Mojokerto Delta, East Jawa

OF Huffman & Y Zaim 2003
Mojokerto Delta, East Jawa: Paleoenvironment of Homo modjokertensis
― First Results
Submitted to Journal of Mineral Technology, v.10, n. 2. The Faculty of Earth
Sciences and Mineral Technology,
Institute Technology, Bandung.
Mojokerto Delta, East Jawa:
Paleoenvironment of Homo modjokertensis―First Results

What characterized Homo erectus habitats on the tropical island of Jawa
(Java)? This question is being addressed by a project led by the authors
and supported by the US-based Leakey Foundation and National Science
Foundation. The hominid discovered at Perning in 1936, Homo modjokertensis,
is the focus of our current research because this fossil is far older than
any other from a maritime paleogeographic setting and may be the oldest
hominid known outside Africa. The following summarizes our findings so far.
Newly found documents from 1936-1938 support the statements of the
discoverers that the discovery was found in situ in Plio-Pleistocene
bedrock. These documents have allowed us to relocate the discovery
site, and examine the stratum in which the hominid was found. The bed
formed as a bar in a swift-flowing river channel on a delta plain of the
ancient Mojokerto Delta (named herein). The local sedimentary sequence
containing the hominid bed provides paleo-environmental information on the
shallow sea, the marine-delta front, the delta plain (flood plain and river
channels), and a long-standing delta interfluve (paleosol) where Homo
erectus might have lived.
Test excavations at the hominid site during 2001 and 2002 field seasons
produced 250 fossil vertebrates. The nature of the recovery suggests that
additional hominid remains may be found in the bed.
Fossils from the excavations and nearby surface collecting suggest that
deer, muntjak, bovids, pig, hippopotamus, rhinoceros, Stegodon, and large
cat inhabited the delta, together with Homo erectus.
Mollusks, turtle and crocodile were recovered from the excavation, and
inhabited the river. The fossil of a giant tortoise was recovered from a
nearby locality.
Pollen, spores and phyoliths from the hominid-producing sequence show that
mangroves existed along the seacoast, swamps occurred along the river, and
the distant mountains were forested. The delta plain included―and perhaps
was largely covered with--grasslands. Stable-carbon isotope signatures
(δ13C) have been obtained from the enamel of teeth of bovids, cervids, and
other animals from the hominid bed and other localities in the
hominid-bearing sequence in the Perning district. This is the first use the
stable-isotope method to characterize the paleoenvironment of Homo erectus
in Jawa. The results encourage the more widespread use of the technique.
Most of the carbon isotope results fit the C4 photosynthetic pathway
characteristic of tropical grasses. This result is consistent with the
grasslands indicated by pollen and phyoliths.
The good state of preservation of Homo modjokertensis relative to the
high-energy fluvial sediment in which it was found indicates that the skull
probably was transported a short distance from its life habitat,
and therefore H. erectus was likely to have been a member of the community
of animals that lived in the Mojokerto Delta. The delta contained a variety
of potential hominid foods. Fossil evidence for large terrestrial mammals,
mollusks, other aquatic animals, fruit-bearing trees, and an edible fern has
been found so far. Work continues that will allow us to describe the
hominid paleoenvironment and dietary resources of the delta more completely,
as well as to provide an unequivocal absolute age for the Perning hominid.

Mojokerto Delta, East Jawa