Madagascar is the fourth-largest island in the world. Like other long-isolated land masses, it developed plants and animals that were slightly to far different than those on the continents. In Madagascar’s case, many of the animals grew to giant versions of their land cousins. Most of the other isolated islands lost their unique species tens of thousands of years ago due to climate change or invasive species, with the worst one being humans. That was true in Madagascar’s case with one big exception – its giant animals managed to survive until a mere 1,000 years ago. A group of researchers has identified the cause of their recent and rapid extinctions … and it’s not what you might think.
“Giant 10-foot-tall elephant birds, with eggs eight times larger than an ostrich’s. Sloth lemurs bigger than a panda, weighing in at 350 pounds. A puma-like predator called the giant fosa.”
In a new study published in the Journal of Human Evolution and summarized in a detailed article in The Conversation, University of Massachusetts Amherst researchers Nick Scroxton, Postdoctoral Research Scholar in Paleoclimatology, Laurie Godfrey, Emeritus Professor of Anthropology, and Stephen Burns, Professor of Geosciences, describe some of the giant species whose fossils are found on Madagascar, methodically list the possible reasons why they died of, and eliminate each one. Climate change? They analyzed the layers of stalagmites growing from cave floor and found no signs of drought during the period of rapid decline of giant animals between 700 and 1000 CE.
Humans? It had to be humans, right? Especially since other researchers recently put the arrival of modern humans on Madagascar at 10,500 years ago, much earlier than previously thought. However, DNA analysis shows those humans completely disappearing from the island well before the giants disappeared. New waves arrived from Indonesia 3,000 to 2,000 years ago and mainland Africa 1,500 years ago. Not surprisingly, cut marks on fossils showed that the hungry humans definitely ate the local animals, but in small quantities. Were they diet conscious? Early environmentalists? The researchers don’t say, but confirmed they didn’t eat them into extinction.
However, the diet of these humans indirectly contributed to the fall of the animal giants. How? The researchers found that the forest-dominated environment of Madagascar changed to a grass-dominant one right about at the time of the extinction. Why? The humans brought agriculture with them, cutting down the forests for rice paddies and farms. As more land was put into use, the human population grew and the giants were forced into smaller and smaller patches with less and less food and quickly died off.
“We offer a new hypothesis, which we call the “Subsistence Shift Hypothesis,” to explain megafaunal decline and extinction in Madagascar … The interval between 700 and 900 CE, when the pace of megafaunal decline quickened and peaked, coincided with this economic transition. While early megafaunal decline through hunting may have helped to trigger the transition, there is strong evidence that the economic shift itself hastened the crash of megafaunal populations.”
So, the economic decision to fatten humans with grain starved the giant animals of Madagascar less than 1,000 years ago and in a period of just 200 years. Is there a lesson to be learned from this discovery?
Or is it too late?