I spend an inordinate amount of time thinking about the apocalypse, and I’m starting to think it’s genetic. Humans have been imagining creative renditions of the end of the world for thousands of years.

Christianity, Judaism and Islam each tell their own version of the Day of Judgment. Pagan Scandinavians prophesied Ragnarok. The Mexica of Central America butchered human sacrifices beyond count — sending severed heads rolling down the steps of their pyramids, lifting up cut-out hearts to the heavens — all to delay the end of days.

This illustration from the Aztec Codices depicts the Spanish interpretation of a Mexica sacrificial ritual. (Source: Wikimedia Commons)

However — and correct me if I’m wrong here — the world hasn’t ended yet. For the life of me, I just don’t remember the apocalypse.

Well, maybe I do, in a way. In the way a monarch butterfly remembers the route from Canada to Mexico, despite having never made the flight. In the way a hatchling sea turtle understands the urgency of its race from the beach to the tide, despite having just been born.

I have forever been fascinated by the primordial, whispering voice we call instinct. It’s a relatively unexplored field of research, so all we really have are working hypotheses about how instinct actually works (e.g. Carl Jung’s model of the collective unconscious) — but recently, neuroscientists at Emory University have taken some important steps to explain the mechanics of this profound, intrinsic drive.

The researchers conducted trials of olfactory fear conditioning on mice — training them to be afraid of a specific scent via fear-potentiated startle (i.e. scaring the bejesus out of the mice with sound and electricity when they’re in the presence of acetophenone, an aromatic keynote) — in order to determine the effect on their offspring’s behavior and neurophysiology.

What they observed was that the offspring of these mice — who were conceived after the fear-conditioning trials — were much more sensitive to the scent of acetophenone, despite having never encountered the chemical during their lifetimes. The genetic sequences responsible for coding the region of the brain that interpret this type of sensory input had been augmented by the trauma experienced by their parents — a phenomenon referred to today as transgenerational epigenetic inheritance.

Principle investigators Brian Dias and Kerry Ressler of the Department of Psychiatry and Behavioral Sciences at Emory wrote in their Nature Neuroscience report, “Such information transfer would be an efficient way for parents to ‘inform’ their offspring about the importance of specific environmental features that they are likely to encounter in their future environments.”

If this type of instinctual understanding can be passed between as few as two or three generations, one can imagine the scale of genetic memory that could be passed over 4 billion years of biological evolution, beginning with ancestors common to you, me, the monarch butterfly, the sea turtle, your neighbor’s pug and the succulent on my coffee table — back through deep time to alien organisms so incomparable to life on Earth today.

Tracing these intersecting lines of biological heritage through Earth’s rock record, paleontologists have revealed evidence for no fewer than five mass extinction events — cataclysmic episodes that either swiftly obliterated or slowly withered away most life on Earth — true apocalypses.

Violent flood volcanism (which may have resulted in the Triassic-Jurassic extinction) devastated the landscape and blacked the sky with dust and ash, warranting the Dantean description of a “lake of fire.” The destructive force of extraterrestrial impacts (like that which left its scar on the Yucatán Peninsula, the prime suspect of the Cretaceous-Paleogene extinction) would not have been unlike the Mesoamerican myth of the third apocalypse in the Five Suns cycle, when they believed the world ended in a “rain of fire.”

Pāhoehoe and Aa flows at Hawaii.jpg
Pāhoehoe and Aa flows at Hawaii provide a small-scale model of the kind of massive floods associated with exponentially larger, more violent eruptions that would have led to cataclysmic changes in the environment that wiped out the majority of life on Earth. (Source: Wikimedia Commons)

While humans were hundreds of millions of years from stepping onto the evolutionary stage, every living thing on Earth today is descended from organisms that survived these apocalyptic events — one of which obliterated 90 percent of life on the planet. If the lab mice at Emory became wary around a scent that harbingered trauma to their parents, perhaps being part of a family tree that weathered five planetary-scale cataclysms has left a more profound mark on our instincts.

Perhaps we have “experience” with the end of the world in the same way that a newborn giraffe seems to have experience running when it’s only a few hours old. Maybe our species’ fascination with the apocalypse is more than an irrational fear or an artistic expression — but rather a cultural articulation of life’s remarkable endurance and blind ingenuity.

I hope I’m right. If I’m not, I can’t cite the 4-billion-year-old fossils encased in ancient hydrothermal vents to explain why I end every day with a hot bubble bath. I just have to admit that I take bubble baths.

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