New York: Global climate change and biological factors such as diseases, and not the advent of agriculture, controlled long-term growth of human population for most of the past 12,000 years, says a new study.
The researchers found that prehistoric human populations of hunter-gatherers in a region of North America grew at the same rate as farming societies in Europe.
The findings challenge the commonly held view that the advent of agriculture 10,000-12,000 years ago accelerated human population growth.
"Our analysis shows that transitioning farming societies experienced the same rate of growth as contemporaneous foraging societies," said study co-author Robert Kelly, professor of anthropology at University of Wyoming in the US.
"The same rate of growth measured for populations dwelling in a range of environments, and practicing a variety of subsistence strategies, suggests that the global climate and/or other biological factors -- not adaptability to local environment or subsistence practices -- regulated long-term growth of the human population for most of the past 12,000 years," Kelly noted.
While the world's human population currently grows at an average rate of one percent per year, earlier research had shown that long-term growth of the prehistoric human population beginning at the end of the Ice Age was just 0.04 percent annually.
For their research, the scientists analysed radiocarbon dates from Wyoming and Colorado that were recovered predominantly from charcoal hearths, which provide a direct record of prehistoric human activity.
For humans in the region that is now Wyoming and Colorado between 6,000 and 13,000 years ago -- people who foraged on animals and plants to survive -- the analysis showed a long-term annual growth rate of 0.041 percent, consistent with growth that took place throughout North America.
During that same period, European societies were farming or transitioning to agriculture, yet the growth rate there was essentially the same.
"The introduction of agriculture cannot be directly linked to an increase in the long-term annual rate of population growth," the researchers wrote.
The research was published in the journal Proceedings of the National Academy of Sciences.
