Modern Population Explosion Traced to Pre-Industrial Roots 2000 Years Ago

The human population explosion is commonly attributed to a sudden surge in industrialization and public health during the 18^th and 19^th centuries. Now, though, scientists have found that the foundations of this population boom were actually laid back as far as 2,000 years ago.

It took hundreds of thousands of years for the human population to reach one billion as a milestone. Yet it only took another 120 years for humans to reach a grand total of two billion. During just the past 50 years, the population has swelled to a staggering eight billion.

"The industrial revolution and public health improvements were proximate reasons that more people lived longer," said Aaron Stutz, one of the researchers, in a news release. "If you dig further in the past, however, the data suggest that a critical threshold of political and economic organization set the stage 1,500 to 2,000 years ago, around the start of the Common Era. The resulting political-economic balance was the tipping point for economies of scale: It created a range of opportunities enabling more people to get resources, form successful families, and generate enough capital to transfer to the next generation."

While historians have long focused on societal changes that occurred during the Industrial Revolution to explain the human population explosion, archaeologists have looked further back in time. They found that the potential for the human population to burgeon could be traced to a subtle interaction between competition and organization. At a certain tipping point, this interaction created opportunities for individuals to gain more control over their lives and prosper, opening the door to economies of scale. For example, the Roman Empire is a classic example of passing through this threshold.

"The vast majority of people who lived under Roman rule had a life expectancy into their late 20s or early 30s," said Stutz. "A huge swath of the population was feeding, quite literally, the dynamism that was taking place in terms of economic and political development. Their labor increased the potential for providing more democracy and competition on the smaller scale. That, in turn, led to a more complex, intergenerational dynamic, making it possible to better care for offspring and even transfer resources to them."

After this tipping point was reached, the trend continued despite the collapse of the Roman Empire. This, in turn, shows that the population explosion which continues to this day started far earlier than first expected. In addition, this revised framework for the underpinnings of human population dynamics could lead to better understanding of how economic and political organization is affecting modern-day society.

The findings are published in the journal PLOS One.