In the recently released film Arrival, Amy Adams plays a linguist charged with figuring out how to communicate with aliens who have landed on Earth. Visually, the aliens—called heptapods—are a testament to masterful movie magic: Everything from their subtle, fluid movements to the dense atmosphere in which they breathe fits with our idea of biological possibility. These otherworldly life forms seem truly feasible, even real.

But perhaps what makes the heptapods in Arrival most believable is that they are not all that alien to begin with. From their body shape to their tentacles to their ability to squirt an ink of sorts, heptapods bear a strong resemblance to Earth’s most alien intelligent life: cephalopods (squid and octopus).

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