The internet has never been short on apocalypse scenarios.
From zombie outbreaks to asteroid impacts, people seem fascinated by the idea of how humanity might meet its end.
AI simulations have painted grisly pictures of what global extinction could look like if World War 3 were to break out.
Meanwhile, the so-called 'godfather of AI' issued urgent warnings about the future of artificial intelligence, expressing fears that it could potentially lead to the end of humanity as we know it.
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While many public fears may intensify over time, they're already affecting millions of people globally as AI technology becomes woven into daily life.
Yet according to some experts, things could get far, far worse.
When it comes to imagining catastrophic scenarios, content creator Zack D. Films has made a name for himself by visualising some pretty bleak 'what if' situations.
The YouTuber demonstrated disturbing scenarios like what would happen if you tried surviving on a diet consisting entirely of blood, how something as simple as an infected tooth could potentially kill you, or what would happen if the Earth suddenly stopped spinning (spoiler: it's not pleasant).
Now, he's continued that trend by disturbingly illustrating what would happen if Earth had only one man left alive.
"If you were the only man left alive on Earth and everyone else was female, you would be responsible for repopulating the planet," Zack explained in his situation.
At first glance, this might sound like a scenario that many have fantasised about at some point or other. But the reality, as Zack shows, is far more nightmarish.
"Because all of your children would share half of your DNA, when they had children with each other, that DNA would overlap even more," he said. "And in just a few generations, nearly everyone would be close relatives, meaning the gene pool should shrink dangerously fast."
Science backs this up. When populations become too small and genetically similar, harmful recessive genes that would normally be diluted in a larger gene pool instead get concentrated and expressed.
As a result, he explained that children would be born with severe defects and developmental abnormalities, like 'misshapen skulls and twisted limbs', among other mutations.
"Inside their organs wouldn't develop right and many [children] wouldn't survive," Zack described. "The more generations pass, the worse it gets until the population collapses again."
In other words, even if humanity attempted to rebuild from a single male survivor, the genetic mathematics would doom the effort within just a few generations.
People in the comments section responded with a mix of dark humour and recognition of the bleak scenario.
"New Tip if you are the only guy alive: Don’t be ugly," one user joked.
"Bro never fails to answer the questions we never asked," another replied.
"Zach is turning his midnight thoughts into reality," a third user commented.