**4. Conclusions**

1.Prefigured by many geographic properties, bathymetric barrier presents to appear as the strongest casual effect in enforcing island isolation in Southeast

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*Mainland versus Island Adaptation: Paleobiogeography of Sunda Shelf Primates Revisited*

disconnect more to the original continental population.

from mainland than continental islands.

(e.g., Flores Island).

ated in such condition.

varied living *Presbytis* species in Borneo Island.

Asian Archipelago, expressed by the high degree of endemism in level of species in oceanic islands (i.e., *Homo floresiensis* in Flores Island and six non-human primates in Mentawai Islands). Vicariance geography in any form of barriers (e.g., mountain and river) could create allopatric speciation or endemism; however bathymetric barrier on island extraordinarily emerged in different process. The higher sea depth caused the higher chance for island population to

2.The duration of island isolation widens to promote the evolutionary results that yield the island ecological mechanism becoming intensified. The higher time cost on ecological factors such as selective pressures and predator avoidance could escalate the chance for anatomical feature to be modified. Although it is hard to know the absolute duration of island isolation, the relative isolation can be seen from the present bathymetry showing the predicted terminal time for body of water to cover the maximum depth that stop the connection from mainland to surrounding islands. Constituted by this concept, oceanic islands with high bathymetric barrier will definitely prolong the disconnection signal

3.When we control geographical and chronological isolation factors, the two main island ecosystem factors, faunal association and vegetation type, strongly contribute to the change of body size and shape, resulting in a higher island effect. Patterns impacted by this ecosystem factors are not the same in all islands. The imbalanced condition on fauna between the number of herbivores and carnivores and less interspecific faunal diversity could lead to the body size shift and anatomical modification. On primates, oceanic islands located near the equator covered with the densely tropical rain forest gave less likely island effect (e.g., Mentawai Island and Simeulue Island) than in oceanic island with drier and more open environment where resource is less abundantly available

4.Latitudinal factor is clear to be seen in the mainland. While each island holds unique geographical properties directing to isolation (e.g., bathymetric barrier and island size), most Southeast Asian islands that are located around the equator with tropical weather resulting in major rain forest cover and short latitudinal range rather rise to contribute to more diverse body size and body shape longitudinally. Thus, Bergmann's rule is seemingly irrelevant to be evalu-

5.The primates of Sunda Shelf occupying the great number of islands scattered in large scale area did not perform any pattern in regard to correlation between body size and island size. Potential causal relation to island size is more manifested in the increasing taxonomic diversity. Large-sized islands throughout Sunda Shelf hold higher diversity in anatomical variation than in small-sized island. It is supposedly due to the combination of possible isolation-derived process by geographic or ecological barrier and the resiliency of relict species along many stages of period. This circumstance is conceivably reassured from the Quaternary through recent, for example, the high diversity of calvarium morphology seen in *Homo erectus* of Java Island and the occurrence of four

6.Endemism featured on non-human primates in continental islands of Sunda Shelf mostly direct to the resilience of relict groups occupying the island, not

*DOI: http://dx.doi.org/10.5772/intechopen.90051*

*Mainland versus Island Adaptation: Paleobiogeography of Sunda Shelf Primates Revisited DOI: http://dx.doi.org/10.5772/intechopen.90051*

Asian Archipelago, expressed by the high degree of endemism in level of species in oceanic islands (i.e., *Homo floresiensis* in Flores Island and six non-human primates in Mentawai Islands). Vicariance geography in any form of barriers (e.g., mountain and river) could create allopatric speciation or endemism; however bathymetric barrier on island extraordinarily emerged in different process. The higher sea depth caused the higher chance for island population to disconnect more to the original continental population.


*Pleistocene Archaeology - Migration, Technology, and Adaptation*

**3.3 Ecological cost: fauna association and vegetation**

*3.3.1 Fauna association*

*3.3.2 Vegetation*

scenario passing deep sea barrier to reach oceanic islands of Lesser Sunda presumably occurred by human transport during <4.5 ka [5], because swimming is not possible due to the strong sea current in Lombok Strait. This data is supported by the presence of *M. fascicularis* remains in archeological cave aged ca. 7 ka in Timor Island [5, 27].

With limited connection to the diverse mainland fauna, isolated island promotes the poor taxonomic diversity and the imbalanced rate between herbivores and carnivores. Small island has been claimed to reduce the sympatric speciation than large island [31]. This condition drove a disharmonic inter- and intraspecific variation [12]. For instance, in severe ecological condition when food resources are limited in long duration, the large-bodied species tends to expand their territory where small-bodied species fails to compete and being enforced to undergo stronger dietary adaptation. This response to ecological condition led to a radiation into different size classes and morphotypes, which arrives to appear in the form such as anatomical modification (e.g., dental pattern, size, and shape of limb bone) causing genetic radiation [12]. In most case, this disharmonic taxonomic diversity condition dropped the survivability. The heavily impoverished condition leads to some species to extinction, for example, in all Late Pliocene-Early Pleistocene (*Sinomastodon-Megalochelys* stage) species in Java and large- to intermediate-bodied fauna in Flores Island in Late Pleistocene. It is followed by imbalanced condition where the normal ratio between carnivores and herbivores is high. Predator avoidance is suggested to cause the limb bone modification. A species that is not threatened by the carnivores might

not often walk and run leading to the less development of limb bones.

on cercopithecids assemblage in Punan Vuhang, Sarawak, Borneo [52].

1.Prefigured by many geographic properties, bathymetric barrier presents to appear as the strongest casual effect in enforcing island isolation in Southeast

The vegetation type of an area derives from mean temperature caused from latitudinal position, geographical topography, seasonality by monsoon, and geological sediments. During Quaternary, the fluctuating temperature prominently contributes to habitat changes. The ecological shift from tropical rainforest to more open environment in Early-Mid Holocene resulted in biodiversity loss in non-human primates; for example, it is shown by the disappearance of *Presbytis comata* (Javan langur) in eastern Java that was previously found in Braholo Cave, East Java (Late Pleistocene to Mid Holocene) [45], and the extinction of Pongo in Java that was formerly discovered in Punung rockshelter, East Java (Late Pleistocene) [46–48]. This open environment niches created the mosaic ecological niche in eastern Java [45, 49] that enforced the early *Homo sapiens* inhabiting Java to hunt the remaining arboreal fauna including non-human primates as food resources. Archeological evidence depicting *Homo sapiens* that consumed monkeys (*Macaca*, *Presbytis*, and *Trachypithecus*) are also discovered in Song Terus cave in the period from 9000 to 5000 years ago [50] and Niah Cave, Borneo [51]. Further ethnographic account resembling this phenomenon is found as butchery marks and burnt bone fragments

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**4. Conclusions**

necessarily in response to a long-term island isolation process. In the level of species, this premise is endorsed by the existence of a single taxon occupying large islands (e.g., *P. abelii* in Sumatra, *P. pygmaeus* in Borneo, *H. moloch* in Java). Smaller continental islands bordered by relatively higher bathymetric barrier could possibly produce the isolation-derived endemism process in the level of subspecies (e.g., *M. f. baweanus* in Bawean Island and *M. f. karimoendjawae* in Karimun Jawa Island).
