Environmental drivers of megafauna and hominin extinction in Southeast Asia

Abstract

Southeast Asia has emerged as an important region for understanding hominin and mammalian migrations and extinctions. High-profile discoveries show Southeast Asia was home to at least five members of the genus Homo 1-3 . Significant turnover in Pleistocene megafauna is linked with these hominins or climate change 4 , although the region is often left out of discussions of megafauna extinctions. Establishing the environmental context of hominin evolution and its association with faunal changes have long been informed by stable isotope methodologies in the traditional evolutionary core of Africa 5,6 . However, such studies have been largely neglected in Southeast Asia.Here, we present the first large-scale dataset of stable isotope data for Southeast Asian mammals spanning the Quaternary. Our results demonstrate that Early Pleistocene forests gave way to savannahs by the Middle Pleistocene leading to the spread of grazers and extinction of browsers, although geochronological limitations mean that not all samples can be resolved to glacial/interglacial periods. Savannahs retreated by the Late Pleistocene and completely disappeared by the Holocene, replaced by highly stratified closed canopy rainforest. This resulted in the ascendency of rainforest-adapted species, including our own, at the expense of savannah and woodland specialists, such as Homo erectus. Megafauna today are restricted to rainforests and severely threatened by anthropogenic deforestation.

A multi-proxy approach to exploring Homo sapiens’ arrival, environments and adaptations in Southeast Asia

“…S7 ). They are consistent with the environmental reconstruction made by Louys and Roberts 11 . Our findings also question the relationship between the changes in the rainforest environment and the major turnover of earlier hominins ( H. erectus , Denisovans) in SE Asia before the arrival of H. sapiens.…”

“…During the Late Pleistocene, the Far East witnessed a major turnover of hominins with the extinction of the last H. erectus in Indonesia 8 , the likely presence of the last Denisovans in several parts of the continent 9 and eventually the replacement of all archaic groups following the arrival of Homo sapiens 10 . On a continental scale, it has been suggested that the shift from open habitats (mixed savannah and woodland) to rainforest habitats at the transition between the Middle Pleistocene and the Late Pleistocene triggered the decline of archaic hominins, unable to adapt to these new environments 11 .…”

“…1 ). From a palaeoecological point of view, the crown dimensions and stable isotopic measurements of identified taxa from these faunas are proxies for environmental reconstruction 7 , 11 , 20 , 22 – 24 and a primary source of information on biotas occupied by hominins. In the area studied, the earliest occurrence of H. sapiens is documented by skeletal remains of several individuals from ~ 70 ka at Tam Pà Ling (~ 70–46 ka 25 , 26 ) and by two teeth at Duoi U’Oi (70–60 ka 22 ).…”

Different environmental variables predict body and brain size evolution in Homo

“…As such, our findings can be related to changes in subsistence strategies toward more frequent and systematic hunting of larger-sized bovids in these environments, in association with cognitive changes toward more complex weapons and coordinated group activity. The lithic, faunal, and isotopic records show an increase of such behaviors and ecosystems inhabited by Homo throughout the Middle Pleistocene that supports this interpretation [40][41][42][43] . The divergent pattern in Neanderthals and Pleistocene H. sapiens might be due to an already higher established brain size close to the physiological maximum during colonization of more northern latitudes (>40°; H. sapiens: mean = 1505 cm 3 , n = 37; Neanderthals: mean = 1398 cm 3 ; n = 25), while the other taxon either evolved in situ in these areas or had higher growth potential.…”

Red Panda feces from Eastern Himalaya as a modern analogue for palaeodietary and palaeoecological analyses

“…The underlying causes for the megafaunal extinction at the end of the Pleistocene are still debated and tend to focus on two primary issues, climatic/environmental change and anthropogenic activities, or some combination of these 3 – 7 . The current rate of population reduction and potential extinction of herbivores and carnivores in the wild is a major global ecological issue.…”