Over 8.1 billion Homo sapiens currently inhabit Earth, a stark contrast to historical population lows. The near extinction of early ancestors like Homo heidelbergensis, driven by environmental challenges, highlights humanity’s resilience. Various theories propose that Homo sapiens survived critical periods, such as a cold spell in South Africa and the Toba volcanic eruption. Despite debates on population declines, evidence suggests that after agriculture emerged, human numbers have steadily increased, with projections indicating continued growth until 2084.
The Resilience of Homo Sapiens
As of now, over 8.1 billion humans inhabit our planet, marking Homo sapiens as the dominant species. Yet, this wasn’t always the scenario. Throughout history, the human population has experienced significant fluctuations, with periods during which only a few thousand individuals of our species existed. The limited genetic diversity seen in modern humans suggests that we all stem from a relatively small ancestral group.
Some archaeologists and paleoanthropologists argue that modern humans once faced a near extinction event, though experts remain divided on when this critical moment occurred. Three primary theories have emerged, each presenting different timelines and scenarios surrounding this potential extinction.
The Near Extinction of Homo Heidelbergensis
One of the earliest human ancestors, Homo heidelbergensis, is believed to have come alarmingly close to extinction. Recent research from China unveiled evidence that this species nearly vanished around 900,000 years ago. At that time, the population plummeted from approximately 100,000 to a mere 1,300 individuals, representing a staggering 99 percent decline.
The research team utilized a novel statistical approach to analyze the genetic data from 3,154 contemporary humans. By comparing their genomes, they sought to uncover significant historical population events. Their findings suggest that Homo heidelbergensis, the ancestor of Neanderthals, Denisovans, and modern humans, faced drastic population declines due to glacial periods and extended droughts. The control of fire may have played a crucial role in their eventual recovery.
Another hypothesis suggests that Homo sapiens found sanctuary in South Africa during a cold spell roughly 150,000 years ago. Archaeologist Curtis Marean proposed this idea based on population genetic calculations, indicating that only a few hundred individuals may have survived at that time. Evidence from the Pinnacle Point caves along South Africa’s coast supports this theory, revealing shellfish remains that these early humans consumed during their struggle for survival.
Meanwhile, the eruption of the Toba volcano in northern Sumatra approximately 74,000 years ago is considered one of the most catastrophic events in human history. This eruption darkened the sky with ash, reduced global temperatures, and led to the death of many plant species. Some researchers contend that only a few thousand humans managed to endure the harsh conditions that followed, surviving in regions like southern Africa.
While the Toba catastrophe theory gained traction for years, recent archaeological discoveries have raised questions about the extent of its impact on humanity. New evidence suggests that humans continued to thrive in various parts of the world, including the island of Flores, where the diminutive Homo floresiensis is believed to have survived the volcanic eruption.
Despite the differing theories, some experts, like population geneticist Stephan Schiffels from the Max Planck Institute, argue that the genetic data does not support the notion of a drastic population decrease to just a few hundred individuals in the last 300,000 years. He notes that while the human lineage may have faced peril, it cannot be definitively proven through genetic evidence.
What remains clear is that after the advent of agriculture about 11,000 years ago, humanity’s existence became increasingly secure. The global population began to surge, particularly with the onset of industrialization in the early 19th century. Projections from the UN suggest this growth will continue until 2084, when the population could reach 10.3 billion. After that, a gradual decline is expected as birth rates decrease, but with ample reserves, humanity’s extinction appears far from imminent.