Australia: The Land Where Time Began

A biography of the Australian continent 

Ngandong Site – Variability of Homo erectus in Java

According to Ayala & Cela-Conde the great degree of variability of Homo erectus in Java is probably due to different aspects with local – geoecological –patterns as well as temporal patterns, though it may also be the result of sexual dimorphism and even individual characteristics.

However, the difference of morphology between specimens from older and younger age recovered from Sangiran suggests a process of phyletic evolution. The 2 questions to settle are:

1.     Whether this evolution would affect the uniformity of the species so that it would indicate the presence of 2 distinct chronospecies; and

2.     Whether the late Java specimens might be considered to be members of the same “archaic” sapiens’ grade, marking the transition from Homo erectus to Homo sapiens.

The different species that were proposed for the specimens from Java that were more modern was based on the exemplars from the Ngandong site, which are some of the most recent in Java. Up to 12 skulls that were recovered in Ngandong were classified as Homo soloensis (Oppennoorth, 1932). Included in this sample were massive-looking skulls with large cranial capacity averaging 1,200 cc. Specimens recovered from other sites in Java that are of a slightly older age, and with a cranial volume that was slightly lower, support the idea of a single taxon that was evolving. That is the case with Sm 4, the exemplar from Sambungmacan , which is a sizeable calotte that has a volume of 1,006 cc, and is probably a male, that was discovered in 2001, who had a general appearance is typical of the H. erectus from Java (Baba et al., 2003). This fossil is preserved very well, which allowed the observation that the flexion of the base of the skull is similar to that of modern humans, a condition associated with Olduvai OH 9, though because of the poor state of preservation of the Olduvai specimen there is some uncertainty. After a study of Sm 4, it was concluded (BaBa et al., 2003) that Sm 4 is intermediate between the samples from Trinil/Sangiran and that from Ngandong.  Contrary to this view it was argued (Zeitoun et al., 2010) that the evolutionary change from Homo erectus in Java would have led to a new species on the island.

A morphological study (Manzi, Bruner & Passarello, 2003) brought BOU-VP-2/66 closer to KNM-ER 3733 and 2883, asserting that their belonging to Homo ergaster is supported by all of them, while OH 9 and Dmanisi specimens and the Homo erectus from Ngandong in Java would be intermediate exemplars in human evolution.

Beginning 780 ka the Middle Pleistocene was the time of the latest evolutionary events of our lineage; the events were complete when the modern humans had become the prevalent species, approximately 30,000 years ago. Included in this time range are the end of the Mindel glaciation, 750 ka, the next 2 glaciations, Riss & Würm, and their corresponding interglacial periods. Though these climatic changes were global, they did not affect Africa, Asia and Europe to an equal extent. Therefore, in each continent the evolutionary events had distinctive features. The situation at the end of the Upper Pleistocene was, however, shared by the whole of the ancient world: Homo sapiens was the only species of its kind to survive. The transition from the ancestral species from the Middle Pleistocene to modern humans has been explained traditionally by 2 opposing hypotheses. The first is the:

1)    “Multiregional Evolution Hypothesis” or “Hybridisation Hypothesis” (Multi Hypothesis or MH onwards; inspired by the work of Franz Weidenreich (1943), which suggests that evolutionary changes happened contemporaneously in different regions of the world. His study (Weidenreich, 1943) focused in particular on specimens of Zhoukoudian and their possible evolution to Homo sapiens, though the most solid evidence favouring the multiregional model are the common traits that have been detected in the last Homo erectus in Java, those of Ngandong, and the first modern humans of Australia (Antón et al., 2011). As has been argued (Wolpoff, Hawks & Caspari, 2000) “multiregional” does not mean there were independent multiple origins, or an ancient divergence that occurred of modern human populations, or the simultaneous appearance of adaptive traits in various regions, or parallel evolution. The assumption that underlies MH is the existence of a global network of genes being exchanged between evolving human populations in continuous contact (Wolpoff et al., 2000), with the result that the unity of species would be preserved without divergence.

2)    The “Out of Africa Hypothesis” or “Replacement Hypothesis” (Replacement Hypothesis or RH onwards), is based, first, molecular studies (Cann et al., 1987; Vigilant et al., 1991). This hypothesis suggests that the location of the transition from Home erectus to Home sapiens was in a population that was fairly localised in East Africa. No genetic contribution would have been made to the appearance of H. sapiens by Asian hominins of H. erectus grade. In Asia H. erectus sensu stricto remained relatively unchanged until anatomically modern humans replaced them, or they simply disappeared, so that their territories were occupied by migrating Homo sapiens.  Homo neanderthalensis, a different species, occupied the Near East and Europe It was also eventually displaced, or substituted by, by anatomically modern humans.

The beginning of the transition process to Homo sapiens is related to various species in Africa, Asia and Europe, as has been stated previously. All of these taxa display certain morphological; features, as well as being relatively contemporary. Compared with Homo erectus, their crania display:

·        Greater capacity, in most instances.

·        Higher cranial vault.

·        Expansion of the parietal region.

·        Reduced prognathism, the frontal projection of the face.

Among the diverse aforementioned taxa, of course, there are differences. Also, there is some level of doubt concerning their age, given that many of the fossils were recovered a long time ago, and their location was in places that were difficult to date with the techniques that were available at the time. Their assignation at the time of their discovery to different species is accounted for by these circumstances. E.g., remains from Europe were assigned to Homo heidelbergensis (Schoetensack, 1908), Homo erectus petraloniensis (Murrill, 1975), and Homo swanscombensis (Kennard, 1042). Over the same period a number of other fossil discoveries were given names such as Homo rhodesiensis (Woodward, 1921) and H. helmei in Africa, Homo (Javanthropus) soloensis (Oppennoorth, 1932) in Asia, among other taxonomical proposals.  More parsimonious solutions were suggested as it became apparent that certain common characteristics were shared among them. Historically speaking, the first was to place them all into Homo erectus, noting that in each case the specimen was an evolved form of Homo erectus, though did not justify a new species. This taxonomic solution is part of the “single species” of Homo erectus that was proposed by Milford Wolpoff (Wolpoff, 1971a). However, the presence of Home erectus in Europe was opposed by a number of authors (Stringer, 1984, 1985; Stringer, Hublin & Vandermeersch, 1984), as well as others. The different specimens that dated to the early Late Pleistocene were considered to be predecessors of Homo sapiens, with no further detail. Therefore, given the lack of such specification, they were designated informally as “archaic” Homo sapiens (Stringer, 1985; Bräuer, 1989). The proposal of archaic humans was initially related with European human evolution.

The transition in Java

The permanence of Homo erectus

In the Solo River Valley12 cranial remains were discovered in the Ngandong site at the beginning of the 1930s, Ngandong 1-8 and 11-14, of which Ngandong 7 was the most complete, 2 tibias, Ng 9 and Ng 10, which were recovered from a sedimentary terrace 20 m over the current river bed (“terrace 20 m”. The age of the Ngandong specimens has continued to be controversial. The levels which the fossils are believed to have come from have fauna and geomorphology that correspond to the Upper Pleistocene, though the morphological comparisons that were carried out with other similar specimens, as well the suspicion that the fossils may have been moved from their original stratum, has led to their placement within the Middle Pleistocene  (Santa Luca, 1980). It has been estimated (Teuka Jacob, 1975) that they would have been between 400,000 and 200,000 years old.

Electron spin resonance and mass spectrometry were used in uranium series (ESR/U) on bovid teeth from the same level as the hominin specimens (Swisher et al., 1996) giving an age range of 53,300 ± 4,000 to 27,000 ± 2,000 years for Ngandong and Sambungmacan. Earlier studies using the same dating techniques (Bartstra e et al., 1999; van der Plicht, 1989) reduced the figures to 70,000-30,000 BP, though they do not pose a serious discrepancy. These dates were criticised, however (Grün & Thorne, 1997), indicating 2 possible errors. It was claimed that Swisher et al. (1996) had made an improper use of ESR techniques. The other claimed error is that it is not correct to apply an age obtained by dating bovid teeth to the human specimens, because the upper terrains of the Solo River – such as “terrace 20 m” – are comprised of a mixture of materials originating in different locations and of different ages. It was argued (Grün & Thorne, 1997) that the colour of the hominin bones and the fauna fossils do not match; therefore they are of different ages. In response to these criticisms, however, Swisher et al. (1997) defended their technical procedures, referring to the continuous interpretation, that were indicated by Gert-Jan Bartstra (1988) – granting the same age to the hominins as to the remainder of the faunal fossils of Ngandong.

Radiometry, the ⁴⁰Ar/³⁹Ar method, was used for the first direct estimation of the age of Ngandong (Indriati et al., 2011). The age obtained was, on average, 546,000 ± 12,000 BP, which placed the specimens later than the first Homo erectus from Java, those from Sangiran, but at a time that was much older than that proposed by Swisher et al. (1996).

The controversy with the dating and the difficulty of comparing the fauna from Java, which was subject to the isolation that is imposed by an island, with other localities that are continental, disappears if the samples being analysed are those of the hominin fossil remains whose age is being determined. The gamma-ray spectroscopy technique was used (Yokoyama et al., 2008) who determined an age for the Ngandong fossils of between70,000 and 40,000 BP, which is closer to the estimated age that had been determined previously (Swisher et al., 2008) than that had been determined by Indriati et al. (2011). It has been noted (Antón, 2003), while not disregarding the doubts regarding the origins of the specimen terrains , in her study on the natural history of  Homo erectus that are supported by the available data, an age of Late Pleistocene for both Ngandong hominins and the remainder of the fauna. This is the conclusion that has been accepted by Francisco & Cela-Conde.

As well as the age of the specimens, the basic issue in interpreting the evolutionary meaning of late specimens from Java is their morphology, especially in comparison with the remainder of the sample from the island. The description (Antón, 2003) of the Ngandong and Sambungmacan specimens indicated as the feature that is the most outstanding, apart from the large volume, is the shape of the cranium, that has a moderate supraorbital constriction, though retaining the area of wider expansion towards the back, a trait that is shared with the oldest specimens of the island. The cranial vault is long and fairly low in lateral view. A continuous torus in displayed on the rear side. The large or moderate sized torus displayed on the rear side. The glabellar torus is continuous and of large or moderate size. When taken together it is indicated by these features that these specimens from Java maintained an overall structure that had not changed very much with the exception of the size of the cranium, which became larger in most modern fossils.

Morphological proximity of Homo erectus to Homo sapiens in Java

The specimen Sm 3 is the focus of the more detailed study on the existing morphological relations between the late Homo erectus in Java and the oldest specimens of Homo sapiens. The specimen Sm 3 is a Sambungmacan calotte lacking the face. This specimen was found in 1977 and remained part of the inventory of an antiques’ shop in Jakarta until secretly removed from Indonesia in 1998, and appeared in 1999 in a natural history curiosity shop in New York. Márquez et al. indicate with near certainty that it was discovered near Ngadirejo, located between Chemeng and Poloyo (Márquez et al., 2001).

The specimen was named Homo erectus newyorkensis (Laitman & Tattersall, 2001) in the introduction to the first studies in recognition, supposedly ironically, of its presence in Manhattan. Whatever the reason for the name Francisco & Cela-Conde believe the proposed name should be taken as formal from the standpoint of the criteria of the agency that oversees the use of a correct taxonomy, the International Commission on Zoological Nomenclature (ICZN).

The comparative study of Sm 3 (Delson et al., 2001) used morphometric techniques – procrustean markings – that were applied to the localisation corresponding to the points of the glabella, bregma, lambda, inion, and opisthion, in a sample of Homo erectus Indonesia, China, and Kenya, “archaic” sapiens from Kabwe and Petralona, and 10 modern human crania. It was shown by statistical analysis (main component and canonical discrimination) in all cases that Sm 3 is in an intermediate position between the other fossil groups and the current samples. Sm 3 was brought closer to other specimens from Sambungmacan (Sm 1; Jacob, 1975) and Ngandong, by the morphological comparison. The differences with other Homo erectus, in particular, related with a less projected glabella in anterior direction, a more vertical supraorbital plane, and a less angular occipital torus (Delson et al., 2001). However, a female is suggested by the gracility, so those differences might partially correspond to sexual dimorphism.

A study was conducted on Sm 3 endocranium (Broadfield et al., 201) on the Sm 3 using a CT scanner, as well as traditional methods, which was made possible by the excellent condition of the calotte. Some features indicated a striking degree of modernity: the degree of asymmetry between the 2 hemispheres, with petalia in the left occipital and the right frontal, though in essential traits the specimen shares a neurological structure with other homo erectus from Java and China. The frontal lobe is rounder and shorter, which contrasts with the flat, elongated lobe of other Homo erectus from Java, such as Sangiran 17. The endocranium of Sm 3 displays different morphology than those present in the fossil hominin record, according to Broadfield et al. (2001), which increases the great degree of Homo erectus in Indonesia.

The Ngawi I cranium is another remarkable specimen that was discovered in August 1987 by peasants in a river bank just outside the town of Selopuro (Ngawi, Java, Indonesia (Widianto & Zeitoun, 2003). The circumstances of its discovery make it infeasible to achieve accurate localisation and dating, though its origin was attributed to the Pitu terraces (Watualang, west of Ngawi).

Ngawi I is a cranium that is almost complete, though somewhat eroded, which shows part of the face, but is missing the maxillar or mandible. It was separated from the Trinil-Sangiran group in the first description and interpretation of the fossil (Widianto & Zeitoun, 2003), and was considered to be comparable to the Ngandong-Sambungmacan group. Authors disagreed over its best taxonomic consideration. It was argued by Widianto to be part of an advanced grade of Homo erectus, though it was preferred by Zeitoun to either rehabilitate the name Homo soloensis or to attribute the fossil to a Homo sapiens subspecies. Both argued, however, it should be given the same consideration to Ngawi I and the specimens from Ngandong-Sambungmacan. The possibility of dividing the specimens of Homo erectus from Java into 2 different species was left open in a subsequent study (Zeitoun et al., including Widianto, 2010).

A multivariate analysis (Durband, 2006) of a full sample of specimens of Homo erectus from Africa, Indonesia and China showed how close morphological similarities were between Ngawi I and the Ngandong and Sambungmacan specimens, as had been concluded (Widianto & Zeitoun, 2003). When the range of the comparisons is expanded, however, Ngawi I begins to appear very close to Homo erectus from Java, which includes the oldest Sangiran, and becoming more different from the Zhoukoudian specimens. According to Durband (2006), it is implied by this observation that there was a characteristic population in Java that developed and maintained its own derived traits, thereby becoming different from the majority of Chinese Homo erectus, with some exceptions like the Hexian exemplar.

Evolutionary meaning of the advanced specimens of the Homo erectus from Java

The question of whether to uphold the idea that a taxon, Homo erectus, continued in Java for such a long time with no variation prior to the arrival of Homo sapiens, or whether it might be necessary to propose a different evolutionary model, has been raised by the features of the specimens from Ngandong, Sambungmacan, and Ngawi that are somewhat advanced.

The possibility has been suggested, based on the large cranial capacity of the specimens from Ngandong, that Ngandong could be transitional from Homo erectus to Homo sapiens. There are several conflicting views, as in the case of “archaic” specimens. Therefore, the initial idea of Ngandong specimens being a new species was followed by the later specimens being attributed to a variety of Neanderthal (Vallois, 1935; von Koenigswald, 1949). Examination (Weidenreich, 1933) brought the Solo fossils closer to Homo erectus, though without proposing any classification for them. It was claimed following a detailed study (Santa Luca, 1980) that the Ngandong specimens were similar to those from Trinil and Sangiran so should be classified as Homo erectus. Size differences as well as other features could be due to sexual dimorphism (Ng 6, which was considerably larger, was a male, and Ng 7, which was smaller, was a female).

A comparative analysis of traits from the base of the cranium was carried out (Durband, 2007), such as the foramen morphology, the placement of the squamo-timpanic fissure in the temporomandibular fossa, and the extreme expression of the post-condyloid tubercle, all characters that were mentioned by several authors, such as Franz Weidenreich and Teuku Jacob, in order to assess any possible relationships between the Sangiran Homo erectus, the more advanced specimens from Ngandong, and the Australian Aboriginal people of the present, relationships which are considered to be indicative of evolutionary continuity by supporters of MH. There features, which are present in the Ngandong population (Durband, 2007) were concluded to be lacking elsewhere, which supports the idea of discontinuity at this stage of evolution in Australasia.

At the same time, the modernity of the frontal and parietal areas of Sm 3could be interpreted as being evidence of an ancestral relationship with Homo sapiens. A similar result from the CT scans of the Sm 4 specimen was obtained (Baba et al., 2003). According the authors, an independent evolution of the parietal and occipital region is indicated by the basicranial flexion, which lacked a well-developed torus, and a low vault. But evidence of a phylogenetic link between Homo erectus and Homo sapiens was not seen in the intermediate condition of Sambungmacan specimens (Broadfield et al., 2001; Baba et al., 2003). The morphology of late specimens from Java, in contrast, indicates to these authors that these are populations that are substantially isolated. It should be remembered that the separation of the glabellar torus into 2 arches was already present in the KNM-ER 42700 specimens from Koobi Fora.

The great variation of Homo erectus in Java probably follows different aspects with both local (geo-ecological) as well as temporal, sexually dimorphic, and even individual patterns. However, it doesn’t seem likely that there should be a large intraspecific variability within one and the same population: option 1by Márquez et al. (2001). The work of synthesis of biometric, morphometric, and cladistics approaches (Zeitoun et al., 2010) concluded that on this basis the late specimens from Java can be considered to be a separate species from Homo erectus, a position which corresponds with option 2 (Márquez et al., 2001), with its first proposed name being Homo soloensis. It has been pointed out (Antón, 2003), however, that in Java the major differences between ancient and modern forms of Homo erectus are related to the cranial size increase in the modern form which affects the height of the vault and decrease of the post-orbital constriction. For Antón (2003) many of the features that are listed as being distinctive in the specimens from Ngandong with respect to Homo erectus – the morphology of the supraorbital torus, occipital, mastoid, and supramastoid – are actually differences between the entire sample from Java and the Chinese sample. Based on this idea, if the enlargement of the skull present in the late specimens is ignored, it is found that the Javanese population, broadly associated with Homo erectus, forms a morphologically close group that contrasts with the Homo erectus from the Asian mainland.

Whatever the case it is shown by the cranial increment that an evolutionary stasis with no evolutionary changes in this taxon in Asia is not correct, a stance which was previously supported (Wolpoff, 1984) by way of a comparative analysis of the cranial, mandibular and dental features from a sample of 92 specimens. An evolution of the first populations of Homo erectus to forms with a larger cranial size is likely, as also happened in Europe with the Neanderthals and in Africa with modern humans, even if the transition to anatomically modern humans did not take place on Java. This would be another case of parallelism. In order to explain the differences between the Asian transition process, and the European and African, Francisco & Cela-Conde continue to speak of a stasis of H. erectus in Asia.

Sources & Further reading

1. Ayala, Francisco J. & Cela-Conde, Camilo J., 2017, Processes in Human Evolution: The Journey from early hominins to Neanderthals and modern humans, 2^nd edition, Oxford University Press