Genetics are fascinating.
These days, people love to find out where their ancestry has come from. But a recent study shows something particularly surprising: All modern humans are descended from one couple who lived between 100,000 and 200,000 years ago.
How exactly did this happen, and where did the rest of the human race go? The answer is fairly simple: There was a massive, catastrophic event that wiped out almost all the living humans at the time.
And it’s not just humans.
A substantial number of animal species — about 90 percent — all began breeding at around the same time, roughly 100,000 to 200,000 years ago. These species managed to survive whatever catastrophe occurred and went on to spread their lineage to almost all human and animal life on the planet.
It’s a baffling idea that throws modern evolution theories for a loop. Up until now, scientists weren’t aware of a catastrophic event that recently in the planet’s history.
The last one we know of was the one that wiped out the dinosaurs. But that was much longer ago — about 65 million years. This is the first evidence that another similar event happened much more recently, essentially “restarting” life on Planet Earth. This life would eventually become life as we know it.
The study makes way for a new theory about human evolution, wherein humanity “resets” periodically.
This is big news for human genetics.
“At a time when humans place so much emphasis on individual and group differences, maybe we should spend more time on the ways in which we resemble one another and the rest of the animal kingdom,” said Dr. Mark Stoeckle, one of the researchers in charge of the study.
This Goes Beyond Humans.
In basic terms of DNA, we’re much more like animals than we think.
“Culture, life experience, and other things can make people very different, but in terms of basic biology, we’re like the birds,” Stoeckle said. “The ‘mitochondrial DNA’ examined in the research is that which mothers pass down from generation to generation and it showed the ‘absence of human exceptionalism.’
“One might have thought that, due to their high population numbers and wide geographic distribution, humans might have led to greater genetic diversity than other animal species. At least for mitochondrial DNA, humans turn out to be low to average in genetic diversity.”
The scientists made a couple of discoveries by analyzing the DNA sequences of 100,000 species across the globe, including humans: Almost all modern animal life began at roughly the same time, and we’re actually not becoming more genetically diverse as time goes on.
The basic idea is that small parts of our DNA can be found in millions of species, from human to animal life.
Essentially, certain genetic patterns, like our mitochondrial genome, that are inherited from our mother show unique variations in a genetic line. By following these variations, we can conclude that they lead back to a single ancestor.
The bottom line? Humans as a species need to regroup on a genetic level fairly frequently. We also do this in a much more united way with animal life than scientists previously thought.
So, what “catastrophic event” occurred?
We tend to think of a planet-wide catastrophe as something like a meteor that hurtles to the Earth’s surface, wiping out species. But it could have actually been something much subtler.
“Viruses, ice ages, successful new competitors, loss of prey — all these may cause periods when the population of an animal drops sharply,” said Jesse Ausubel, director of the Program for the Human Environment at Rockefeller University. “In these periods, it is easier for a genetic innovation to sweep the population and contribute to the emergence of a new species.”
Some people take this as evidence of intelligent design. It falls under the Noah’s Ark Theory — a way to explain how almost all of Earth’s species showed up around the same time. Whether that is true, it does throw many established evolutionary theories through a loop. Even the scientists who led the study said they were against the idea as they were finding it to be true.
What it means for the future of biological research isn’t yet clear.
But there is clearly a lot of research to be done before we come to a fuller understanding of where we come from.
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