Origin of Races''.<ref>{{cite book|first=W. W.|last=Howells|year=1981|chapter=5. ''Homo erectus'' in human descent: ideas and problems|title=Homo erectus: Papers in Honor of Davidson Black|publisher=University of Toronto Press|page=68|jstor=10.3138/j.ctvcj2jdw.11|isbn=978-1-4875-8537-2}}</ref>

===Assimilation===
[[File:Willandra Lakes Human 50 calvaria.png|thumb|alt=Photograph of the WLH-50 skullcap |The [[WLH-50]] skullcap, one of the oldest modern human remains of Australia, was used as evidence of Solo Man/modern human interbreeding.<ref name=Curnoe2010/>]]
The claim that Aboriginal Australians were descended from Asian ''H. erectus'' was expanded upon in the 1960s and 1970s as some of the oldest known (modern) human fossils were being recovered from Australia, primarily under the direction of Australian anthropologist [[Alan Thorne]]. He noted some populations were prominently more robust than others, so he suggested Australia was colonised in two waves ("di-hybrid model"): the first wave being highly robust and descending from nearby ''H. erectus'', and the second wave more gracile (less robust) and descending from anatomically modern East Asians (who, in turn, descended from Chinese ''H.&nbsp;erectus''). It was subsequently discovered that some of the more robust specimens are geologically younger than the gracile ones.<ref name=Curnoe2010/>{{rp|3}}

By the 1980s, as African species like ''A.&nbsp;africanus'' became widely accepted as human ancestors and race became less salient in anthropology, the [[recent African origin of modern humans|Out of Africa]] theory overturned the Out of Asia and multiregional models. The multiregional model was consequently reworked into local populations of archaic humans having interbred and contributed at least some ancestry to modern populations in their respective regions, otherwise known as the assimilation model. Solo Man fits into this by having hybridised with the fully modern ancestors of Aboriginal Australians travelling south through Southeast Asia. The assimilation model was not ubiquitously supported.<ref name=Curnoe2010/>{{rp|3}}

In 2006, Australian palaeoanthropologist Steve Webb speculated instead that Solo Man was the first human species to reach Australia, and more robust modern Australian specimens represent hybrid populations.<ref name=Curnoe2010>{{cite journal|first=D.|last=Curnoe|year=2011|title=A 150-Year Conundrum: Cranial Robusticity and Its Bearing on the Origin of Aboriginal Australians|journal=International Journal of Evolutionary Biology|volume=2011|pages=2–3|doi=10.4061/2011/632484|pmid=21350636|pmc=3039414|doi-access=free}}</ref>{{rp|3}}

===Present===
The date of 117 to 108 thousand years ago for Solo Man, predating modern human dispersal through Southeast Asia (and eventually into Australia), is at odds with this conclusion. Such an ancient date leaves Solo Man with no living descendants.<ref name=Rizal2020/> Similarly, a 2021 genomic study looking at the genomes of over 400 modern humans (of which 200 came from [[Maritime Southeast Asia|Island Southeast Asia]]) found no evidence of any "super-archaic" (i. e. ''H.&nbsp;erectus'') [[interbreeding between archaic and modern humans|interbreeding]].<ref name=Teixeira2021>{{cite journal|first1=J. C.|last1=Teixeira|first2=G. S.|last2=Jacobs|first3=C.|last3=Stringer|author3-link=Chris Stringer|first4=J.|last4=Tuke|first5=G.|last5=Hudjashov|first6=G. A.|last6=Purnomo|first7=H.|last7=Sudoyo|first8=M. P.|last8=Cox|first9=R.|last9=Tobler|first10=C. S. M.|last10=Turney|first11=A.|last11=Cooper|first12=K. M.|last12=Helgen|year=2021|title=Widespread Denisovan ancestry in Island Southeast Asia but no evidence of substantial super-archaic hominin admixture|journal=[[Nature Ecology and Evolution]]|volume=5|issue=5|pages=616–624|doi=10.1038/s41559-021-01408-0|pmid=33753899|bibcode=2021NatEE...5..616T |s2cid=232323599|url=https://www.repository.cam.ac.uk/handle/1810/321355}}</ref>

Solo Man has generally been considered to have descended from Java Man (''H.&nbsp;e.&nbsp;erectus'', typified by the Sangiran/Trinil populations), and the three skulls from Sambungmacan and the skull from Ngawi have been assigned to ''H.&nbsp;e.&nbsp;soloensis'' or some intermediary stage between ''H.&nbsp;e.&nbsp;erectus'' and ''H.&nbsp;e.&nbsp;soloensis''. It is largely unclear if there was gene flow from the continent. The alternate hypothesis, first proposed by Jacob in 1973, is that the Sangiran/Trinil and Ngandong/Ngawi/Sambungmacan populations were [[sister taxon|sister groups]] that evolved [[parallel evolution|parallel]] to each other.<ref name=Kaifu2008>{{cite journal|last1=Kaifu|first1=Y.|last2=Aziz|first2=F.|first3=E.|last3=Indriati|first4=T.|last4=Jacob|first5=I.|last5=Kurniawan|first6=H.|last6=Baba|year=2008|title=Cranial morphology of Javanese ''Homo erectus'': New evidence for continuous evolution, specialization, and terminal extinction|journal=[[Journal of Human Evolution]]|volume=55|issue=4|page=578|doi=10.1016/j.jhevol.2008.05.002|pmid=18635247 |bibcode=2008JHumE..55..551K }}</ref> If the alternate is correct, this could warrant species distinction as "''H.&nbsp;soloensis''", but the definitions of species and subspecies, especially in [[palaeoanthropology]], are poorly drawn.<ref>{{cite journal|first1=V.|last1=Zeitoun|first2=F.|last2=Détroit|first3=D.|last3=Grimaud-Hervé|first4=H.|last4=Widianto|year=2010|title=Solo man in question: Convergent views to split Indonesian ''Homo erectus'' in two categories|journal=[[Quaternary International]]|volume=223–224|page=288|doi=10.1016/j.quaint.2010.01.018|bibcode=2010QuInt.223..281Z|s2cid=84764668 |url=https://hal.archives-ouvertes.fr/hal-02977578/file/Solo.pdf|access-date=2021-05-22|archive-date=2021-04-29|archive-url=https://web.archive.org/web/20210429071324/https://hal.archives-ouvertes.fr/hal-02977578/file/Solo.pdf|url-status=live}}</ref>

==Anatomy==
[[File:Solo Man reconstruction.png|thumb|Speculative reconstruction of a complete skull by [[Franz Weidenreich]]]]
The identification as adult or juvenile was based on the closure of the cranial [[suture (anatomy)|sutures]], assuming they closed at a rate similar to modern humans (though they may have closed at earlier ages in ''H.&nbsp;erectus''). Characteristic of ''H.&nbsp;erectus'', the skull is exceedingly thick in Solo Man, ranging from double to triple what would be seen in modern humans. Male and female specimens were distinguished by assuming males were more robust than females, though both males and females are exceptionally robust compared to other Asian ''H.&nbsp;erectus''. The adult skulls average {{cvt|202x152|mm}} in length times breadth, and are proportionally similar to that of the Peking Man but have a much larger circumference. Skull V is the longest at {{cvt|221|mm}}.<ref name=Weidenreich1951/>{{rp|236–239}} For comparison, the dimensions of modern human skulls average {{cvt|176x145|mm}} for men and {{cvt|171x140|mm}} for women.<ref>{{cite journal|first1=H.|last1=Li|first2=J.|last2=Ruan|first3=Z.|last3=Xie|first4=H.|last4=Wang|first5=W.|last5=Liu|year=2007|title=Investigation of the critical geometric characteristics of living human skulls utilising medical image analysis techniques|journal=International Journal of Vehicle Safety|volume=2|issue=4|page=345|doi=10.1504/IJVS.2007.016747}}</ref>

The Solo Man remains are characterised by more [[synapomorphy and apomorphy|derived]] traits than more archaic Javan ''H.&nbsp;erectus'', most notably a larger brain size, an elevated [[cranial vault]], reduced [[postorbital constriction]], and less developed brow ridges. They still closely resemble earlier ''H.&nbsp;erectus''.<ref name=Kaifu2008/> Like Peking Man, there was a slight [[sagittal keel]] running across the midline of the skull. Compared to other Asian ''H.&nbsp;erectus'', the forehead is proportionally low and also has a low angle of inclination. The brow ridges do not form a continuous bar like in Peking Man, but curve downwards at the midpoint, forming a nasal bridge. The brows are quite thick, especially at the lateral ends (nearest the edge of the face). Like Peking Man, the [[frontal sinus]]es are confined to between the eyes rather than extending into the brow region. Compared to Neanderthals and modern humans, the area the [[temporal muscle]] would have covered is rather flat. The brow ridges merge into markedly thickened cheek bones. The skull is phenozygous, in that the skullcap is proportionally narrow compared to the cheekbones, so that the latter are still visible when looking down at the skull in top-view. The [[squamous part of the temporal bone]] is triangular like that of Peking Man, and the [[infratemporal crest]] is quite sharp.<ref name=Weidenreich1951/>{{rp|240–242}} Like earlier Javan ''H.&nbsp;erectus'', the inferior and superior [[parietal bone|temporal lines]] (on the parietal bone) diverge towards the back of the skull.<ref name=Anton2003/>{{rp|143}}

At the back of the skull, there is a sharp, thick occipital torus (a projecting bar of bone) which marks a clear separation between the [[squamous part of occipital bone|occipital and nuchal planes]]. The occipital torus projects the most at the part corresponding to the [[external occipital protuberance]] in modern humans. The base of the temporal bone is consistent with Java Man and Peking Man rather than Neanderthals and modern humans. Unlike Neanderthals and modern humans, there is a defined bony pyramid structure near the root of the [[pterygoid bone]]. The [[mastoid part of the temporal bone]] at the base of the skull notably juts out. The [[occipital condyles]] (which connect the skull to the [[vertebral column|spine]]) are proportionally small compared to the [[foramen magnum]] (where the [[spinal cord]] passes into the skull). Large, irregular bony projections lie directly behind the occipital condyles.<ref name=Weidenreich1951/>{{rp|246–249}}

The brain volumes of the six Ngandong specimens for which the metric is calculable range from {{cvt|1,013|to|1,251|cc}}. The Ngawi&nbsp;I skull measures {{cvt|1,000|cc}}; and the three Sambungmacan skulls {{cvt|1,035|,|917|and|1,006|cc}}. This makes for an average of over {{cvt|1,000|cc}}.<ref name=Anton2003>{{cite journal|first=S. C.|last=Antón|year=2003|title= Natural history of ''Homo erectus''†|journal=[[American Journal of Physical Anthropology]]|volume=122|issue=37|pages=136–152|doi=10.1002/ajpa.10399|pmid=14666536|bibcode=2003AJPA..122S.126A |doi-access=free}}</ref>{{rp|136}} Overall, Asian ''H.&nbsp;erectus'' are big-brained, averaging roughly {{cvt|1,000|cc}}.<ref name=Anton2016>{{cite journal|first1=S. C.|last1=Antón|first2=H. G.|last2=Taboada|first3=E. R.|last3=Middleton|first4=C. W.|last4=Rainwater|first5=A. B.|last5=Taylor|first6=T. R.|last6=Turner|first7=J. E.|last7=Turnquist|first8=K. J.|last8=Weinstein|first9=S. A.|last9=Williams|year=2016|title=Morphological variation in ''Homo erectus'' and the origins of developmental plasticity|journal=[[Philosophical Transactions of the Royal Society B]]|volume=371|issue=1698|article-number=20150236|doi=10.1098/rstb.2015.0236|pmc=4920293|pmid=27298467}}</ref> For comparison, a 1955 survey of 63 Aboriginal Australians reported a brain volume range of {{cvt|943|to|1399|cc}}; that is, Asian ''H. erectus'' brain volume fits within the modern human range of variation.<ref>{{Cite journal|doi = 10.2478/anre-2021-0029|title = Interpopulational variation in human brain size: Implications for hominin cognitive phylogeny|year = 2022|last1 = Clark|first1 = G.|last2 = Henneberg|first2 = M.|journal = Anthropological Review|volume = 84|issue = 4|pages = 405–429|doi-access = free}}</ref>  The base of the braincase, and thus the brain, seems to have been flat rather than curved. The [[sella turcica]] at the base of the skull, near the [[pituitary gland]], is much larger than that of modern humans, which Weidenreich in 1951 cautiously attributed to an enlarged gland which caused the extraordinary thickening of the bones.<ref name=Weidenreich1951/>{{rp|285}}

Of the two known tibiae, Tibia&nbsp;A is much more robust than Tibia&nbsp;B and is consistent overall with Neanderthal tibiae.<ref name=Weidenreich1951/> Like other ''H.&nbsp;erectus'', the tibiae are thick and heavy. Based on the reconstructed length of {{cvt|380|mm}}, Tibia&nbsp;B may have belonged to a {{cvt|158|cm|ftin|0}} tall, {{cvt|51|kg}} individual. Tibia&nbsp;A is assumed to have belonged to a larger individual. Asian ''H.&nbsp;erectus'', for which height estimates are taken (a rather small sample size), typically range from {{cvt|150–160|cm|ftin|0}}, with Indonesian ''H.&nbsp;erectus'' in tropical environments typically scoring on the higher end, and continental specimens in colder latitudes on the lower end. The single pelvic fragment from Ngandong has not yet been described formally.<ref name=Anton2003/>{{rp|151–152}}

{{Multiple image|align=center|total_width=1150px|image1=Solo Skull XI anterior.png|image2=Solo Skull XI posterior.png|image3=Solo Skull XI lateral.png|image4=Solo Skull XI dorsal.png|image5=Solo Skull VI ventral.png|footer=Views and notes of (from left to right) Skull XI from the front, back, left side, and top, and Skull VI from the underside, [[Franz Weidenreich]], 1951}}

==Culture==
===Palaeohabitat===
At the species level, the Ngandong fauna is similar overall to the older Kedung Brubus fauna roughly 800 to 700 thousand years ago, a time of mass immigration of large mammal species to Java, including [[Elephas|Asian elephants]] and ''[[Stegodon]]''. Other Ngandong fauna include the tiger ''[[Panthera tigris soloensis]]'', [[Malayan tapir]], the hippo ''[[Hexaprotodon]]'', [[Rusa (genus)|sambar deer]], [[water buffalo]], the cow ''[[Bos palaesondaicus]]'', [[Sus (genus)|pigs]], and [[crab-eating macaque]]. These are consistent with an open [[woodland]] environment.<ref name=bergh2001/> The presence of the [[common crane]] in the nearby contemporaneous Watualang site could indicate much cooler conditions than today.<ref name=Bellwood1997/> The driest conditions probably corresponded to the glacial maximum roughly 135,000 years ago, exposing the [[Sunda shelf]] and connecting the major Indonesian islands to the continent. By 125,000 years ago, the climate became much wetter, making Java an island, and allowing for the expansion of tropical rainforests. This caused the succession of the Ngandong fauna by the Punung fauna, which represents the modern day animal assemblage of Java, though more typical Punung fauna — namely [[orangutans]] and [[gibbon]]s — probably could not penetrate the island until it was reconnected to the continent after 80,000 years ago.<ref name=bergh2001>{{cite journal|last1=Van den Bergh|first1=G. D.|last2=de Vos|first2=J.|last3=Sondaar|first3=P. Y.|year=2001|title=The Late Quaternary palaeogeography of mammal evolution in the Indonesian Archipelago|journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]]|volume=171|issue=3–4|pages=387–392|doi=10.1016/s0031-0182(01)00255-3|bibcode=2001PPP...171..385V}}</ref> ''H. erectus'', a specialist in woodland and savannah biomes, likely went extinct with the loss of the last open-habitat refugia.<ref>{{cite journal|first1=J.|last1=Louys|first2=P.|last2=Roberts|year=2020|title=Environmental drivers of megafauna and hominin extinction in Southeast Asia|journal=[[Nature (journal)|Nature]]|volume=586|issue=7829|pages=402–406|doi=10.1038/s41586-020-2810-y|pmid=33029012|bibcode=2020Natur.586..402L|hdl=10072/402368|s2cid=222217295|hdl-access=free}}</ref>

''H.&nbsp;e.&nbsp;soloensis'' was the last population of a long occupation history of the island of Java by ''H.&nbsp;erectus'', beginning 1.51 to 0.93 million years ago at the Sangiran site, continuing 540 to 430 thousand years ago at the Trinil site, and finally 117 to 108 thousand years ago at Ngandong. If the date is correct for Solo Man, then they would represent a terminal population of ''H.&nbsp;erectus'' which sheltered in the last open-habitat refuges of East Asia before the rainforest takeover. Before the immigration of modern humans, Late Pleistocene Southeast Asia was also home to ''[[Homo floresiensis|H.&nbsp;floresiensis]]'' endemic to the island of [[Flores]], Indonesia, and ''[[Homo luzonensis|H.&nbsp;luzonensis]]'' endemic to the island of [[Luzon]], the Philippines. Genetic analysis of present-day Southeast Asian populations indicates the widespread dispersal of the [[Denisovans]] (a species currently recognisable only by their genetic signature) across Southeast Asia, whereupon they interbred with immigrating modern humans 45.7 and 29.8 thousand years ago.<ref name=Rizal2020/> A 2021 genomic study indicates that, aside from the Denisovans, modern humans never interbred with any of these endemic human species, unless the offspring were [[hybrid incompatibility|unviable]] or the hybrid lineages have since died out.<ref name=Teixeira2021/>

Judging by the sheer number of specimens deposited at Ngandong at the same time, there may have been a sizeable population of ''H.&nbsp;e&nbsp;soloensis'' before the volcanic eruption which resulted in their interment, but population is difficult to approximate with certainty. The Ngandong site was some distance away from the northern coast of the island, but it is unclear where the southern shoreline and the mouth of the Solo River would have been.<ref name=Huffman2010/>

===Technology===
[[File:Solo Valley tools.png|thumb|left|alt=Sketches of supposed Solo Man tools including a stingray barb, a bone harpoon or spearhead and a deer antler fragment|Supposed Solo Man tools: a) [[stingray]] barb, b) bone [[harpoon]] or spearhead, c) deer [[antler]] fragment]]
In 1936, while studying photos taken by Dutch archaeologist {{ill|Pieter Vincent van Stein Callenfels|nl}}, Oppenoorth made note of several broken animal bone remains, most notably damage to a large tiger skull and some deer [[antlers]], which he considered evidence of [[bone tool|bone technology]]. He suggested some deer antlers had a carved bird skull [[hafting|hafted]] onto the end to be used as axes. In 1951, Weidenreich voiced his scepticism—as the bones were invariably damaged by the river, and perhaps [[crocodiles]] and other natural processes—arguing instead that none of the bones reliably show any evidence of human modification. Oppenoorth further suggested a long piece of bone carved with an undulating pattern on both sides was used as a [[harpoon]], similar to harpoons manufactured in the [[Magdalenian]] of Europe, but Weidenreich interpreted it as a spearhead. Weidenreich made note of anomalous inland [[stingray]] stingers at Ngandong, which he supposed were collected by Solo Man for use as daggers or arrowheads, similar to some recent South Pacific peoples.<ref name=Weidenreich1951/>{{rp|216–218}} It is unclear if this apparent bone technology can be associated with Solo Man or later modern human activity,<ref name=Bellwood1997>{{cite book|first=P.|last=Bellwood|year=1997|chapter=''Homo erectus'' in Sundaland|title=Prehistory of the Indo-Malaysian Archipelago: Revised Edition|location=Honolulu|publisher=[[University of Hawaii Press]]|pages=65–66|jstor=j.ctt24hf81.5|isbn=978-1-921313-11-0}}</ref> though the Trinil ''H.&nbsp;e.&nbsp;erectus'' population seems to have worked with such material, manufacturing [[scraper (archaeology)|scrapers]] from ''[[Pseudodon shell DUB1006-fL|Pseudodon]]'' shells and possibly opening them up with [[shark tooth|shark teeth]].<ref>{{cite journal | last1 = Joordens | first1 = J. C. A. |first2=F.|last2=d'Errico|first3=F. P.|last3=Wesselingh|first4=S.|last4=Munro|first5=J.|last5=de Vos|first6=J.|last6=Wallinga|first7=C.|last7=Ankjærgaard|first8=T.|last8=Reimann|first9=J. R.|last9=Wijbrans|first10=K. F.|last10=Kuiper|first11=H. J.|last11=Mücher|first12=H.|last12=Coqueugniot|first13=V.|last13=Prié|first14=I.|last14=Joosten|first15=B.|last15=van Os|first16=A. S.|last16=Schulp|first17=M.|last17=Panuel|first18=V.|last18=van der Haas|first19=W.|last19=Lustenhouwer|first20=J. J. G.|last20=Reijmer|first21=W.|last21=Roebroeks | year = 2015| title = ''Homo erectus'' at Trinil on Java used shells for tool production and engraving | journal = Nature | volume = 518 | issue = 7538| pages = 228–231 | doi = 10.1038/nature13962 | pmid = 25470048 | bibcode = 2015Natur.518..228J | s2cid = 4461751 }}</ref>

Oppenoorth also identified a perfectly round andesite stone ball from Ngandong, a common occurrence in the Solo Valley, ranging in diameter from {{cvt|67|to|92|mm}}. As well, similar balls have been identified in contemporaneous and younger European [[Mousterian]] and African [[Middle Stone Age]] sites, as ancient as African [[Acheulean]] sites (notably [[Olorgesailie]], Kenya).<ref name=Weidenreich1951/> On Java, they have been found at Watualang (contemporaneous with Ngandong) and Sangiran.<ref name=Semah2014>{{cite book|first1=F.|last1=Semáh|first2=T.|last2=Simanjuntak|first3=E.|last3=Dizon|first4=C.|last4=Gaillard|first5=A.-M.|last5=Semáh|year=2014|chapter=Insular Southeast Asia in the Lower Paleolithic|title=Encyclopedia of Global Archaeology|editor-first=C.|editor-last=Smith|publisher=[[Springer Science+Business Media]]|pages=3909, 3914|doi=10.1007/978-1-4419-0465-2_1907|isbn=978-1-4419-0466-9|s2cid=239106990 }}</ref> Traditionally, these have been interpreted as [[bolas]] (tied together in twos or threes and flung as a hunting weapon), but also individually thrown projectiles, club heads, or plant-processing or bone-breaking tools. In 1993, American archaeologists [[Kathy Schick]] and [[Nicholas Toth]] demonstrated the spherical shape could be reproduced simply if the stone is used as a [[hammerstone|hammer]] for an extended period.<ref>{{cite book|first1=K. D.|last1=Schick|author1-link=Kathy Schick|first2=N. P.|last2=Toth|author2-link=Nicholas Toth|year=1994|chapter=Fashioning our future: the making of early stone tools|title=Making silent stones speak: human evolution and the dawn of technology|publisher=[[Simon and Schuster]]|pages=132–133|isbn=978-0-671-87538-1}}</ref>

In 1938, von Koenigswald returned to the Ngandong site along with archaeologists [[Helmut de Terra]], [[Hallam L. Movius]] and [[Pierre Teilhard de Chardin]] to collect [[lithic cores]] and [[lithic flake|flakes]] (i.e. [[stone tools]]). Because of wear caused by the river, it is difficult to identify with confidence that some of these rocks are actual tools. They are small and simple, usually smaller than {{cvt|5|cm|0}} and made most commonly of [[chalcedony]] (but also [[chert]] and [[jasper]]) washed up by the river. A few volcanic rocks and wood fragments seem to have been modified into heavy duty chopping tools.<ref name=Bartstra1988/> In 1973, the nearby Sambungmacan site yielded a unifacial [[chopper (archaeology)|chopper]] (as well as a flake) made of andesite.<ref name=Bellwood1997/><ref name=Semah2014/> Because of how few tools have been recovered, it is impossible to categorise Solo Man into any distinct [[industry (archaeology)|industry]].<ref name=Bellwood1997/><ref name=Semah2014/> Like many other Southeast Asian sites predating modern humans, the Ngandong site lacks sophisticated choppers, [[hand axes]], or any other complex chopping tool characteristic of the Acheulean of Western Eurasian and African sites. In 1948, Movius suggested this was because of a great technological divide between western and eastern ''H.&nbsp;erectus'' (the "[[Movius Line]]") caused by a major difference in habitat (open area vs. tropical rainforest), as the chopping tools are generally interpreted as evidence of big game hunting, which he believed was only possible when humans spread out onto open plains.<ref name=Bartstra1988>{{cite journal|last1=Bartstra|first1=G.-J.|last2=Soegondho|first2=S.|last3=van der Wijk|first3=A.|year=1988|title=Ngandong man: age and artifacts|journal=[[Journal of Human Evolution]]|volume=17|issue=3|pages=332–335|doi=10.1016/0047-2484(88)90074-7 |bibcode=1988JHumE..17..325B }}</ref>

[[File:Biface Extension.png|thumb|upright=1.3|alt=Map showing the general distribution of Middle Pleistocene handaxes |General distribution of [[Middle Pleistocene]] [[handaxes]] according to the archaeological record{{legend|#740|Areas with handaxes}}{{legend|#ada|Areas without handaxes}}]]
Though a strict "Movius Line" is not well supported anymore with the discovery of some hand axe technology in Middle Pleistocene East Asia, handaxes are still conspicuously rare and crude in East Asia compared to western contemporaries. This has been explained as: the Acheulean emerged in Africa after human dispersal through East Asia (but this would require that the two populations remained separated for nearly two million years); East Asia had poorer quality raw materials, namely [[quartz]] and [[quartzite]] (but some Chinese localities produced handaxes from these materials and East Asia is not completely void of higher-quality minerals); East Asian ''H.&nbsp;erectus'' used biodegradable bamboo instead of stone for chopping tools (but this is difficult to test); or East Asia had a lower population density, leaving few tools behind in general (though demography is difficult to approximate in the fossil record).<ref>{{cite journal|first1=S. J.|last1=Lycett|first2=C. J.|last2=Bae|year=2010|title=The Movius Line controversy: the state of the debate|journal=[[World Archaeology]]|volume=42|issue=4|pages=526–531|doi=10.1080/00438243.2010.517667|jstor=20799447|s2cid=2209392}}</ref>

===Possible cannibalism===
In 1951, Weidenreich and von Koenigswald made note of major injuries in Skulls&nbsp;IV and VI, which they believed were caused by a cutting instrument and a blunt instrument, respectively. They bear evidence of inflammation and healing, so the individuals probably survived the altercation. Weidenreich and von Koenigswald noted that only the skullcaps were found, lacking even the teeth, which is highly unusual. So, they interpreted at least Skulls&nbsp;IV and VI as victims of an "unsuccessful assault", and the other skulls where the base was broken out "the result of more successful attempts to slay the victims," presuming this was done by other humans to access and consume the brain. They were unsure if this was done by a neighbouring ''H.&nbsp;e.&nbsp;soloensis'' tribe, or "by more advanced human beings who would have given evidence of their 'superior' culture by slaying their more primitive fellowsman". The latter scenario had already been proposed for the Peking Man (which has similarly conspicuous pathology) by French palaeontologist [[Marcellin Boule]] in 1937. Nonetheless, Weidenreich and von Koenigswald conceded that some of the injuries could have been related to the volcanic eruption instead. Von Koenigswald suggested only skullcaps exist because Solo Man was modifying skulls into [[skull cups]], but Weidenreich was sceptical of this as the jagged rims of especially Skulls&nbsp;I, V, and X are not well suited for this purpose.<ref name=Weidenreich1951/>{{rp|238–239}}

[[Human cannibalism|Cannibalism]] and ritual [[headhunting]] have also been proposed for the Trinil, Sangiran, and [[Mojokerto child|Modjokerto]] sites (all in Java) based on the conspicuous lack of any remains other than the skullcap. This had been reinforced by the historic practice of headhunting and cannibalism in some modern Indonesian, Australian, and Polynesian groups, which at the time were believed to have descended from these ''H. erectus'' populations. In 1972, Jacob alternatively suggested that because the base of the skull is weaker than the skullcap, and since the remains had been transported through a river with large stone and boulders, this was a purely natural phenomenon. As for the lack of the rest of the skeleton, if tiger predation was a factor, tigers usually only leave the head since it has the least amount of meat on it. Further, the Ngandong material, especially Skulls&nbsp;I and IX, were damaged during excavation, cleaning, and preparation.<ref>{{cite journal|first=T.|last=Jacob|author-link=Teuku Jacob|year=1972|title=The Problem of Head-Hunting and Brain-Eating among Pleistocene Men in Indonesia|journal=Archaeology and Physical Anthropology in Oceania|volume=7|issue=2|pages=86–89|jstor=40386169}}</ref>

==See also==
* [[Archaic humans in Southeast Asia]]
* ''[[Gigantopithecus]]''
* ''[[Meganthropus]]''
* [[Peopling of Southeast Asia]]

==References==
{{Reflist}}

== External links ==
* [http://humanorigins.si.edu/evidence/human-evolution-timeline-interactive Human Timeline (Interactive)] – [[Smithsonian Institution|Smithsonian]], [[National Museum of Natural History]] (August 2016).
{{Human Evolution}}
{{Prehistoric Asia}}
{{Prehistoric technology}}
{{Taxonbar|from=Q1142896}}

{{DEFAULTSORT:Prehistoric Asia}}
[[Category:Homo erectus]]
[[Category:Pleistocene primates]]
[[Category:Pleistocene extinctions]]
[[Category:Prehistoric Indonesia]]
[[Category:Solo River]]
[[Category:History of Java]]
[[Category:Fossil taxa described in 1932]]