Prehistoric people spread like an ‘invasive species’ in South America

The first people to South America found the continent towards the end of the Ice Age, inhabited by creatures such as giant ground sloths and car-sized armadillos.

WASHINGTON // When the first prehistoric people trekked into South America towards the end of the Ice Age, they found a wondrous, lush continent inhabited by all manner of strange creatures, such as giant ground sloths and car-sized armadillos.

These hunter-gatherers behaved like an “invasive species”, with their population growing then crashing as they relentlessly depleted natural resources.

Only much later, after forming fixed settlements with domesticated crops and animals, did population growth surge ahead.

Those are the findings of research published last week in Nature journal, which provides the most comprehensive look so far at the rise of human beings in South America, the last habitable continent colonised.

Two phases have been identified. The first was about 14,000 to 5,500 years ago, with the human population estimated at 300,000; the second phase was 5,500 to 2,000 years ago, with the population peaking at a million.

“Humans are just like any other invasive species,” said Elizabeth Hadly, biology professor at Stanford University in California. “If we use up our resources, we will decline.”

The researchers rebuilt the history of human population growth in South America using radiocarbon-dating data from 1,147 archaeological sites.

Our species appeared in Africa about 200,000 years ago, then spread to Europe and Asia and eventually crossed to the Americas 15,000 to 20,000 years ago, using a land bridge that once connected Siberia and Alaska.

The first phase of colonisation in South America coincided with the extinction of many large animals, including relatives of elephants, sabre-toothed cats, ground sloths, armadillos and flightless birds.

In this period, human populations underwent “boom-and-bust cycles” as people exhausted plant and animal resources, said Amy Goldberg, a Stanford anthropologist.

Some began domesticating animals and growing crops, including squash and peppers. But most remained nomadic.

About 5,000 years ago, people settled into more stable societies, launching 3,000 years of growth when the continent’s population tripled, Ms Goldberg said. “We find that it is the large settlements, not merely stable food sources, that allow humans to conquer their environment and grow unbounded,” she said. “Most lived in modern Peru, ­Ecuador and northern Chile, but some settled in Patagonia.”

*Reuters