The Lesser Sundas Part 2: Timor and the Remaining Isles
Introduction
The treasure trove of fossils at Liang Bua paint a compelling ecosystem present in Flores and Sumba consisting of everything from giant storks to tiny hominids, all of which was discussed in part 1. Liang Bua has very effectively drawn up an approximation of when the megafauna of Flores disappeared and provides by far the clearest indication of extinction timing in the Lesser Sundas. In this article we turn to Timor – the easternmost of the major islands that make up the Lesser Sundas. Its location places it much closer to the Sahul landmass than Sundaland – during times of low sea-levels only being divided by the narrow Timor strait. The island boasts a sizable fossil record of its own, which although similar to that of Flores, has notable differences in fauna and suffers from poor dating. More importantly, Timor yields the best record of Pleistocene archaeological evidence from the Lesser Sundas and places the arrival date of Homo sapiens to the archipelago on a much surer footing.
We shall discuss the present evidence from Timor, including its extinct fauna, archaeological records and climatic data and briefly cover the limited evidence present from the remaining isles. This culminates in an evaluation of the state of evidence for the megafauna extinctions in the Lesser Sundas as a whole.
Figure 1. Map of Timor in the Lesser Sundas, along with sites mentioned in the text.
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The Faunal Overview
The faunal composition of Timor is similar to that of Flores, but with endemic species and notable omissions. Timor appears to have possessed a species of monitor lizard which eclipsed the Komodo Dragon in size, it would undoubtedly have constituted the apex predator of the island. The species is known solely from a few vertebrae remains and therefore lacks a formal description and scientific name, for simplicity we shall refer to it as the Timor dragon (7, 8). Despite the prevalence of Varanus komodoensis in Flores and Sumba to the West and Sahul to the East (7), it appears the Timor dragon’s vertebrates were more akin to those of Megalania (Varanus priscus) from Sahul (7)(8). Nevertheless, more material will be needed to erect it as a distinct species. Material from Australia similar to the Timor Dragon may indicate that it was once a wide-ranging species (7). On Timor, the dragon was found only at a single site called Atambua which is Middle Pleistocene in age (7, 8) and not well studied, thus figuring out when the species went extinct is impossible with current evidence. As with Flores-Sumba, Timor is home to a native small monitor lizard, the spotted tree monitor (Varanus timorensis), but in this case the species is still common throughout Timor and subsists primarily on invertebrates and small vertebrates (2).
Figure 2. Spotted Tree Monitor (Varanus timorensis) is the only native species of monitor lizard on the island of Timor and is endemic to Timor and small neighbouring isles.
Terms of use: This image is licensed under a creative commons attribution-ShareAlike 3.0 Unported. It is attributed Mark O’Shea. The image is unedited and the original can be found here
A species of giant tortoise also inhabited Timor during the Pleistocene (17), this species was assigned to Geochelone atlas, a giant tortoise described from the early Pleistocene of India (9), since redubbed Megalochelys siwalik. However, the Timor giant tortoise likely constitutes a distinct species of Megalochelys closely related to M. siwalik and the giant tortoises of Flores, Sumba, and Java (18). As with the Timor dragon, the remains of the Timor giant tortoises are from poorly studied sites from the middle Pleistocene, with no accurate dating conducted (17). There is also fossil evidence of an undescribed crocodile of the genus Crocodylus, possibly ascribable to the Siamese crocodile (Crocodylus siamensis), but likely a distinct species (9).
Timor had its own proboscidean as well – Stegodon timorensis – a species slightly larger than S. sondaari of Flores (Estimated at 490kg). A tusk from S. timorensis discovered from Atambua has been directly dated to 130kya (12), with two additional Stegodon fossils from the Middle Pleistocene demonstrating ages of 670kya and 710kya (10), but the temporal range of the species remains poorly resolved. Specimens from a larger and rarer species of Stegodon are also known from Timor, but their taxonomic identity and age is currently unclear (12). It is possible that these two Stegodonts of different sizes follow the pattern seen on Flores, where a larger species is found in earlier deposits but decreases in size over time.
Figure 3. Timor dragons flocking around their kill, a Stegodon timorensis on a grassy hillside on Timor during the Late Pleistocene. The remaining herd looks on from afar. Artwork commissioned for The Extinctions by Hodari Nundu.
An avian assemblage from Laili cave in Timor-Leste comprised at least 9 different species – though most could only be narrowed to family or genus level, and none yielded any extinct taxa (4). This was further added to by Meijer et al 2019, most notably finding two taxa not currently present on Timor – A crane (Grus sp.) and large buttonquail (Turnix sp.), both are speculated to belong to extinct species, though further material is needed to confirm this (14). It is worth noting that at present no equivalent of Leptoptilus robustus or Trigonops sp. have been found on Timor.
As is the case for Flores, Timor hosts its own distinct community of endemic rats. Of these only one is extant today, the Timor rat (Rattus timorensis) (1). A wealth of extinct murids populated the island with at least seven species of giant rat (1, 11), the largest of which reached a staggering 5kg and holds the record of the biggest known species of rat (11). Five of the extinct murid species remain undescribed including the largest species, but two have been dubbed Coryphomys buehleri and Coryphomys musseri respectively (1).
Interestingly, Timor lacks any evidence of pre-Homo sapiens hominids. Though it can’t be ruled out that the island might have supported an as of yet undiscovered species, it is more likely that Flores supported the easternmost hominid occurrence in Wallacea, and that Timor remained completely naive to hominids until the arrival of modern man.
Fossil records are lacking altogether in Lombok and Sumbawa, which during much of the Pleistocene were connected (5). One can only make educated guesses at what might have inhabited those islands based on the regional biogeography. Giant species of Varanus and dwarf Stegodon were present on Sumba, Flores, Timor, and Java (7) and this almost certainly was also true of Lombok and Sumbawa. Crocodiles and giant tortoises also seem to have been ubiquitous in the Lesser Sundas. As the two western-most islands in the Lesser Sundas the fauna of Lombok and Sumbawa probably resembled Flores more than Timor, and it is interesting to contemplate whether they boasted their own equivalents of Homo floresiensis. Perhaps their proximity to Java allowed colonization of additional species that never made it as far as Flores? If so, they may well be the most species-rich of the Lesser Sundas. Until palaeontological remains are discovered we can only speculate.
Additional fossil evidence can be found from a few of the small islands in the Lesser Sundas, most notably Alor and Kisar which are located to the north of Timor. These remains clearly post-date the megafauna extinctions in the region and will not be pertinent to the overall discussion, but the islands do hold a few discoveries, nonetheless. Alor has yielded its own distinct genus and species of giant rat, dubbed Alormys aplini (13). Two (presumably) extinct species of rats have also been retrieved from Kisar, one large and one giant, though neither species has received a formal description (16).
The Issue of Dating
Investigating extinctions on Timor is more difficult than on Flores due to poor stratigraphy during the relevant portions of the Late Pleistocene. The vast majority of megafauna remains come from Atambua, which dates primarily to the Middle Pleistocene. Consequently, the few remains that have been dated are old, and have the additional issue of belonging solely to Stegodon. The youngest remains are dated to about 130kya (12), yet given the scarcity of fossil remains we can’t use this final occurrence to estimate the extinction date, that is because of the Signor-Lipps effect. Consider a species which lasted for a million years and randomly sample one of its fossils, how likely is it you found a fossil in the last 100 thousand years of that species’ existence? Assuming equal rates of fossilization and population sizes, 10%. Even if you found three fossils the probability would only be 27%. And so it is with the Stegodon remains on Timor, the true extinction date is very likely to be after 130kya, though how much later is impossible to say for sure. Unfortunately, the main fossil-bearing site – Atambua – also lacks the well-defined and dated stratigraphy of Liang Bua in Flores making it difficult to establish a sequence of events and extinctions.
Looking then to the archaeological evidence, unlike on Flores, we have unequivocal evidence of Homo sapiens occupying Timor during the Pleistocene. In fact, the island contains the oldest confirmed remains of Homo sapiens in the Lesser Sundas. The evidence of an early human arrival on Timor can be found at three separate sites: Jerimalai, Lene Hara and Lailli Cave. Jarimalai was the first to be dated in 2007 and is estimated to have remains associated with humans from about 42kya (15). Evidence is restricted to simple stone tools, which cannot be confidently ascribed to any particular species of hominid, however most likely belonged to Homo sapiens as this designation is in line with human arrival elsewhere in the region and a primary use of marine resources (15). Earliest evidence of Homo sapiens occurrence at Lene Hara is contemporary with that of Jerimalai, with earliest remains also dating to about 42kya and consisting of animal bones, shells and stone artefacts, assumed to belong to Homo sapiens. Turning finally to Lailli Cave, stone tools likewise turn up here along with fragmented human remains with the earliest archaeological remains dating to about around 44-45kya.
Figure 4. Cave paintings from Lene Hara. The painting dates to the Holocene, with older carvings dating back almost 30 thousand years (20).
Terms of use: This image is licensed under a creative commons attribution-ShareAlike 3.0 Unported. It is attributed David Palazon. The image is unedited and the original can be found here
This places a tentative date of latest possible colonization of the Lesser Sundas by modern humans at around 45kya. There are reasons to imagine this date goes back slightly further. Firstly, there are remains from slightly deeper layers of Lailli cave that may predate 45kya but could not be dated directly. Additionally, the Lesser Sundas may have acted as stepping stones in the dispersal of Homo sapiens between Sundaland and Sahul. The exact arrival date of Homo sapiens in Sahul is still a controversial topic, recent finds from Northern Australia have suggested a date as early as 65kya (19), but this timing remains disputed, and more conservative studies suggest a more modest 50kya arrival date (16). Regardless, the Lesser Sundas is one of two proposed pathways for humans to have dispersed from Sundaland to Sahul, this is commonly called the Southern route. The alternative northern route runs through Sulawesi and the Moluccas. Neither the colonization date of Sahul, nor an evaluation of the most likely pathway to the continent are within the scope of this article, other than to say that the colonization of the Lesser Sundas has the potential to reach back further in time than demonstrated dated remains.
At Lailli Cave, an abundance of invertebrate and vertebrate have been found in association with the site, but there is a conspicuous absence of any megafauna (3, 4). This implies that the megafauna extinctions occurred prior to the founding of the settlement. Supposing that megafauna extinctions occurred before the dated remains at Lailli around and after the latest dated Stegodon bone, this leaves a possible extinction window of between 130kya and 45kya. That is the current temporal resolution possible from the state of evidence from Timor alone.
Given the similarity in the fauna of Timor and Flores, their proximity to one another, and the fact that both islands saw a collapse of their megafauna at some point in the Late Pleistocene, it is very reasonable to suggest that the underlying cause was the same. Two independent megafaunal collapses so close in time and space would be quite extraordinary. If the extinctions in the Lesser Sundas are connected, the Timor megafauna probably died out around 50-47kya as in Flores, though future studies will be needed to disprove or corroborate such a supposition. It should be noted that, as on Flores, the extinct rats of Timor, Alor and Kisar seem to have survived far longer than the megafauna (3, 13, 16).
Figure 5. Timeline of key events at Timor, green denoting periods with megafauna present, yellow denoting units not bearing dated fossils and red lacking megafauna.
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Extinction in the Lesser Sundas
The underlying cause of the extinction of the megafauna of Timor is difficult to evaluate conclusively, due to a scarcity of evidence, but human- and climate-caused extinctions remain by far the most popular explanations.
Assuming that megafauna extinctions in Flores and Timor are roughly synchronous and that Homo sapiens colonised Flores shortly before, or after, they colonised Timor. This would put the earliest evidence of human arrival in the Lesser Sundas within spitting distance of the disappearance of its megafauna – rendering it a compelling hypothesis. There is no direct evidence of human hunting of megafauna in the Lesser Sundas. Even supposing a human-driven extinction, this is unsurprising. It is difficult to evaluate how long it would take for Homo sapiens to eradicate the Lesser Sundas megafauna under an overkill hypothesis, however the stratigraphy from Liang Buas well-studied layers suggests there may have been at most a few thousand years overlap, and perhaps less. Given that the amount of fossil evidence from the Lesser Sundas is limited and localised in time, the vast majority of remains likely predate human arrival. Evidence of human hunting would truly be a lucky discovery. A human-driven cause therefore presents a plausible hypothesis, but one lacking direct evidence outside of a temporal correlation.
How then does a climatic hypothesis hold up in comparison? There’s unfortunately very little data from Timor to go on. The primary studies investigating this subject matter come from the archaeological periods, that is, presumably after the megafauna extinctions have occurred. At Lailli Cave, the oxygen and carbon isotopic data from local gastropods suggests that despite major changes in sea levels during the Late Pleistocene, the conditions were relatively stable from 44,000 years and until the onset of the Holocene (3). This however tells us very little about the local conditions in the period 130kya to 45kya, which would be of interest in evaluating a climate-based hypothesis. In the same vein, Hidayah et al 2021 investigated the palaeoenvironment of Timor and its change over time based on pollen evidence from the Atambua Basin, but these records cover only the Middle Pleistocene well prior to the extinction of the megafauna. As discussed in part 1, current evidence from Flores indicates that there is no evident connection between the megafaunal collapse and climate change. Thus, as of the 2024, there’s an absence of any local data supporting a major climatic shift in conjunction with the demise of the Lesser Sundas megafauna and additional studies will be needed to verify any hypothesised connection.
The giant rats of Timor and elsewhere seem to survive the original colonization of the island by Homo sapiens and last well into the Holocene (11), it has been proposed that their extinction may be in line with habitat loss due to deforestation during the Late Holocene by indigenous tribes. Interestingly, this is despite evidence of prolonged and extensive hunting, as observed by large abundances of cut and burnt bones during the Pleistocene (11). The small size (relative to megafauna) and likely fast reproduction rates of the endemic rats seem to have been sufficient to maintain their populations in the face of hunting pressure. Inferences regarding the Timor crane are difficult to make as it is known only from a single Late Pleistocene specimen, however the large buttonquail is known from a range of deposits, with the terminal records coinciding roughly concurrently with the disappearance of the giant rats (14).
On the whole, human-caused extinction presents the most persuasive explanation for the megafaunal collapse in the Lesser Sundas during the Late Pleistocene. Liang Buas stratigraphy provides the most compelling evidence with megafauna remains immediately prior to the appearance of more complex stone tools. This coupled with the dating of concrete human remains from Timor around the same time point in time, point towards a relationship between the arrival of Homo sapiens and the disappearance of the Lesser Sundas megafauna. In contrast a climatic explanation of extinction in the region lacks any clear evidence of correlation, let alone causation. Existing data from Flores suggests that climatic shifts occurred prior to, and well after the disappearance of megafauna from the archipelago.
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