Deciphering mitochondrial DNA shows that about 70 thousand years ago, the human species almost disappeared from the face of the Earth. The population dropped to about ten thousand individuals. Traces of similar events are found in the genomes of East African chimpanzees, South Asian tigers and orangutans. This means that at this time a grandiose natural disaster occurred on the planet, which destroyed many species and actually formed modern man.
Bottleneck and gene drift
In 1993, an international team of scientists analyzed for the first time mitochondrial human DNA and found traces of two important processes - bottleneck and gene drift. The first indicates a sharp decline in the population and depletion of the gene pool - many gene variants simply disappear along with their not very successful carriers. The second process is typical for small populations, where the frequency of occurrence of a particular gene variant changes rapidly and completely randomly. Any even the most insignificant demographic event - say, the sudden death of only one adult childless man - can permanently change the color of the eyes or hair of future members of his tribe. The interpretation of these data is unambiguous: 50-70 thousand years ago, humanity was on the verge of extinction. The population dropped sharply to ten thousand people and remained small for quite some time.
Four years later, traces of the same processes were found in the genome of East African chimpanzees. The genetic diversity of mitochondrial DNA in monkeys was as low as in humans. In 2004, when decoding the genome of South African tigers, researchers obtained very similar data. And then signs of a bottleneck and gene drift were found in the DNA of orangutans living in Sumatra and Borneo. Everything suggests that in the distant past, animals, together with our ancestors, experienced a global natural disaster.
Long volcanic winter
There are twenty supervolcanoes on Earth, whose eruption can cause climate change on the planet. Swiss scientists have found that these volcanoes wake up once in a hundred thousand years, and the last such eruption happened about 75 thousand years ago, just on the eve of the human bottleneck. We are talking about the Indonesian volcano Toba. As a result, a huge Lake Toba appeared in Sumatra, deposits of volcanic ash formed over an area of almost forty million square kilometers. This ash is even at the bottom of the African lake Malawi, seven thousand kilometers from Sumatra, and a sharp jump in the content of sulfuric acid salts recorded in ice cores from Greenland also falls on this period - 74 thousand years ago. There were so many ashes that, once in the atmosphere,he blocked sunlight for several months and a volcanic winter set in, suggests an international team of researchers. The climate did not spoil our ancestors anyway - then there was the last ice age. After the eruption of Toba, the average annual temperatures reached a minimum, falling, according to various sources, by 5-15 degrees Celsius.
Was there a disaster?
This explains why the first Homo sapiens, who left Africa 125 thousand years ago, became completely extinct, and the number of those who remained on their native continent dropped to a critical ten thousand individuals. However, there is evidence that contradicts the hypothesis of the great and terrible Toba. In excavations in southern India, American anthropologists have discovered Paleolithic tools both under and above the layer of volcanic ash. A similar situation is with the sites of ancient people on the coast of South Africa. The tools found there indicate that our ancestors settled in these places before, during and after the disaster. That is, there was no break in archaeological cultures synchronous with the eruption of the supervolcano. Moreover, the disaster seemed to have bypassed the Neanderthals, who, after the awakening of Toba, reached their heyday, albeit a short one. Having studied the same Tobian ash raised from the bottom of Lake Malawi, scientists concluded that its concentration is insufficient to seriously affect the local ecosystem. If there were a lot of ash, and the temperature in the region dropped by at least four degrees, a significant part of the biota would become extinct in the upper layers of the lake. But, judging by the deposits, nothing of the kind happened. Consequently, the eruption of Toba and the alleged volcanic winter could not have caused the bottleneck through which humanity passed. However, researchers have no doubts that our ancestors nearly died out about 70 thousand years ago. Some kind of global natural disaster really happened on Earth. Which one exactly is an open question.that its concentration is insufficient to seriously affect the local ecosystem. If there were a lot of ash, and the temperature in the region dropped by at least four degrees, a significant part of the biota would become extinct in the upper layers of the lake. But, judging by the deposits, nothing of the kind happened. Consequently, the eruption of Toba and the alleged volcanic winter could not have caused the bottleneck through which humanity passed. However, researchers have no doubts that our ancestors nearly died out about 70 thousand years ago. Some kind of global natural disaster really happened on Earth. Which one exactly is an open question.that its concentration is insufficient to seriously affect the local ecosystem. If there were a lot of ash, and the temperature in the region dropped by at least four degrees, a significant part of the biota would become extinct in the upper layers of the lake. But, judging by the deposits, nothing of the kind happened. Consequently, the eruption of Toba and the alleged volcanic winter could not have caused the bottleneck through which humanity passed. However, researchers have no doubts that our ancestors nearly died out about 70 thousand years ago. Some kind of global natural disaster really happened on Earth. Which one exactly is an open question. Consequently, the eruption of Toba and the alleged volcanic winter could not have caused the bottleneck through which humanity passed. However, researchers have no doubts that our ancestors nearly died out about 70 thousand years ago. Some kind of global natural disaster really happened on Earth. Which one exactly is an open question. Consequently, the eruption of Toba and the alleged volcanic winter could not have caused the bottleneck through which humanity passed. However, researchers have no doubts that our ancestors nearly died out about 70 thousand years ago. Some kind of global natural disaster really happened on Earth. Which one exactly is an open question.
Alfiya Enikeeva
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