Proceedings of the 7th and 8th Symposia on Collection Building and Natural History Studies in Asia and the Pacific Rim,
edited by Y. Tomida et al., National Science Museum Monographs, (34): 289–294, 2006.

Indonesian Homo erectus and Modern Human Origins in Australasia:
New Evidence from the Sambungmacan Region, Central Java
Yousuke Kaifu1, Hisao Baba1 and Fachroel Aziz2
1
Department of Anthropology, National Science Museum,
3–23–1 Hyakunincho, Shinjuku-ku, Tokyo 169–0073, Japan(e-mail: kaifu@kahaku.go.jp, baba@kahaku.go.jp)
2
Geological Museum, Geological Survey,
Jl. Diponegoro No. 57, Bandung 40122, Indonesia(e-mail: azizf@bdg.centrin.net.id)

Abstract Recent fossil and genetic studies generally support the Recent African Origins Theory as
explanatory model of the origins of modern humans. However, the current fossil evidence is still insufficient to reject the competing claim regarding Australasia, that is, the idea of continuity between
Javanese Homo erectus and modern aboriginal Australians. Recent discoveries of new Homo erectus
fossils from the Sambungmacan region, Central Java, shed new light on this issue. Preliminary studies suggest their intermediacy, both chronologically and morphologically, between the earlier andlater groups of Javanese Homo erectus. The evolutionary trajectory of Javanese Homo erectus depicted from the more complete fossil record including the Sambungmacan specimens supports discontinuity between Homo erectus and Homo sapiens in Australasia.
Key words:

Homo erectus, modern human origins, Sambungmacan, JavaIntroduction
Recent advances in fossil and genetic studies now almost unanimously support the Theory of
Recent African Origins of modern humans, although the question of the degree of admixture between dispersing Homo sapiens populations and local archaic hominids in Eurasia is still debatable (Stringer, 2002). However, this establishment of the overall picture does not mean that all thequestions raised by the alternative hypothesis called Multiregional Theory have been answered
unequivocally.
Among such questions is the possible contribution of Homo erectus in Australasia to the formation of modern aboriginal Australians. There are two major reasons for the multiregionalists
to support this possibility: (1) The lineage of Indonesian Homo erectus was never an example ofevolutionary stagnation. The brain size in this lineage had been increased slowly but steadily, toward the same direction as Homo sapiens. (2) There are several unique characteristics shared between Indonesian Homo erectus and fossil and modern Homo sapiens in Australia (Wolpoff,1999; Hawks et al., 2000).
Supporting evidence for the Recent African Origins theory is given mainly from different
points of view. For example, Swisher et al. (1996) raised a possibility that the Homo erectus fromNgandong, the chronologically youngest Indonesian Homo erectus so far known, may have coex-290

Y. Kaifu, H. Baba and F. Azizsisted with Homo sapiens in Indonesia around 50–30 thousand years ago. If confirmed, thiswould make the evolution from the former to the latter unlikely, but these suggested dates for theyoungest Homo erectus fossils have constantly been questioned (Grun and Thorne, 1997; Matsu’ura et al., 2000; Antón, 2003; Westaway et al., 2003)
Other disputes to the multiregional way of thinking are on the interpretation of morphological characters in fossil specimens. Many of the characters quoted as supporting evidences forevolutionary continuity between Homo erectus and aboriginal Australians (Thorne and Wolpoff,
1981) are revised and re-interpreted in different ways, following the new reconstruction of one of
the key fossil specimen of Javanese Homo erectus, Sangiran 17 (Aziz et al., 1996). One fossil
cranial vault of Homo sapiens from the Willandra Lakes, southeastern Australia, has attracted
particular attention of multiregionalists because this specimen, WLH 50, shows general robusticity and other peculiar characters that recall the Indonesian Homo erectus (Hawks et al., 2000).
However, many researchers think this specimen is pathologically deformed and thus cannot serve
as evidence of evolutionary continuity (Brown, 1989; Webb, 1990; see also Stringer, 1998, andWestaway, 2006). Also, contrary to the expectation of the Multiregional Theory, the date of WLH
50 is younger than other more gracile (and thus less similar to Homo erectus) Homo sapiens fossils from Australia (Brown, 1992; Stone and Cupper, 2003).
In summary, morphological primitiveness of Javanese Homo erectus and its possible late survival, and other contradictions in specific points of the Multiregional Theory have been the major
reasoning of phylogenetic discontinuity between the two groups. However, the current evidencesof morphological discontinuity in the fossil record of Australasia are far more ambiguous compared to those documented in Europe between the Neandertals and Cro-Magnon (Mellars, 2004).
Further evidences are needed to obtain a clearer picture of the modern human origins in Australasia.
In order to evaluate evolutionary continuity or discontinuity in Australasia, it is important todocument not only the primitiveness of chronologically younger Javanese Homo erectus, but also
evolutionary trajectory in this lineage. If such trajectory directs toward the morphology of Homosapiens (particularly aboriginal Australians), then the Multiregional Theory gains support. Onthe contrary, if such trajectory is different from the way toward Homo sapiens, it becomes more
likely that this Javanese lineage was virtually evolutionary dead end.
The Site of Sambungmacan
Indonesian Homo erectus is best represented by the fossil remains from the Early Pleistocene
sediments of Trinil and Sangiran, and those from the Middle or Late Pleistocene terrace depositsof Ngandong. However, these two groups are thought to be chronologically separated for morethan 500 thousand years. Also, there are some distinct morphological differences between them
(Weidenreich, 1951; Santa Luca, 1980). Thus, some fossils that fill this chronological and morphological gap are needed to document evolutionary trajectory in Javanese Homo erectus. Suchcandidates have recently recovered from the Sambungmacan region.
The Pleistocene deposits of the Sambungmacan District, Central Java, have so far yielded
four hominid fossils from two localities. One is located at a canal constructed to control seasonal
flooding at a meander site of the Solo River. The other is located 4 km to the east (upstream) of
the canal site, at another meandering site of the Solo River (Figs. 1, 2).
At the canal site, the first specimen, the Sm 1 skull, was found in 1973 by local workers during the construction of the canal (Jacob, 1996). The second specimen, Sm 2, a mid-shaft of theHomo erectus and Modern Human Origins in Australasia

Fig. 1.

291

The Sambungmacan canal site (left) and the discovery site of Sm 3 and 4 (right).

Fig. 2.

Three skulls discovered from Sambungmacan. a, Sm 1; b, Sm 3; c, Sm 4.

right tibia, was found in 1977 from the surface collection of vertebrate fossils at the canal site
(Baba et al., 1990). In 1997, another skull was discovered by a local worker who was collecting
sand from the river bed of the Solo River, about 4 km upstream from the Sambungmacan canalsite (Boedhihartono, 1998; Márquez et al., 2001). This skull, Sm 3, had later been brought toNew York by an unknown broker, but was returned to Indonesia in 1999. The statement of local
workers and our survey around the alleged findspot indicate that Sm 3 had derived from an outcrop somewhere upstream, and been flown down to the site. In October 2001, one more new, virtually complete cranial vault of Homo erectus was discovered, again, during the sand collection
activity by local workers (Baba et al., 2003). This specimen, Sm 4, is unique in its exceptionally
good state of preservation. Most of the important surface characters can be assessed with certain-292

Y. Kaifu, H. Baba and F. Azizty, and this would helps evaluating morphological details in other Homo erectus skulls with varying degree of damages.
Among these discoveries from Sambungmacan, Sm 2 is heavily mineralized and thought tohave been derived from the earlier Pleistocene deposits (Matsu’ura et al., 2000). However, at thepresent state of the research, chronological positions of the three Sambungmacan skulls are notyet certain. Swisher et al. (1996) reported the age of Sm 1 as about 30 to 50 thousand years ago.
However, the findspot of the specimen is not clear and there remains significant doubt about theassociation of the dated bovid tooth with the hominid skull.
Sm 3 and 4 are considered to have been flown down from outcrops somewhere upstream. Thesediments of this area are composed of multiple layers of different ages. The animal fossils accumulated at the findspot of Sm 3 show various colors and degree of fossilization. Thus, it is clearthat these fossils had been derived from multiple sources of varying ages. The preservation of thetwo skulls is also clearly different. Sm 4 is dark brown in color, and exceptionally well-preserved.
On the other hand, Sm 3 is darker and surface damage is more extensive. In spite of these complicated factors, it is still possible to narrow down the possible sources of these skulls.
In the 1990’s, a Indonesian and Japanese research team surveyed the Sambungmacan area
and reported that most of the recorded outcrops of the region belong to the Middle Pleistocene
Kabuh Formation (Hasibuan et al., 1995). In addition, the iron bearing sand being collected bylocal people at the finding site of Sm 3 and 4 shows high content of magnetite and hornblende
crystals with small amount of hypersthene, plagioclase and pumice ball. This is a characteristicof the so-called “Kabuh Sand”. Thus, both Sm 3 and 4 likely had derived from the Kabuh Formation, and probably they are older than the Ngandong hominid remains. We infer that Sm 1 also
derived from a similar context.
Morphology of the Sambungmacan Skulls
Our extensive comparative analyses indicated that the Sambungmacan skulls, as a group,
show intermediate morphology between the earlier and later Javanese Homo erecuts, while retaining a series of unique features of Javanese Homo erectus as a whole (Baba et al., 2003). We
examined and compared most of the major cranial remains from Sangiran, Sambungmacan, andNgandong. All these Indonesian specimens show a set of characteristic features which is notshared with Chinese Homo erectus represented by the Zhoukoudian remains. Such features include a comparatively straight supraorbital torus, the lack of a continuous supratoral sulcus, and atransversely wide occipital bone.
Based on a review of the previous works and our own observation, we identified 22 characters that differ between the earlier (Sangiran) and later (Ngandong) Javanese Homo erectus(Table 1). There may be some degree of inter-character correlations among these items, and thenumber of characters showing similarities or differences in Table 1 does not necessarily reflect
the “genealogical closeness” among the three groups. However, at least, overall intermediate tendencies of the Sambungmacan skulls are apparent.
These results suggest continuous regional evolution of the lineage of Javanese Homo erectus
without significant contact with other archaic Homo populations in the surrounding regions suchas northern China (Baba et al., 2003; see also Antón, 2002, and Kidder and Durband, 2004). In
other words, Javanese Homo erectus was probably substantially isolated from other hominidgroups in the Asian mainland such as the Peking Man.
At the same time, Table 1 suggests the existence of several unique morphological specializa-

Homo erectus and Modern Human Origins in Australasia

293

Table 1. State of differential morphological characters between Homo erectus crania from Trinil/Sangiran and Ngandong, and phenetic condition of the Sambungmacan specimens.
Trinil/Sangira
1. Cranial capacity (cc)813–1059
2. Relatively high vault()3. Moderately swollen frontal squama and posterior parietals
4. Postorbital constriction weaker
5. Strong temporal gutter
6. Reduced relative area of temporal muscle attachment

7. Extremely linear supraorbital torus in front view
8. Laterally thickened supraorbital torus
9. No supraglabellar depression with right and left supratoral planes discontinuous
10. Extensive, plateau-like angular torus()
11. Antero-posteriorly elongated parietal incisura
12. Wide supramastoid sulcus

13. Large mastoid with triangular base
14. Specialized mandibular fossa morphology

15. Well-developed tympano-mastoid fissure()
16. Less extensive digastric fossa associated withwell-developed paramastoid crest
17. Vertically set occipital squama
18. Marked projection of occipital torus()19. Lower arm of occipital torus stronger than the upper
20. Excavated nucal planum
21. Opisthionic recess of foramen magnum
22. Strong postcondyloid tuberosity


Sm 1

Sm 3

Sm 4

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Symbols  and  indicate presence and absence of the characters, respectively. Parentheses indicate notably variable condition, “int” is intermediate.

tions in later Indonesian H. erectus. Although further investigation is needed to confirm their true
peculiarities among hominids, we suppose such specialized features include the characters 7–10,14, 16, 18, and 20–22 of Table 1. Modern Australians apparently lack these unique features of Indonesian Homo erectus, and share characteristics of Homo sapiens with modern humans in otherregions of the world. This observation supports the hypothesis that the lineage of Indonesian
Homo erectus went extinct without significant contribution to the ancestry of modern humans.
Summary
The Sambungmacan region, which has recently yielded three well-preserved Homo erectus
skulls, is a promising paleoanthropological site. The original stratigraphic positions are more orless unclear for all these hominid specimens. However, because the number of the outcrops along
the river is limited, it would not be impossible to locate the original stratigraphic levels of the hominid fossils. Information available at present suggests that Sm 3 and 4 are from the Kabuh Formation, and a future study could further narrow down the potential sources of these and other
Smabungmacan fossil specimens. The Sambungmacan hominid remains are important because
they probably fill the gap existed in the previous fossil record of Javanese Homo erectus. The results of our comparative analyses suggest that they represent the middle phase of the evolutionary
trajectory of Javanese Homo erectus that had continued from the earlier Early Pleistocene. The
morphological specialization seen in the late group of the lineage suggests that Javanese Homo294

Y. Kaifu, H. Baba and F. Azizerectus was substantially isolated and made minimal contribution to the ancestry of modern humans in Australasia.
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