This question has been raised time and time again in science fiction and is even mentioned in the Bible. If a huge catastrophe or disaster was to occur that wiped out all but two people on Earth, what would happen next? The fate of humanity would rest on the shoulders of one man and one woman - and on their reproductive organs.Could humanity emerge from the ashes like a phoenix if only two people were left on Earth? Before you let your imaginations run wild, it turns out that the answer is actually, no. But read on to find out why!Adam, Eve and all the othersIt might sound pretty general but in theory, it is actually possible, if their reproductive organs were working at the optimal level. A certain ‘birds and the bees’ conversation from your biology lessons may be coming to mind right about now…‘Adam and Eve: Would such mass repopulation really be possible? Fred De Noyelle \/ GODONG \/ Getty Images’In practice, however, things are actually a lot different even if Adam and Eve’s story suggests the complete opposite. In any case, a journalist from the BBC was so interested in this question that she carried out extensive research on the topic. And her research confirmed that the biggest issue humanity would face if they needed to repopulate the planet would be incest. This is due to the fact that new couples, who would consequently be formed by the first generation of children born, would all actually be siblings, meaning that the endeavour would be extremely shaky and problematic.Fatal consequencesIncest is not only completely frowned upon from an ethical point of view, but it is also extremely problematic and threatening for the development of a species. According to a study carried out on children born between 1933 and 1970 in former Czechoslovakia, incest proved to have disastrous consequences. 46 per cent of children whose parents were first cousins were born with quite severe disabilities and, of these children, one in seven died before they reached adulthood.What caused this? A lack of genetic mixing. Even though we have been able to continuously adapt to new conditions over the course of our evolution, mixing genetic material and DNA is fundamental should a species hope to survive. In closed societies where people who are genetically very close end up reproducing, lots of birth defects continue to be recorded in newborn children.Two people aren’t enoughTherefore, in order to successfully repopulate the planet, two people just wouldn’t be enough, even if they were in the same place at the same time, were both fertile, consented to sexual intercourse and were both in good health. For a higher chance of success, Dr. Stephen from Durham University argues that we would need between 500 to 5,000 people.So, we can only hope that the next big apocalypse will leave enough genetic material behind for us to keep humanity going. If not, we could end up kissing a functional human race goodbye! Science has also only just revealed how probable it is for the Earth to fall this year.