Ancient Teeth Reveal How Mammals Adapted—or Failed to Adapt—to Climate Change in Southeast Asia
New research shows that dietary flexibility helped some animals survive dramatic environmental shifts, while others vanished from local habitats
By analyzing fossil teeth, an international team of scientists has revealed how ancient mammals in Southeast Asia responded to dramatic climate and environmental changes. The study, which was published in Science Advances today, used cutting-edge geochemical techniques to investigate fossilized teeth from animals that lived between 150,000 and 13,000 years ago. The results reveal surprising insights into what they ate, where they roamed, and why some species disappeared while others survive in the region to this day.
Led by Dr. Nicolas Bourgon of the Max Planck Institute of Geoanthropology, the team applied a powerful combination of stable isotope analyses—specifically of carbon, oxygen, nitrogen, and for the first time at this scale, zinc—to fossils from Vietnam and Laos. This innovative multi-isotope approach allowed them to reconstruct detailed ecological profiles for dozens of extinct, extirpated (locally extinct), and still-living species.
“By analyzing chemical traces locked in tooth enamel, we can piece together ancient diets and environments in remarkable detail,” explains Bourgon. “And by comparing these data across time and species, we gain crucial insight into what makes some animals more resilient than others.”
Teeth as Time Capsules
Fossil teeth are more than just ancient remains; they act as biological time capsules, preserving chemical traces of what animals ate, where they lived, and how they coped with their surroundings. “In tropical environments, bones rarely fossilize, and if they do, they often lose the chemical traces we need” explains Dr. Tina Lüdecke, group leader of the Hominin Meat Consumption project at the Max Planck Institute of Chemistry and co-author of the study. “Tooth enamel, by contrast, is far more resilient. It can preserve these geochemical fingerprints for hundreds of thousands of years, acting like a prehistoric diary written in atoms”.
Using ultra-sensitive techniques, the team was able to read these chemical “diaries”, with each isotope offering a different clue:
- Carbon (δ¹³C) reveals whether animals fed in grasslands or forests.
- Oxygen (δ¹⁸O) reflects climate conditions such as humidity and temperature.
- Nitrogen (δ¹⁵N) points to an animal’s place in the food chain.
- Zinc (δ⁶⁶Zn) points to an animal’s place in the food chain and offers new insights into omnivorous diets.
Together, these signals allowed researchers to reconstruct the daily lives of animals that roamed Southeast Asia tens of thousands of years ago, offering an unprecedented look at how species adapted (or didn’t) as their world changed around them through cycles of glacial cold and interglacial warm periods. The team analyzed 141 fossil teeth from two Vietnamese sites, Coc Muoi and Duoi U’Oi, and combined them with existing data from Laos to build a region-wide picture of changing ecosystems over nearly 140,000 years.
Flexibility as a Survival Strategy
The findings reveal a clear pattern: animals that adapted their diets or foraged in different environments were more likely to survive past climate upheavals. Many species that still living in the study region today, such as sambar deer, macaques, and wild boar, showed wide ranges in isotopic values, indicating varied diets or habitats, or both.
In contrast, species that are now extinct – or at least locally extirpated - including orangutans, tapirs, and rhinoceroses, had much narrower ecological profiles. These animals tended to specialize in specific foods or environments, or both, leaving them more vulnerable to change.
“Some animals survived by being ecological generalists,” says Bourgon. “They could eat a wider range of foods or live in both open and forested environments. Others were specialists, and when their preferred habitats disappeared, so did they.”
New Light on Ancient Orangutans
Among the most fascinating results were those concerning orangutans, now restricted to Borneo and Sumatra but once widespread across Southeast Asia. Isotope data suggest these ancient apes consistently relied on fruit from closed-canopy forests over thousands of years, even if their surroundings changed around them. Their dietary specialization likely made them more vulnerable to habitat loss, both in the past and today.
“Even though modern orangutans can turn to alternative foods during hard times, their survival still depends on intact forests,” says Mai Huong, co-author from the Anthropological and Palaeoenvironmental Department of Vietnam’s Institute of Archaeology. “It looks like this has been true for tens of thousands of years.”
Lessons for Conservation Today
Southeast Asia is currently experiencing the highest rate of deforestation of any tropical region in the world, threatening many of the same species studied in this research. By uncovering which animals were flexible in the past and which were not, the study provides new context for conservation strategies.
“Understanding how species coped with past environmental pressures can help us predict their resilience today,” says Patrick Roberts, Director of the Department of Coevolution of Land Use and Urbanisation at MPI-GEA and co-author of the study. “Our work highlights the importance of protecting not just species, but the ecological conditions they depend on, with ramifications for considering land use changes in the 21st century.”
The researchers argue that long-term isotope studies could become a valuable tool for conservation biology, especially in biodiversity hotspots facing rapid climate change and habitat destruction.
A Call for Broader Perspective
This study not only reveals the deep ecological histories of Southeast Asia’s mammals, it also showcases the power of interdisciplinary science. By blending archaeology, paleontology, chemistry, and conservation, the research team offers a new way of understanding the complex factors behind extinction and survival.
“This is about more than just ancient animals,” says Bourgon. “It’s about learning from the past to protect the future.”
