For much of human history, life was remarkably brief. If we ponder the question, “How Long Have Humans Been On Earth?”, it’s crucial to understand the context of early human existence, characterized by incredibly short life expectancies. For the vast majority of our journey as a species, average life expectancy at birth hovered around a mere 10 years. To illustrate, Iron Age France, spanning from 800 BCE to approximately 100 CE, saw an estimated life expectancy of only 10 to 12 years. Such stark figures highlight the immense challenges faced by early human populations simply to sustain themselves. A staggering birth rate of about 80 live births per 1,000 people would have been necessary just for the human species to survive under these conditions. To put this into perspective, even today’s high birth rates, observed in some sub-Saharan African nations, only reach about 35 to 45 live births per 1,000 population.
Early Human Existence and Population Challenges
These short lifespans directly impacted the growth of the human population. It was a slow and arduous process. Consider the Roman Empire, stretching from Spain to Asia Minor, which around 14 CE, is estimated to have had a population of 45 million. However, some historians propose figures twice as high, demonstrating the inherent uncertainties in estimating populations from ancient historical periods.
By 1650, the global population had only risen to approximately 500 million. This modest increase from an estimated 300 million around 1 CE reveals an average annual growth rate that was actually slower than that of the period from 8000 BCE to 1 CE. One significant factor contributing to this unusually slow growth was the Black Death. This devastating plague, while famously associated with 14th-century Europe, may have originated in western Asia around 542 CE and subsequently spread outwards. Experts believe that the sixth century plague decimated half of the Byzantine Empire, resulting in an estimated 100 million deaths. Such dramatic population fluctuations over extended periods significantly complicate efforts to accurately estimate the total number of people who have ever lived on Earth since humans first appeared.
Milestones in Population Growth
However, around 1800, a turning point was reached. The world population surpassed the 1 billion mark and has since experienced exponential growth, reaching our current estimate of 8 billion in 2022. This remarkable surge is largely attributed to advancements in public health, medicine, and nutrition. These improvements have drastically lowered death rates, allowing more individuals to live well into their reproductive years and beyond, fundamentally changing the trajectory of human population growth.
Estimating the Total Number of Humans
To approach the question of “how long have humans been on earth” from a population perspective, and to estimate the total number of humans ever born, we need to consider population sizes at different points throughout prehistory and history, coupled with assumed birth rates for each period. Let’s start with a simplified, albeit unlikely, scenario: the very beginning with just two individuals. While human descent from only two individuals is improbable, this minimalist approach simplifies our estimation process.
A significant challenge arises from the patterns of population growth themselves. Did population size increase to a certain level and then fluctuate wildly due to factors like famines and climate shifts? Or did it grow at a more consistent rate? While definitive answers remain elusive, paleontologists have proposed various theories. For estimation purposes, a constant growth rate is often assumed for each period leading up to modern times. Birth rates are estimated at 80 per 1,000 population annually up to 1 CE, and then at 60 per 1,000 from 2 CE to 1750. Subsequently, rates declined to below 20 per 1,000 in the modern era.
This semi-scientific method yields an estimated total of approximately 117 billion births since the emergence of modern humans. The period from 190,000 BCE to 1 CE is particularly crucial in this estimation, yet unfortunately, knowledge about population size during this era remains limited. If there is a potential weakness in this estimation, it might lie in underestimating the number of births. The assumption of constant population growth, rather than potentially large fluctuations in earlier periods, could lead to an underestimation of the average population size during those times.
The Percentage of Humans Alive Today
Considering the current global population of around 8 billion, the estimated 117 billion total births implies that those alive in 2022 constitute nearly 7% of all humans who have ever lived. Given that modern humans have existed on Earth for approximately 200,000 years, this percentage is surprisingly significant.
As ongoing archaeological discoveries are made and analyzed using increasingly advanced techniques, our understanding of human population history is likely to expand, enabling us to refine this fascinating and ever-evolving proposition: how long have humans truly been on this Earth and what does our population history reveal about our journey?
