They prey on their own kind. Some might call it cannibalism, but it’s the only way they can survive. Indeed, the zombie apocalypse is here.

Sort of.

So-called “zombies” exist throughout nature, but unlike their fictional counterparts, these zombies serve a good purpose.

For example, our very own galaxy has gobbled up smaller galaxies for over ten billion years. Astronomer Jeff Zweerink tells me that this regular diet of galactic food keeps star formation at a steady pace. Continual star formation might not seem like a big deal, as though non-continual star formation just means fewer objects to spot in the night sky. But, as Jeff puts it, “a galaxy must form multiple generations of stars” in order to host life. “On the other hand,” he continues, “a collision with a galaxy that was too large would have disrupted the MWG’s [Milky Way Galaxy’s] spiral structure and led to conditions hostile to life.”

Collisions with the just-right size galaxies affect our galaxy’s structure and add energy to the outer part of the Milky Way’s disk. According to Jeff, these cannibalistic collisions remain frequent throughout cosmic history, and yet they’re not so frequent as to disrupt Earth or any other planet in our solar system. That’s comforting.

Astronomers aren’t the only ones who get to “see” nature’s zombies in action. They can also be found much closer to home, too. Biochemist Fazale Rana explains a process called phagocytosis.

Phagocytosis is the process by which cells will eat solid material that can include other cells. It’s a way for cells to gain nutrients but it’s a critical part of the body’s defense mechanism so that when infectious agents like bacteria invade the organism the immune system unleashes cells that will recognize the bacteria’s foreign materials and then will consume them through phagocytosis.

It might seem like a stretch to refer to these cells as zombies, but Fuz assures me, “If one would like to call them zombie cells, one most certainly can.” Sounds good to me.

So if a gruesome zombie shambles to your front door looking for treats this Halloween, remember that zombies—at least those found in nature—are nothing to fear. Whether it’s zombie galaxies or cells, even the odd features found in nature point to universe that was fine-tuned to support life. Now there’s something to sink your teeth into.

–Sandra

Resources:

For more about “zombie” galaxies, check out these articles by Jeff Zweerink:

“Planet from Another Galaxy Discovered”

“Steady Diet of Dwarf Galaxies Maintains Milky Way Spirals”

“Milky Way Gobbled Gobs of Galaxies”

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