Old Stone Tools Add Twist to the Extinction of Madagascar’s Megafauna

Madagascar is an natural wonder, brimming with creatures that have evolved in the island’s “splendid isolation.” But Madagascar’s endemic fauna was even more spectacular in the not-too-distant past. The island is now devoid of the enormous elephant birds, giant lemurs, dwarfed hippos, and other unusual animals that lived there. They disappeared so recently, only about one thousand years ago, that their remains are referred to as “subfossils.” How and why they were wiped out is a matter of contention, often seen as a catastrophic decline in the wake of human arrival, but a new archaeological find suggests that the downfall of Madagascar’s megafauna was a more protracted disaster.

Compared to our distant primate relatives, people haven’t occupied Madagascar for very long. The ancestors of today’s lemurs are thought to have arrived by rafting from mainland Africa around 50 to 60 million years ago, whereas the oldest known human villages only go back to around A.D. 500. Within a thousand years of these villages becoming established, every endemic species on the island over 10 kilograms was driven into extinction. Hunting, the use of fire, the spread of agriculture across the island, and other causes have been proposed without consensus, but the connection between humans and extinction is unmistakable.

Yet the record of interaction between humans and Madagascar’s long-lost fauna goes back significantly further. In a new PNAS paper, Yale University anthropologist Robert Dewar and coauthors describe two archaeological sites that add to the emerging picture of an earlier human arrival on Madagascar. Not only that, but the collected artifacts suggest that these early arrivals were hunting the island’s unique animals.

One of the rock shelters the researchers identified, known as Ambohiposa, was about as old as the earliest known villages on the island. This place seemed to be a foraging camp littered with small stone tools made of chert and obsidian, including what appear to be projectile points. The second shelter, Lakaton’i Anja, contained similar tools, but represents a series of occupations much earlier in time.

The Lakaton’i Anja site is made up of several layers of archaeological tools. From different dating techniques applied to wood charcoal, sediment, and pottery, the top assemblage dates to A.D. 1050-1350 while the lowest may go back as far as 2000 B.C. If these dates hold up, people may have been present on Madagascar for thousands of years longer than previously thought. And at this site, archaeologists found clues to what these people were actually eating during their sporadic stops.

Excavations at Lakaton’i Anja during the 1980s, as well as the new expedition in 2011, turned up the remains of small birds, tortoises, tenrecs, fish, anemones, marine clams and snails, and medium-sized lemurs. The range of animals suggests that the people who intermittently used this shelter foraged the nearby shore and gorges for food.

The collection of tools and bones adds to previously-discovered, uncertain records of an earlier human occupation on Madagascar. Ventura Perez and colleagues, for example, have described the butchered bones of extinct sloth lemurs, one of which was provisionally dated to between 417 and 257 B.C. Even if people at Lakaton’i Anja didn’t leave any signs of consuming the large, bizarre animals of Madagascar at their foraging shelter, the age of the site still supports the idea that humans were present and hunting Madagascar’s fauna long before the establishment of villages.

At the end of the new study, Dewar and coauthors call for more intense scrutiny of Madagascar’s archaeological sites “to understand the chronology, origins, geographic spread, and environmental impacts of the human occupation of Madagascar.” Lakaton’i Anja is a clue pointing to a more complicated backstory. That goes for the extinction of the island’s lost fauna, too. “[T]he view that Madagascar’s history can be sharply divided by the arrival of humans between an undisturbed Eden and anthropogenic chaos is no longer tenable,” Dewar and colleagues write. We alter habitats as soon as we step into them, true for us as any other species, but assuming that human arrival immediately causes a disastrous environmental crash no longer holds for Madagascar. The sloth lemurs and elephant birds are gone, but researchers have yet to unravel exactly what changes drove them to their irrevocable fate.

References:

Dewar, R., Radimilahy, C., Wright, H., Jacobs, Z., Kelly, G., Berna, F. 2013. Stone tools and foraging in northern Madagascar challenge Holocene extinction models. PNAS. 10, 31: 12583-12588

Perez, V., Burney, D., Godfrey, L., Nowak-Kemp, M. 2003. Box 4. Butchered sloth lemurs, in Godfrey, L., and Jungers, W. The extinct sloth lemurs of Madagascar. Evolutionary Anthropology. 12: 252-263

Perez, V., Godfrey, L., Nowak-Kemp, M., Burney, D., Ratsimbazafy, J., Vasey, N. 2005. Evidence of early butchery of giant lemurs in Madagascar. Journal of Human Evolution. 49, 6: 722-742