Understanding Sundaland

Tauhid Nur Azhar

Photo by Pukpik on Unsplash

After enjoying the pink sunset on the mezzanine of the house, a WhatsApp message came in the Sinau Peradaban group. The sender was Mr. Janu Dewandaru, one of the deans at the Bank Indonesia Institute. The content was information from the results of discussions about the existence of Sundaland.

Fragments of the ancient continent Gondwana whose existence greatly influenced the development of human civilization, and is closely related to human migration (Homo sapiens). Sundaland itself is now part of Southeast Asia and of course the archipelago.

Changes in sea level during the Holocene caused by changes in temperature and melting ice at the poles known as the interglacial period gave the final shape of geomorphology and topography of the islands as we know them today.

The name Sundaland (in Dutch: Soendaland) itself was given by Gustaaf Adolf Frederik Molengraaff, a geologist from the Dutch East Indies in 1919. Molengraaff also for his extraordinary contributions in geology, his name is used as the name of an ancient river basin on the Java sea floor.

The Molengraaff river basin consisting of main rivers and tributaries originating in Sumatra, Java and Kalimantan such as Musi, Batanghari, Citarum, Bengawan Solo, Brantas, Kapuas and Barito, became geological evidence that the three main islands of Indonesia were previously one large stretch which was part of Sundaland.

Interestingly, the existence of Sundaland is often associated with the “civilization explosion” of humans which is thought to be caused by the fulfillment of prerequisites related to environmental conduciveness that can become a habitat for constructing intelligent ecosystems. The stable equatorial temperature due to the Coriolis effect and two relatively non-extreme seasons, abundant water resources, tropical rainforests which are biomes with high biodiversity indices, almost unlimited maritime potential, and the existence of a volcanic ring of fire that fertilizes, and an intercontinental position with high geostrategic value.

So that some scholars who are interested in the development of human civilization hypothesize that Sundaland is the starting point for the rise of human civilization (Homo sapiens).

In the Out of Sundaland model proposed by Stephen Oppenheimer and Martin Richards (2001), they argue that the origin of Austronesian speakers is in the Southeast Asian archipelago, based on mitochondrial studies showing high levels of genetic diversity.

Some genetic markers in mitochondrial DNA (mtDNA) such as: hypervariable region 1 sequence in mtDNA D-Loop, polymorphic site restriction pattern encoding genes in mtDNA, 9-bp deletion in the COII/tRNAlys intergenic region, Polynesian motif can be used to study the characteristics of a population. Prehistoric skeletal remains can provide genetic information regarding the history of a population through a molecular approach. (Herawati Sudojo et al., 2001).

There is an interesting fact related to the theory of civilization centers in the archipelago, from multi-institutional research focusing on human genetic profiles and phylogenetic trees, it was found that the population of Madagascar from its 3 main ethnic groups Mikea (hunter-gatherers), Vezo (fishermen), and Merina (highland tribe), have genetic traces referring to close kinship with the Banjar tribe in South Kalimantan.

From research conducted by a joint team coordinated by the Eijkman Institute of Molecular Biology for seven years until 2012, it was found that the original ancestors of the Madagascan population were 28 women from Indonesia who sailed to Madagascar 1,200 years ago. And from subsequent research results it was confirmed that these Indonesian women originated from the Banjar tribe.

One of the researchers in the team was Nicolas Brucato from the molecular anthropology laboratory at the University of Toulouse France, who stated that 40% of the Madagascan genome is inherited from Indonesians.

So it can be concluded that at the end of the Holocene, the migration process out of the former Sundaland region was still taking place.

Data from geografi.org shows that the island of Java which became part of the civilization center in its time, formed around 60 million years ago.

The composition of the basement rocks that form the base of Java island have different ages from one another. In western Java it is estimated to have started forming at the end of the Cretaceous period and became part of the Sunda Shelf, while eastern Java originated from the fragments of the Australian continent (East Java Microcontinent). The eastern part is estimated to have started colliding with the western part around 100–70 million years ago to form the initial shape of Java island.

Java island was under compressive pressure from the south which caused the Indo-Australian oceanic plate moving northward to collide with the Eurasian continental plate from the south.

The oceanic plate which has a higher density underwent subduction and produced a subduction zone. Due to the subduction, oceanic trenches, new mountains, and volcanic activity formed. This uplift also raised part of the sea surface as can now be seen and studied in the Melange Karangsambung formation in Central Java.

There was also melting of material from the Indo-Australian oceanic plate which became magma and created a line of volcanoes parallel to the longitudinal axis of Java island. After the formation of ancient volcanic mountain ranges as a volcanic belt, from the late Oligocene to early Miocene there was a series of tremendous volcanic events. This is evidenced by the numerous discoveries of pyroclastic outcrops and volcanic sediments. From these outcrops at least 2 ancient volcanic products are identified, namely Semilir and Nglanggeran.

Subsequently there was cooling and sedimentation in the late Pliocene. And later, the conducive geological conditions made Java a habitat for pre-hominids whose fossils were discovered by researchers in the Dutch East Indies era.

Pithecanthropus Erectus was discovered by Eugene Dubois in 1891 in Trinil, Ngawi, East Java. Pithecanthropus Erectus is estimated to have lived around 700,000 to one million years ago based on the middle Pleistocene layer at the fossil discovery site.

The name Pithecanthropus erectus was later assigned because the fossils discovered formed a human skeleton resembling an ape. The word Pithecanthropus erectus comes from Greek, phithkos meaning ape, anthropus meaning human, and erectus meaning upright.

While the definition of Indonesian humans from a genomic perspective and their migration processes is explained by Prof. Herawati Sudojo in her scientific oration at the 2018 Dexa Award Science Scholarship entitled Diverse Genes, One Indonesia which is the result of mixing that occurred during the repeated process of journeys and movements.

In their journey to become Indonesian humans, genetically there are four waves of migration that contributed. The early wave, the ancestors of Indonesians arrived 50,000 years ago via the southern route to the Sunda Shelf which at that time still combined the islands of Kalimantan, Sumatra and the Malay Peninsula.

Meanwhile, the history of modern humans (Homo sapiens) itself began from the African continent about 150,000 years ago. 30,000 years later, a group of humans traveled north through Egypt and Israel. However, their traces disappeared.

Another group, about 72,000 years ago, moved to the southern part of the Arabian Peninsula towards India. Then 40,000 years ago there were two migration events. There was a group that moved north from Pakistan through the Indus River and moved to the Bering Strait. These were the inhabitants of the Americas continent approximately 15,000 years ago. They are much younger than the inhabitants of the Indonesian archipelago.

Based on samples of mitochondrial DNA markers which are only passed down the maternal line, it is known that the initial habitation period in the Indonesian archipelago ranged between 70,000–50,000 years ago. Meanwhile, analysis of Y chromosome markers which are only inherited from the paternal line shows evidence of blending of several genetic ancestors.

From the results of mitochondrial DNA and Y chromosome examinations, it was also found that populations in the archipelago have genetic traces of early Out of Africa human migration waves that went along the southern route around 60,000 years ago.

From tracing those genetic footprints, it is also known that our ancestors originating from East Africa went north spreading through the Nile River valley, Sinai Peninsula or through the Red Sea to Saudi Arabia southward, passing through Indonesia to Australia.

While Austronesian speakers entered the regions of Kalimantan and Sulawesi from mainland China, Taiwan, and the Philippines around 4000 years ago. While Astro-Asiatic speakers from Asia entered earlier through the Sundaland plains in Sumatra, Java and Kalimantan.

There is a possibility as in Oppenheimer’s out of Sundaland theory, that culture and civilization in Asia and Europe were part of a return migration process of Homo sapiens from the archipelago.

This is relevant when associated with various new facts related to the discovery of archaeological sites such as Gunung Padang which is more than 10,000 years old.

Going back to Sundaland, from data compiled on the studigeologi website/blog, it is known to have a geological age with a relatively long time range in a quite unique stratigraphic approach.

Geology recognizes the division of time, where geological time is divided into four eons: Hadean, Archean, Proterozoic, and Phanerozoic. The Phanerozoic is further divided into three main eras: Paleozoic, Mesozoic, and Cenozoic.

Each era is then divided into periods, and each period consists of epochs. For example, the Mesozoic era includes the Triassic, Jurassic and Cretaceous periods. Periods are then divided into epochs, but this division can vary depending on the region and type of rocks observed.

This concept helps earth scientists understand the geological history of the earth and understand the evolution of life as well as changes in climate and environment.

The following is the division of time and geological time range in estimated years based on observations of rock structures, tectonic evolution, and the existence of living things.

1. Eon:

• Hadean: 4.6 billion years ago to 4 billion years ago.
• Archean: 4 billion years ago to 2.5 billion years ago.
• Proterozoic: 2.5 billion years ago to 541 million years ago.
• Phanerozoic: 541 million years ago to present.

1. Era:

• Paleozoic: 541 million years ago to 252 million years ago.
• Mesozoic: 252 million years ago to 66 million years ago.
• Cenozoic: 66 million years ago to present.

1. Period: (example in Mesozoic)

• Mesozoic:
• Triassic: 252 million years ago to 201 million years ago.
• Jurassic: 201 million years ago to 145 million years ago.
• Cretaceous: 145 million years ago to 66 million years ago.

1. Epoch:

• Epoch time ranges can be more varied, often in millions of years, and can differ depending on literature or region.

The tectonic history of Sundaland according to Hutchinson (1973) can be divided into several parts, starting from the Carboniferous-Permian period.

In the Carboniferous period, where the Carboniferous period is the fifth interval of the Paleozoic Era succeeding the Devonian Period and preceding the Permian Period starting around 358.9 million years ago and ending 298.9 million years ago with a duration of around 60 million years making it the longest period of the Paleozoic Era and the second longest period of the Phanerozoic Eon,

subduction activity occurred west of Sumatra producing volcanic and pyroclastic rocks with compositions ranging from dacite to andesite in the area stretching across the Padang Highlands, Batang Sangir and Jambi (Klompe et all., 1961; in Hutchison, 1973). Granitic intrusive rocks formed on the Malay Peninsula, across Penang Island, and are estimated to continue to the Riau Islands.

In the Permian period, there was no change in the distribution of plutonic and volcanic rocks from the Late Carboniferous. The trench-arc system operating in Sumatra still did not change. Andesitic to rhyolitic volcanic and pyroclastic rocks spread in the western part of Central Sumatra.

From the Late Triassic to Early Jurassic, subduction in Sumatra continued and produced the Aceh ophiolite complex in the north and the Gumai-Garba ophiolite complex in the south. According to Bemmelen (1949; in Hutchison, 1973) the two ophiolites are Triassic in age.

In the Middle Jurassic to Middle Cretaceous, there was uplift in the Malay Peninsula region, causing changes in sedimentation environments in the area from marine to terrestrial, marked by molasse type deposits and fluvial sedimentation. Volcanism in the Sumatra region and surroundings was less active during this timeframe. During the Jurassic and Cretaceous, the Sumatra region and surroundings were cratonized, and strike-slip fault systems formed (Tjia et al., 1973; in Hutchison, 1973). This strike-slip fault was due to the collision of the Indian plate with Eurasia.

In the Late Cretaceous, the subduction zone moved west of Sumatra, along the islands currently west of Sumatra such as Siberut. The ophiolites from this subduction were estimated by Bemmelen (1949; in Hutchison, 1973) to be Late Cretaceous to Early Tertiary in age.

In northern Sumatra there are Tertiary granitic intrusions while in the south there are Older Andesites and Early Miocene Granite Intrusions. The pattern of the trench-arc system in Sumatra at that time was first depicted by Katilli (1971; in Hutchison, 1973) as in figure 5. The subduction west of Sumatra continues south to West Java, then turns northeast towards the Meratus Mountains in East Kalimantan.

In the Late Jurassic the Banda Block which was previously attached to Gondwana separated and moved away from the Sula Spur. The Argo Block then separated subsequently through a spreading process.

The spreading developed westward continuing to the margin of Greater India 2. Island arcs and continental fragments moved away from Gondwana as a result of rollback from subduction.

In the Early Cretaceous

around 135 million years ago, India began to separate from Australia and Papua which were still attached to Antarctica. The spreading at the Ceno Tethys had an average NW-SE orientation. The Argo Block and Woyla Arc moved towards Southeast Asia.

About 25 million years later India separated from Australia. The Argo Block approached Sundaland and the NW-SE spreading at Ceno-Tethys stopped. The spreading center between India-Australia developed northward. Subduction occurred in southern Sumatra and southeast Kalimantan.

90 million years ago the Argo Block approached northwest Kalimantan and the Woyla Arc approached the edge of Sumatra. These collisions caused the previously ongoing subduction to stop. India continued to move northward through subduction at the Incertus Arc. Australia and Papua began to slowly drift away from Antarctica.

In the Late Cretaceous, India moved rapidly northward due to fast spreading in the southern part and transform faults formed. There was no significant movement between Australia and Sundaland and no subduction occurred below the islands of Sumatra and Java.

Around 55 million years ago (Early Eocene), the Australia-Sundaland movement caused subduction along the western edge of Sundaland, below Sumba Island and West Sulawesi, and possibly continuing northward. The boundary between the Australia-Sundaland plates in the southern Java was a strike-slip zone while in southern Sumatra it was a transtensional strike-slip zone. The Incertus Arc and northern boundary of Greater India collided and continued to move northward.

Around 45 million years ago (Middle Miocene), Australia and Papua began to drift rapidly away from Antarctica. Basins formed around the Celebes and Philippines areas and a southward subduction zone in the proto South China Sea area. Around 35 million years ago, the Sundaland area began to rotate counterclockwise, with the eastern part of Kalimantan and Java relatively moving northward. This rotation occurred due to the interaction between the Indian plate to Asia.

Around 15 million years ago (Middle Miocene), the older portion of the oceanic crust on the Banda Block which was older than 120 million years reached the subduction zone south of Java. The trench developed eastward along the plate boundary to the southern part of the Sula Spur. Australia and Papua approached their present position and arms of Sulawesi began to collide. (Studigeologi Blog)

In the Holocene period formed the Indonesian archipelago as we know it today. During this period grew and developed various cycles of civilization marked by the existence of cultural heritage from the era of Kutai Kartanegara, Tarumanagara (Candrabaga and Gomati canals), Medang/Mataram Kuno, Srivijaya, Galuh, Sunda, and Majapahit.

After that began the era of globalization marked by the prevalence of migration processes as described by Dennys Lombard in his book Nusa Jawa Silang Budaya. World cultures entered Indonesia and became part of the diversity of civilizations that color us today.

Behind all that there are still lingering questions and also millions of hypotheses about Sundaland whose natural conditions resemble what is described in Plato’s Timaeus and Critias, a heavenly plain with biodiversity that gave birth to highly civilized humans.

The remaining question is, “can we go back to being grateful for the gifts that we still inhabit today, so that we can reach the highest civilization again?” Of course this is a big homework for all of us.