75,000 years ago, humanity had been at the point of becoming extinct.
This catastrophic situation was due to the enormous explosion of the Toba supervolcano, situated in the North of the Sumatra island, in Indonesia. The power of this explosion was so big that it is considered the most violent volcanic episode of the last 25 million years.
The eruption of the supervolcano
When the Toba made eruption, it ejected an immense quantity of material into the atmosphere: 2,700 cubic kilometres, of which 800 cubic kilometres were in the form of ash. The lava flux originated from the supervolcano destructed an area of 20 thousand squared kilometres around the Toba. The ash reached about 6 thousand kilometres from the supervolcano, arriving in Africa and leaving death in its path. The ash accumulated on the Samosir island (a small island surrounded by Lake Toba, where the eruption took place) formed a 600 metres thick layer, and the ash that arrived in India (about 3,300 kilometres) formed layers 6 metres in thickness.
The consequences of the eruption
Having in mind the enormous dimensions of the Toba eruption, we can affirm that, at least on the Sumatra island, the eruption finished with all types of life that there were alive in that epoch.
The gases and the ash expelled from the eruption of the Toba that remained suspended in the atmosphere, prevented the sunlight to enter, for which the temperatures of the planet descended abruptly by 3 to 5 ºC, and continued like this for some years after the eruption. This is what we name a volcanic winter.
This sudden change in the temperatures had disastrous consequences for the life forms that lived on the planet, and the lacking sunlight provoked the death of a big part of the existent vegetation. Without comestible remainders from which to fed, many humans and animals died, and the ash made many persons die suffocated.
The almost extinction of human beings, and our DNA
Before the supervolcano eruption, it is calculated that the Homo Sapiens population was situated between 100,000 and 300,000 human beings.
Due to the ash, the lack of food and water, and the environmental effects that followed the Toba eruption, this number descended to 2,000. The humans that survived probably lived in small tribes.
We can see reflected the proofs of this almost extinction in our DNA. If we compare the DNA of two human beings we observe that it is almost identical. In contrast, between two random chimpanzees, there can be more genetic variation than in all the human population.
The fact that only 2,000 humans survived the Toba eruption explains perfectly this phenomenon. So, our civilization, made of about 7,500 million persons, comes from a group of 2,000 persons that spread throughout the planet, 75,000 years in the past.