Early research The name "Sunda" goes back to antiquity, appearing in
Ptolemy's
Geography, written around 150 AD. In an 1852 publication, English navigator
George Windsor Earl advanced the idea of a "Great Asiatic Bank", based in part on common features of mammals found in Java, Borneo and Sumatra. Explorers and scientists began measuring and mapping the seas of Southeast Asia in the 1870s, primarily using
depth sounding. In 1921
Gustaaf Molengraaff, a Dutch geologist, postulated that the nearly uniform sea depths of the shelf indicated an ancient
peneplain that was the result of repeated flooding events as ice caps melted, with the peneplain becoming more perfect with each successive flooding event. and described in greater detail by Emmel and Curray in 1982 complete with
river deltas,
floodplains and backswamps.
Data types The climate and ecology of Sundaland throughout the Quaternary has been investigated by analyzing
foraminiferal
δ18O and pollen from cores drilled into the ocean bed,
δ18O in
speleothems from caves, and
δ13C and
δ15N in bat guano from caves, as well as species distribution models, phylogenetic analysis, and community structure and species richness analysis.
Climate Perhumid climate has existed in Sundaland since the early
Miocene; though there is evidence for several periods of drier conditions, a perhumid core persisted in Borneo. Most recent research agrees that Indo-Pacific
sea surface temperatures were at most 2-3 °C lower during the
Last Glacial Maximum. However, debate continues on how precipitation regimes changed throughout the Quaternary. Some authors argue that rainfall decreased with the area of ocean available for evaporation as sea levels fell with ice sheet expansion. and an increase in land area in the Sunda Shelf alone (due to lowered sea level) is not enough to decrease precipitation in the region. Alternatively, the physical and chemical processes that underlie the method of inferring precipitation from
δ18O records may have operated differently in the past.
Savanna corridor theory Dipterocarp trees characteristic of modern Southeast Asian tropical rainforest have been present in Sundaland since before the
Last Glacial Maximum. There is also evidence for
savanna vegetation, particularly in now submerged areas of Sundaland, throughout the
last glacial period. However, researchers disagree on the spatial extent of savanna that was present in Sundaland. There are two opposing theories about the vegetation of Sundaland, particularly during the last glacial period: (1) that there was a continuous savanna corridor connecting modern mainland Asia to the islands of Java and Borneo, and (2) that the vegetation of Sundaland was instead dominated by tropical rainforest, with only small, discontinuous patches of savanna vegetation. Morley and Flenley (1987) and Heaney (1991) were the first to postulate the existence of a continuous corridor of savanna vegetation through the center of Sundaland (from the modern Malay Peninsula to Borneo) during the
last glacial period, based on palynological evidence. In contrast, other authors argue that Sundaland was primarily covered by tropical rainforest. Soil type, rather than long-term existence of a savanna corridor, has also been posited as an explanation for species distribution differences within Sundaland; Slik et al. (2011) suggest that the sandy soils of the now submerged seabed are a more likely dispersal barrier.
Paleofauna Before Sundaland emerged during the late Pliocene and early Pleistocene (~2.4 million years ago), there were no mammals on Java. As sea level lowered, species such as the dwarf elephantoid
Sinomastodon bumiajuensis colonized Sundaland from mainland Asia. Later fauna included tigers, Sumatran rhinoceros, and Indian elephant, which were found throughout Sundaland; smaller animals were also able to disperse across the region. ==Human migrations==