When Christopher Columbus made landfall in the Americas on Oct. 12, 1492, he encountered Indigenous Lucayans living on the Bahamian island now called San Salvador. Columbus wrote in his diary about "great multitudes of men" who greeted him that day, bartered with him and told him about other groups who lived on nearby islands.

But within a few decades after Columbus' arrival, the Indigenous people of the Americas were decimated by what anthropologist Eric Wolf called the "Great Dying" — a combination of epidemic disease, warfare and enslavement that led to a rapid decline in the Native population.

For centuries, researchers have been trying to figure out how many Indigenous people lived in the Americas just prior to the fateful arrival of European colonizers.

The answer to that question has been surprisingly elusive, and estimates based on historical censuses, archaeological sites and land carrying capacity in the Western Hemisphere have varied wildly.

Recent research into Native American demography has revealed that the population peaked several centuries before Europeans showed up on the shores of North America — and that if Europeans had arrived at that peak, the entire history of the continent may have been different...