More than 50 million indigenous people perished by 1600

Prior to Columbus’s arrival in the Americas in 1492, the area boasted thriving indigenous populations totaling to more than 60 million people.

A little over a century later, that number had dropped close to 6 million.

European contact brought with it not only war and famine, but also diseases like smallpox that decimated local populations. In fact, a February 2019 study published in the journal Quarternary Science Reviews shows that those deaths occurred on such a large scale that they led to a “Little Ice Age”: an era of global cooling between the 16th and mid-19th century.

Researchers from University College London found that, after the rapid population decline, large swaths of vegetation and farmland were abandoned. The trees and flora that repopulated that unmanaged farmland started absorbing more carbon dioxide and keeping it locked in the soil, removing so much greenhouse gas from the atmosphere that the planet’s average temperature dropped by 0.15 degrees Celsius.

Typically, experts look to the Industrial Revolution as the genesis of human-driven climate impacts. But this study shows that effects may have began some 250 years earlier.

“Humans altered the climate already before the burning of fossil fuels had started,” the study’s lead author, Alexander Koch, told Business Insider. “Fossil fuel burning then turned up the dial.”

More than 50 million indigenous people perished by 1600

Experts have long struggled to quantify the extent of the slaughter of indigenous American peoples in North, Central, and South America. That’s mostly because no census data or records of population size exist to help pinpoint how many people were living in these areas prior to 1492.

To approximate population numbers, researchers often rely on a combination of European eyewitness accounts and records of “encomienda” tribute payments set up during colonial rule. But neither metric is accurate — the former tends to overestimate population sizes, since early colonizers wanted to advertise riches of newly discovered lands to European financial backers. The latter reflects a payment system that was put in place after many disease epidemics had already run their course, the authors of the new study noted.

So the new study offers a different method: the researchers divided up North and South America into 119 regions and combed through all published estimates of pre-Columbian populations in each one. In doing so, authors calculated that about 60.5 million people lived in the Americas prior to European contact.

Once Koch and his colleagues collated the before-and-after numbers, the conclusion was stark. Between 1492 and 1600, 90% of the indigenous populations in the Americas had died. That means about 55 million people perished because of violence and never-before-seen pathogens like smallpox, measles, and influenza.

According to these new calculations, the death toll represented about 10% of the entire Earth’s population at the time. It’s more people than the modern-day populations of New York City, London, Paris, Tokyo, and Beijing combined.