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Explaining Hox Genes: The Science Behind Annihilation
Annihilation's Shimmer messes with Hox genes, the genes responsible for giving your body parts their identities.
In Alex Garland’s psychedelic sci-fi horror Annihilation (streaming now on Peacock), a small group of explorers from a secretive research outpost enter an alien environment known as The Shimmer, where the rules of biology splinter. There, they find an ecosystem made of flora and fauna forever fragmenting on a genetic scale. Deer have plants sprouting from their antlers, alligators turn pale and grow teeth in rows stretching down their throats, and skull-faced bears learn to mimic human speech.
The simple explanation for what’s happening inside The Shimmer comes down to the influence of an alien entity. Whether it’s malevolent or simply acting on survival instinct is unclear, but its twisted impact on the surrounding environment is broadly on display. The more complicated explanation involves the manipulation of a small but important part of DNA, known as Hox genes.
For More on DNA:
The Ways The Croods (Neanderthals and Other Ancient Humans) Are Alive in Us Today
This Tiny Island Fern Has the Largest Known Genome with 50 Times More DNA Than Humans
Can We Save Living Species by Recovering Extinct Genomes from Dire Wolves and Giant Sloths?
How Hox Genes Determine the Body Layout of Plants, Animals, and You
Inside The Shimmer, DNA, mutation, and evolution go hog wild, resulting in some truly alien creatures built on the blueprints of ordinary, Earthly plants and animals. It comes to a head when Lena (Natalie Portman) and the rest of the crew encounter a set of plants taking the shape of humans. There’s no denying that they are forming the silhouettes of people, and the eerie uncertainty underlying that behavior is spine-tingling. Are they plants simply mimicking a human shape or are they the mutated remains of a previous expedition? Whatever their origin, Tessa Thompson’s character, Josie, speculates that changes in the Hox genes are responsible.
In the real world, Hox genes play a crucial role in the construction of the body, and meddling with them ends with interesting and often horrifying results. If your DNA is the detailed blueprint for your entire body, the Hox genes are the foundation and the framing. They lay out the body plan, telling everything where it should be and what it should be. It’s how your body knows where to put the head, trunks, arms, legs, eyes, fingers, toes, and everything else. The Hox genes lay out the thumbnail sketch of your body, then other genes come in to fill in the details.
If an alien entity (or laboratory scientists) tinker with the Hox genes, they can get plants and animals to do all kinds of weird things, some of which is the stuff of horror movies. Fruit flies, for example, begin life as segmented larvae. As they develop, the Hox genes tell the body not only how many segments to make, but what each segment should do as it grows.
In a normal fruit fly, segments in the middle grow legs and wings, while segments at the front grow eyes, antennae, and mouthparts. If there are mutations in the Hox genes, however, then fruit flies grow appendages in all the wrong places. Scientists have observed fruit flies, either through natural or directed mutation, growing only two sets of legs and an extra pair of wings, or growing legs out of their faces, where mouthparts or antennae should be.
The situation is a little different in vertebrates, like us, but we are still segmented creatures laid out stem to stern. Hox genes tell our vertebrae if they should grow ribs or not, they tell your arms and legs where they should go and whether to be an arm or a leg. In lab experiments with mice, mutations in the Hox genes can cause distinct changes in limb formation. In humans, limb deformity has also been associated with differences in Hox genes.
There’s still a lot we don’t know about Hox genes and how they express themselves in our bodies, but one thing is certain: If you encounter a biome that turns your Hox genes on and off, swapping them with other organisms, run!
Visit The Shimmer from the safety of the sofa in Annihilation, streaming now on Peacock.
