Dyani Lewis
Dyani Lewis is a freelance science journalist based in Melbourne, Australia.
Recent splashy headlines claiming that humans arrived on the Indian Ocean island of Madagascar as early as 10,000 years ago are almost certainly wrong.
That’s according to a new study of freshly excavated animal bones, the largest of its kind to be conducted on Malagasy fossils.
Throughout the 20th century, investigations into human occupation of Madagascar painted a picture of seafaring humans arriving on the remote island between 2000 and 1350 years ago.
But in recent years, people have claimed that settlement got underway much earlier.
Most of these claims rest on analyses of bones from long-dead animals. Find a bone with marks that can be attributed to human butchery, date the bone, and you’ve potentially added thousands of years to the estimate of when humans first set foot on Madagascar.
The most recent of these – a study of seven bones, three new, from the extinct elephant bird pushed the date of human occupation back by several millennia.
The timing matters. Earlier dates suggest that humans could have happily co-existed with megafauna – giant lemurs, giant tortoises, hippopotamuses, crocodiles and elephant birds – rather than being the agents of their demise.
The claims are dubious, according to Atholl Anderson from the Australian National University, who led the new study, published in the journal PLoS ONE.
“Standard methodologies aren’t reliable enough in distinguishing what might be anthropogenic from what might be natural damage,” he says. “It’s a long-standing problem in archaeology.”
To sort genuine tool marks from damage made by other causes, Anderson and colleagues went for quantity. They examined bones from fresh excavations at three sites in southwest Madagascar where early animal butchery has been reported, as well as fossils from museum collections. In all, some 3000 bones were scrutinised.
In many instances, marks couldn’t be easily categorised. That, according to Anderson, is why it’s essential to look at large numbers of bones.
“Three bones is ridiculous,” he says.
The team found that the only bona fide human butchery marks – with crisp edges and v-shaped grooves – were from bones dating to 1200 years ago, at the earliest. None of those were on fossils from megafauna, which went extinct around that time.
They also discovered that even with the most careful excavation methods, bones ended up with small nicks and cuts. Other marks were likely caused by scavengers gnawing, or by roots and ground movements in the intervening centuries.
Context also matters. “You have to look at the broader picture,” says Anderson.
The new study’s findings fit with all other evidence from the island. No butchery tools, no pottery or other artefacts, and no genomic evidence exists of human occupation of Madagascar prior to around 1500 years ago. Pollen and ash sediments – which indicate vegetation and fire regime changes – also point to this later date.
Taken together, Anderson and colleagues suggest that humans settled Madagascar between 1350 and 1100 years ago.
