Interactive evolution: simulating an ecosystem

Games company Slug Disco are releasing a new game that models evolution underwater
16 March 2021

Interview with 

Tom Johnson, Slug Disco


An underwater view of the ocean surface.


A new video game simulation is being published by a company called Slug Disco. It models the evolution of life in a realistic underwater world. You put basic starting creatures into the water, and then create the environment in which they will live. You then watch as they evolve and adapt to their environment, and to each other, just as Darwin described. It’s called Ecosystem, and the Naked Gaming Podcast’s Chris Berrow caught up with its creator, Tom Johnson...

Tom - It's kind of inspired by some research that was done in the nineties at MIT, by a guy named Karl Sims, and he was working with virtual evolution. So the idea is that you have these creatures that are actually a bunch of boxes joined together, basically. And they have virtual brains that are basically pipeline computers. So they take in visual input, auditory input, stuff like that. They do a bunch of processes. And then as an output, they apply torques at all their various joints. So they kind of move around just like we do. So unlike a normal game, the creatures aren't necessarily playing like an animation that an artist made, they're actually contracting joints at each joint that they have. And so the idea is that if you take a bunch of these creatures, just like totally random ones, with random brains and random bodies, and you throw them in the ocean, most of them will just kind of flail around, right. They'll just be moving their hands and arms, or their limbs, and not going anywhere, but a few will probably get a little bit. And if you let the ones that move the furthest have the most children, then after enough generations, you will actually have creatures that can actually swim. So in that sense, it's like a true evolution game, because the physiology is driven by the function. And so the premise of the game is basically that you shaped this environment and then, you sort of throw in these creatures and they adapt to all the different niches that you create

Chris B - How do you model something like that? Because I know that there are existing models for evolution, but how did you actually design that into a game context? Because that strikes me as probably the most difficult thing.

Tom - Yeah. It took a lot of work. And in fact, when I first started, it would actually take a full day just to get an evolution, just to get a creature that can kind of swim. It was a very sort of experimental process, because it doesn't map quite cleanly to an existing game. There's not some well-established tradition that I could kind of follow in, and copy, you know? So to some extent there's a big element of creativity to it, that you kind of have this fish tank, except that the fish are morphing to your tank.

Chris B - What are some of the other factors that are at play here?

Tom - There's a couple of other ones. One that I did recently was a creature vision system. So in addition to their physical body shape, their skin colouration and pattern, and stuff like that also evolves. And it's sort of encoded in their DNA. And so when creatures are preying on each other, they have a vision simulation. So in order to actually see a creature, if it's green against the green background, it's harder to make that out. Like the better it fits to that, the harder that creature is to see, because for example, a bunch of foragers that have no predators anywhere don't actually really need camouflage. And so they may end up more like the, you know, the birds of paradise, right? Like the classic ones with the incredibly ornate, because it's better for mating, right? If you have the best shiniest, whereas if there's a bunch of huge sharks swimming around looking for you, then suddenly you don't want to be the most ornate, beautiful purple fish, but you want to be the one that looks just like the dirt.

Chris B - I'm presuming that if you were to in real life, create an environment, that exactly the same thing wouldn't happen every time. Like, you know, you might suddenly find that actually, you know, some creatures with shiny wings or whatever would start to become very prominent. But then if you ran it again in real life, you might find that actually camouflage became the way to go just for no reason, just because that's sometimes what happens with evolution. Does that happen in the game as well? Or is it very much if you were to chuck the same thing in the same environment, it happens the same way.

Tom - There's quite a bit of variation, just because of random features and even how creatures are reacting as part of their environment is the other creatures, in a sense. There's a decent chance, at least if you set the pressures just right, that you could probably get a camouflage to statistically occur more frequently. One of the main goals for the game was that I wanted to sort of make sure that it could actually reproduce, as much as I could, the amount of variety that you see in life. So I think I would have been a little disappointed if like, you always got the same handful of things. And for that reason, they often tend to come out looking like little monsters. You get a lot of very alien looking things. But there's probably a decent chance that if you threw some microbes into the ocean and Earth, you may not necessarily get fish again. You know, you might not get things that look exactly like the fish that we're used to.


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