By looking at our DNA, scientists have discovered that there was, apparently, a “bottleneck” in human evolution — a time when the population of homo sapiens drastically died out, leaving only a couple of thousand individuals, at most. From a BBC News article: “The small genetic diversity of modern humans indicates that at some stage during the last 100,000 years, the human population dwindled to a very low level. It was out of this small population, with its consequent limited genetic diversity, that today’s humans descended.”
Some have hypothesized that a volcano, erupting in or near the Great Rift Valley of Africa, at a time when most of our ancestors still lived there, is what nearly did us in.
A time traveler from an alternate timeline (the “real timeline,” he insisted) told me what really happened.
What really happened was that scientists from the real timeline (I’ll just use his terminology here, to make things easier) learned how to travel back in time. One of the first things they wanted to see was the origin of the species, so they set their dials and whatsis to take them to the Great Rift Valley, 70,000 years ago.
The super-evolved, 21st century germs that they carried on their bodies wiped out almost every person they met. Only a few survived. These survivors, along with the time travelers themselves, are the ancestors of all humanity in this, our inferior, secondary timeline.
My time traveler, who arrived at my place by accident and quickly stepped back into the timestream after chatting a bit, explained to me that he was trying to correct this error. He’s sort of like that Quantum Leap guy. It’s his job to set things right. Once he has finished his work, we will all cease to exist, and the “real” timeline, with more genetically diverse humans, will snap back in place.