The Toba Catastrophe Theory: When Humanity was on the brink of extinction
In our DNA there is the trace of an apocalyptic volcanic eruption that occurred 75 thousand years ago that killed millions of people. Is this the catastrophe linked to the extermination of the First Men present in myths around the world?
In the legends of all religions around the world, there is the memory of a dramatic moment for Humanity. The Gods, tired of its people's sins, decides to unleash a terrible punishment upon them, from which only a few chosen ones will be saved to create the present society. The Bible's reference to the Great Flood is clear, believed by many to be a real event linked to the melting of the ice from the last glaciation. This thaw marked the end of the Pleistocene and the beginning of a new era, the Holocene, in which we live today. Despite the climate variability of the Holocene, it is generally accepted that this geological epoch is characterized by milder and less extreme weather compared to the Pleistocene, which was disrupted by terrible glacial periods that completely transformed the planet's face and its fauna. Indeed, the differences between the two eras are vast, and the Holocene appears more suitable for a certain type of civilization based on artificial constructions and a sedentary lifestyle.
This was not the case during the Pleistocene when the availability of vast coastal areas created by the lowering of sea levels up to 130 meters allowed humans to inhabit large portions of caves and crevices that are now submerged. Not to mention the possibility of nomadism in regions where rivers became true water highways during the spring snowmelt. Certainly, the sea level rise of 130 meters caused a real upheaval in the human environment, which suddenly found itself without much of its habitable territory: an event that led to the creation of the Atlantis myth.
The Great Flood, according to authoritative theories linked to the shifting of the Poles and the reversal of the Earth's axis, could theoretically symbolize the irreparable loss of that territory now swallowed by the sea, where only those "closest to the celestial deities," namely the inhabitants of mountainous and hilly regions at higher elevations, survived. If the Pole shift occurred, it must have been a temporally limited event: according to incredible Egyptian chronicles cited by historian Manetho, the Sun rose in the west a couple of times in 25,000 years and deviated its course another four times, suggesting it was a "nearly natural" event, not catastrophic. In fact, Egyptian annals do not show colossal devastations, just temporary nuisances, nothing capable of exterminating an evolved species. If such a geographical Pole reversal occurred, the inertia of the ocean masses would have continued their course, overwhelming all continents in their path like a planetary tsunami.
But the story of Noah also tells us that it rained for "forty days and forty nights," then the waters began to recede. Within a year, Noah was able to disembark on Ararat with his family and animals, and life began to resume. Apart from physical doubts about where all the water that Yahweh sent to Earth ended up, the timeline is not convincing. The disappearance of the Pleistocene megafauna did not happen in a few months but over thousands of years, with the gigantic animals of the ice age gradually making way for current living beings. Fossil finds tell us that representatives of the megafauna lived until protohistoric times (like the Giant Deer, extinct in Ireland in 7000 BCE) or even historical times (the mammoth in dwarf form lived on Wrangel Island in the Arctic Sea until 1700 BCE). Furthermore, animals have an almost paranormal ability to "sense" disasters: it is known that during the 2004 Sumatra tsunami, animals took refuge hours before the devastating wave arrived, heading for higher ground as if they sensed the danger. This ability seems to be a prerogative of all animal creatures, not just the more evolved ones. So what does the biblical story and all the other flood stories that speak of an exterminating deluge allude to?
Perhaps, the cataclysmic event should not be associated with a flood or a tsunami or the shifting of the Poles, but with something different, more devastating in numerical terms. To discover what apocalypse occurred in human history, we are helped by two seemingly unrelated sciences: Genetics and Volcanology. Through their studies, we can leap into the past, literally reading the events our species experienced through DNA analysis and the geological remains of prehistoric volcanic eruptions.
The first science comes to our aid with a surprising discovery. The genetic study of the human genome has led to the analysis of millions of DNA fragments, some of which have shed light on our past. The human species formed about 250,000 years ago, but only about a hundred thousand years ago did it begin to show anatomically modern characteristics. This genetic diversity can be explained in simple terms: when a new species forms, there are always various genetic branches with different characteristics, and evolution will determine which of these traits is best suited to live in a certain ecosystem. For a long time, humans lived in distinct groups until a certain moment when an event led to the extinction of almost all groups except one, of which modern humans are the heirs.
The Progenitor of All Modern Humans: Mitochondrial Eve
Mitochondria are cell components that synthesize oxygen and produce energy: they are transmitted entirely through a matriarchal line. They are organelles with their own autonomous genetic heritage (mt-DNA) that, unlike the "normal" genetic heritage (transmitted 50% from the mother and 50% from the father), are transmitted almost 100% by the mother. At birth, every human being possesses the mitochondria of the mother, and if this person is female, she will transmit her maternal mitochondria to her children. Males cannot transmit these mitochondria (which are destroyed by the ovum at fertilization), while women can pass on mt-DNA to daughters, granddaughters, and so on. Naturally, her mt-DNA is that of her mother, grandmother, great-grandmother, etc. Going back in time through countless analyses of all the world's peoples, geneticists have finally found the "first woman" from whom all humanity descends. Somewhat improperly named Eve, this mitochondrial mother was a woman who lived about 150,000 years ago in a population of about 20,000 people in an area of East Africa, located roughly between southern and western Tanzania. Her uniqueness lies in the fact that during that period, a "Bottleneck" occurred, meaning the human species was devastated by a significant die-off, to the point that only one woman, at least theoretically, survived extinction. Of course, there are many scientific clarifications to be made, first and foremost that Mitochondrial Eve probably was not unique but could refer to a group of sisters or related women (such as those of a small tribe). But this fact is significant: a mass extinction wiped out many human races very different from ours, although the reason for this extinction is unknown. Is this the mythical memory of the flood that, according to legend, annihilated sinners, giants, cyclopes, and so on? The extinction of 150,000 BCE is only the first catastrophe involving Humanity. A second Bottleneck, perhaps even more shocking, is found in the genes of the human race.
This time, males are the focus. The Y-Chromosomal Adam is the most ancient male ancestor genetically traceable, seemingly living about 75,000 years ago, half the time of Mitochondrial Eve. The Y chromosome is notoriously transmitted from father to male children, as males determine a newborn's sex. Therefore, by analyzing the Y chromosomes of many people, it is possible to discover the modifications over time, and like mt-DNA, scientists have traced the oldest male ancestor along the common patrilineal line. According to studies by researchers at Stanford University on 93 genetic polymorphisms found in a thousand males from 21 regions of the world, this ancestor was a theoretical man (again, somewhat improperly named Y-Chromosomal Adam) who lived during one of the greatest upheavals experienced by our planet.
The Toba Catastrophe
Lake Toba is an idyllic body of water about 100 km long and 30 km wide, located at the center of the large island of Sumatra, Indonesia. In a territory periodically devastated by immense earthquakes (like the catastrophic one in 2004), Lake Toba is what remains of a supervolcano that caused a series of terrifying eruptions 800,000, 500,000, and 75,000 (± 4,000) years ago. This last eruption was particularly cataclysmic and brought about global climatic changes that could have heavily influenced Humanity's fate. In 1949, Dutch geologist Rein van Bemmelen analyzed the Lake Toba caldera and made an important discovery: all around this stunning tropical area, rich in lush vegetation, extended hundreds of meters of ignimbrite sediment. The same ignimbrite, a typical magmatic product composed mainly of rhyolite and derived from catastrophic Plinian eruptions, was found in India, where the layer was six meters thick, and in China, where it reached four meters. Even the ocean floor of the Indian Ocean and the Bay of Bengal show evident traces of the same ignimbrite.
It was immediately clear that the eruption of 73,000 BCE was terrifying, and according to many studies conducted over the years, like those by researchers Bill Rose and Craig Chesner from Michigan Technological University, the volume of erupted material was about 2,800 km3: globally the worst eruption of the last two million years, classified with a magnitude of 8 on the Volcanic Explosivity Index (the second most catastrophic volcanic activity ever). The global effects were immense, temperatures dropped by 7-15 degrees, and a volcanic winter worsened Pleistocene glacial conditions. Life in Indonesia simply disappeared, and animals and plants throughout Southeast Asia suffered severe damage. The ash suffocated animals and poisoned water sources, plants covered in soot died without performing photosynthesis: a doomsday scenario similar to the end of the dinosaurs.
If Toba did not completely exterminate humans, it came very close. The population was reduced to a few tens of thousands of individuals, and that common ancestor, Y-Chromosomal Adam, probably lived during this apocalypse. Despite having Mitochondrial Eve in their genes, humans today are children of Y-Chromosomal Adam, making us the descendants of those few thousand survivors who escaped extinction.
The most incredible story of Toba's eruption comes from the findings of two paleoanthropologists, Stanley Ambrose and Goade Wilson. In 1998, Ambrose analyzed paleoclimatic, archaeological, and genetic data, discovering that the mass extinction around 73,000 BCE left a profound mark on our DNA. This small number of people may have migrated to India, and about 35,000 years ago, they may have settled in the Middle East, mixing with Neanderthals. The fusion of the Y-Chromosomal Adam group with the first "Eve" group is probably the origin of modern humans. Around 40,000 BCE, people likely moved to East Asia, Europe, and Australia. In South Africa, traces of human presence exist from around 160,000 BCE, but we have little knowledge of their evolution. Humans lived in these regions at least until 75,000 BCE when Toba wiped out a large portion of the population. It's incredible that we find ourselves here, and it is the most striking demonstration of how natural disasters influenced human development, forcing our ancestors to adapt and evolve in challenging conditions.
The eruption of Toba and its aftermath left an indelible mark on human genetics and our evolutionary history. It forced the small, surviving populations to adapt and evolve in response to extreme environmental changes. The combined forces of natural selection and genetic drift played a crucial role in shaping the genetic diversity we observe in modern humans today. These findings provide a unique perspective on the resilience and adaptability of our species in the face of catastrophic events.
