SPOILER WARNING!

Floating predators. Googly-eyed monkeys. Sky cows. Brain matter in tanks. Sentient robots. 

Netflix’s new series Alien Worlds covers them all. Each episode dreams up a fictional planet and the creatures who call it home. When you first see the fantastical critters and colorful plants on each world, you might dismiss the show as pure science fiction, but Alien Worlds is rooted in biology and evolution here on Earth.

What would happen to life on a planet where gravity was twice as strong? How would animals adapt to a planet around a dimmer star? Are we doomed to become a hive mind? Biologist and award-winning science fiction author, Philip Kramer, PhD, and Margaret Reeb, who works at the SETI Institute, have teamed up to break down the series.

Episode 3

Margaret: Episode 3 starts with a description of how we can understand an exoplanet’s atmosphere and whether it has the right mixture of elements to support life. This is super exciting and the James Webb Telescope, which is scheduled to launch in late 2021, will have this capability. As you can imagine, it’s harder to sample the atmosphere’s around smaller, rocky planets where life might exist than larger gas giants. 

Philip: Detecting oxygen would strongly point towards the presence of life. Since oxygen is so reactive, it would most likely exist in combination with other atoms like carbon, hydrogen, or even oxidized metals. For it to be free of those, it likely indicates an active process like photosynthesis. The planet in this episode is chock-full of oxygen.

Eden

Margaret: Eden, our next fictional planet, has 31% oxygen, which is ten percent more than on Earth presently. Eden gets all this oxygen from the epic plant life on its surface–which is fueled by its two stars and an axial tilt that provides a lot of light. Also, a two-star system would make me nervous — it could get unstable fast. All the life we see could be on borrowed time. 

Philip: This planet is definitely more lush and verdant than the others we’ve seen so far. The creators took a lot of time filling this world, though they focus mainly on the relationship between three lifeforms. 

Grazers

Philip: The first life we see, aside from the tree and plant life responsible for the photosynthesis, are Grazer. 

Margaret: I did not like their faces. Also, their eyes looked wooden. The design made me wonder what material they were. 

Philip: Yeah. With such narrow pupils, I wonder how any light gets in. Unless it is a compound eye like those of an insect. Now that you mention it, the rest of its features are reminiscent of a moth, from the antennae to the fuzzy coat. I anticipated seeing both common and new sensory organs on Eden. Humans have 21, so it stands to reason that other lifeforms would adapt their own subset of these or more that are specific to their environment.

Margaret: Also, let’s just talk about their (ridiculous) reproductive system. The grazers have to be on the constant lookout for the predators in the trees, which is why they don’t actually have sex. They release worm/caterpillar things that slither along until they find another worm/caterpillar to fuse with. I hated this. Wouldn’t these worm/caterpillars be extremely vulnerable?  

Philip: That was some weird stuff and incredibly complex. Then again, the life cycle of both parasites and moths from which I imagine these were inspired, are also pretty complex. The head of the worm is the textbook image of a tapeworm’s scolex. It’s been over ten years since my last parasitology course, but that’s something you never forget. 

Margaret: Come to think of it, they do look like moths! And let’s talk about how the fused worms turned cocoon lassos itself into the tree branches WHERE THE PREDATORS LIVE. Wouldn’t it be better to just stay as a cocoon on the ground? Can you tell I don’t think this is very believable? Maybe I need to enroll in a parasitology course to get on board. 

Predator

Margaret: So these guys look like monkeys but with a secret weapon– a stretchy pair of arms that shoots out of their armpits. I had seen the trailer so I knew this was coming but my boyfriend laughed out loud. 

Philip: I’d be curious to hear how the creators justified this one. An articulated and stretchy arm is counterintuitive. In order to articulate, you have to have some sort of skeleton and joint and those are notoriously not stretchy. This does appear to be the most anthropomorphized species we’ve seen so far. Where does SETI stand on the question of whether aliens will have human-like characteristics?

Margaret: The SETI field is so varied it’s hard to say, but I think there is a universal drive to know what’s out there and how similar it might be to life on Earth. I think the field is constantly challenging itself to think outside of the box and question whether our approach to the search for extraterrestrial life is too human-centric. Put another way, could we miss signs of life on another world because we are only looking for things that look and sound like us?

Philip: Good point. It would be very unlikely for them to have a similar evolutionary history. But there is a strong rationale for why they might look somewhat similar to us. They’ve brought it up in this series before. Those things that are inherently useful evolve independently over and over again, like eyes and venom. I think the symmetry of the face, the arrangement of eyes and ears, nose and mouth, are all there for maximum coverage, height for surveying, and proximity to the brain. The proportions of the human body may prove advantageous for aliens too, with the fulcrum of our elbow and knees less useful for raw power but running and throwing speed. If we ever encounter an intelligent species that needed many of these same advantages, I think they might look humanoid. Though I highly doubt it will be so subtle as a small brow ridge, pointy ears, and green skin.

Margaret: Yes, it would be interesting to see if large brains evolve on other planets. Our brains have given us the ability to organize and take over the planet but they require a lot of resources. In fact, chimpanzees are so much stronger than us even though we’re closely related because they use so much of their energy on muscle mass. We, in turn, use it on our brains. 

Philip: Overall, I think these predators look a bit too human, but they seem to fit in with their environment very well. Especially how they interacted with the other creatures sharing the forest. 

Margaret: Let’s talk about this because if I was critical before, buckle up for what I think about these gross pod things.

Fungi

Philip: If anything, it’s the fungi the grazers eat which have the more complex life cycle. The spores from the orange fruits that appear late in the season infect the grazers, removes their sense of fear, and makes them more prone to predation. The toxins the spores produce in the grazer then kills the predator, and fungi sprout from its decomposing corpse. 

Margaret: I’m going to try not to blow a fuse. You would think evolution would have selected against this. At some point the grazers would have learned not to eat the orange fruit and the predators would have learned not to eat the prey with the glassy-eyed stare. BUT MAYBE THEIR GENES ARE TOO DUMB.

Philip: It reminds me of a newly discovered parasite on Earth which causes ants to swell and look like berries. Birds eat them, and their droppings are then eaten by ants, completing the cycle. Like these fungi, the fungus Ophiocordyceps unilateralis has some mind altering properties in ants, releasing a specific cocktail of metabolites into the host brain to cause it to seek out an environment more suitable for the fungus. The fungus then infects the mandibular muscles, causing the ant to latch on to a leaf until it dies. Only then will it create a fruiting body and release its spores. These are just two examples of some really complex life cycles right here on Earth. The fungi in this episode is pretty simple by comparison.

Margaret: Also, the fungi kill all the grazers except for the ones in the cocoons. This seemed ridiculous to me. There is no way this ecosystem would last if a key part of it dies out leaving only the vulnerable young. I would have been more okay with this if some of the grazers hibernated. I just don’t understand how this set up could have evolved when it’s so prime to collapse. 

Philip: If they are as dumb and prolific as moths, maybe they don’t need much care. I think it all depends on how developed they are when they emerge from the cocoon. All we get is a shot of a slimy snot ball falling to the ground. Maybe they come out fully developed and ready to eat all the early nontoxic fruit of the fungi. One thing going for this episode, it got me thinking a lot about ecosystems and how every lifeform is dependent on another. As Mufasa would say, everything exists together in a delicate balance.

Margaret: It’s the circle, the circle of LIFEEEEEEEEE!