To explore the paleoenvironmental changes in SE Asia during the late Neogene, we examined the stable carbon and oxygen isotope compositions of tooth enamel from mammals of the late Pliocene/earliest Pleistocene Gwebin area in central Myanmar and compared the results with those of the latest Miocene Chaingzauk mammals in Myanmar. The stable carbon isotope values (δ¹³C) of Gwebin mammals indicate that they inhabited mosaic environment ranging from woodland to grassland. The relative abundance of C₃-browsing versus C₄-grazing bovids as well as other C₃-consuming anthracotheriids, porcupine, rhinoceroses, suids, and stegodontids suggest the dominance of wooded environment. In central Myanmar, it is assumed that floral transition from C₃ to C₄ plants has occurred since the latest Miocene to Early Pliocene relating to the Himalayan Orogeny. However, stable isotope data at present indicate that paleoenvironment of central Myanmar did not change considerably in the Pliocene and served as a refugium for several forest/woodland dwellers at least until the early Pleistocene. The development of the proto-Ayeyarwady and proto-Chindwin drainage systems in the late Neogene of Myanmar induced the riparian environment, probably buffering against the rain shadow effect of the Indo-Myanmar Ranges. The onset of the present day aridification in central Myanmar is probably related to the Middle to Late Pleistocene sea-level changes in SE Asian region, which have had a major impact on climate, vegetation and megafauna of SE Asia.

为了探索新近纪晚期东南亚的古环境变化，我们研究了缅甸中部上新世晚期/更新世早期 Gwebin 地区哺乳动物牙釉质的稳定碳和氧同位素组成，并将结果与​​最新的中新世 Chaingzauk 的结果进行比较缅甸的哺乳动物。Gwebin 哺乳动物的稳定碳同位素值 (δ ¹³ C) 表明它们居住在从林地到草地的镶嵌环境中。C ₃浏览牛科与C ₄放牧牛科动物以及其他消耗C _{3 的}炭疽科动物、豪猪、犀牛、猪和剑齿兽的相对丰度表明树木繁茂的环境占主导地位。在缅甸中部，假设花从 C₃至 C ₄植物自与喜马拉雅造山运动有关的最新中新世至早上新世以来已​​出现。然而，目前的稳定同位素数据表明，缅甸中部的古环境在上新世并没有发生很大变化，至少在更新世早期之前一直是一些森林/林地居民的避难所。缅甸新近纪晚期原始伊洛瓦底江和原始钦德温排水系统的发展形成了河岸环境，可能缓冲了印缅山脉的雨影效应。缅甸中部今天开始干旱化可能与东南亚地区中更新世晚期海平面变化有关，这对东南亚的气候、植被和巨型动物群产生了重大影响。