While we’ve lasted hundreds of thousands of years, there was a good chance that 800,000 years ago, humans could have become extinct. 

According to immunologist Professor Luke O’Neill, roughly 800,000 years ago there were just 1,300 couples populating the Earth. 

“98.7% of our ancestors were wiped out – isn't that strange,” he told Show Me the Science. 

“The population shrank dramatically and it created what's called a bottleneck. 

“For quite a long time, there were very small numbers of homo-sapiens and the group that were descended from in Africa. 

“Then recovery begins, and the population grows and grows.” 

It is not clear, however, why the population shrunk so dramatically hundreds of thousands of years ago. 

Climate change and near-extinction

Prof O’Neill said “massive” changes in the climate could have influenced possible extinction. 

“The Earth was covered in ice sheets and glaciers and there was a massive Ice Age around that time, [researchers] reckon,” he said. 

“That drop in temperature meant droughts, that mammoths and giant sloths became extinct. 

“One reason for this drop in population size [might have been] that the animals that we were living on were dying off and [there was] less food. 

“Part of the reason that our population [shrank] was we began to starve.” 

Prof O'Neill said there is speculation that the survivors had discovered fire and harnessed it for warmth to survive the changing climate. 

“Obviously, it's based on speculation or habits, but many experts agree with this – some controversy, it must be said,” he said. 

The population drop continued for roughly 200,000 years before it began to increase once again, according to Prof O’Neill. 

“Overall, the consensus is that this bottleneck in our population happened around about 800,000 years ago,” he said. 

“They reckon that the ones who survived this catastrophe 800,000 years ago, they reckon the three main subspecies of hominids began to evolve,” he said. 

“All three must be must have been able to survive the catastrophic climate change and homosapiens eventually appears in Africa around about 300,000 years ago.” 

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