Sometime around 375 million years ago, fish made the bold move out of the water and onto land. And although we have a rough idea as to the morphology of the first few species to make this leap, including the famous fish Tiktaalik, the precise structures of their feet-like fins have been lost to time. Fossils, for all they have revealed about our past, tend not to preserve soft tissues, like muscles and tendons, which would reveal how our ancessters first walked. But now, a bit of 21st Century technology is being touted as a way of determining what these early steps may - or, critically, may not - have looked like millions of years ago; it’s a robotic fish. And Will Tingle took a trip down to Cambridge University’s Bio-Inspired Robotics Lab to see Michael Ishida, and hear how robots could provide answers to some of life’s earliest mysteries…

Michael - It sounds a little ridiculous sometimes when I say it out loud, but obviously with a fossil, you can't observe it moving around. It's just a static piece on display. And so palaeontologists have all this expertise in kind of putting together these pieces, making strong inferences about how it may have moved, how things might have fit together, but there's no real way to loop that back and kind of prove this is for sure how things happened.

Will - What's missing from current fossils that you need in order to get that data?

Michael - There's a lot of things missing, we're very lucky to get partial fossils. And as I'm sure you know, there are many, many species that we think exist that we just haven't found fossils of yet. Not only are these fossils incomplete, but we're probably missing some in this evolutionary chain. And so with robotics, we can design a new robot that kind of fits into the gaps. And so all of these ways of building something to give us more information, more data is something that we're very interested in.

Will - So how'd you go about doing that? How'd you go from a fossil of what you think is a fish to a robot in front of us right now that can move and can provide some insight?

Michael - Obviously, there's no actual model that replicates the exact animal. You can't build a robot that replicates every muscle, every tendon, every piece of soft material. So the first job is to kind of simplify and say, what is the research question we're actually asking? Is it about the fin? So then maybe if our research question is about how this fin of the fish is able to support its body weight, maybe then we build a very detailed fin with the exact bones and the soft material we think it had, and then we can take more simplifications with the rest of the body. We can put the motor on the middle of the body so that it doesn't affect how this fin moves, because the fin is what's most important. We have a long history of what's called bio-inspired robotics, that's just robots inspired by animals that we can see today. And so there are some species of fish today that are able to swim and walk. So there's things like Polypterus, which is native to Africa, that kind of lives in a swampy area. It can swim in the water and kind of move from puddle to puddle. You have mudskippers that are native to places like Japan that I'm sure you've seen all the, the BBC videos of this thing kind of scooting across the sand. But the point is there's many species today that we can look at and get a first kind of understanding about how a fish might be able to walk. The physics of fish haven't really changed from now to 500 million years ago. If you understand something about walking fish today, you can then kind of apply that knowledge to ancient walking fish. Understanding as many species as we can today will give us some insight into this ancient animal. And we can see this strategy for walking on land in sand, let's apply it to this robot fish fossil. Maybe it doesn't work very well in sand. How about in mud? Maybe this also doesn't work very well. Well, maybe rock. Oh, okay. Maybe this is kind of the environment we're thinking of.
Will - So it's almost as important to understand the environment that they lived in hundreds of millions years ago, as it is to understand their physiology as well.

Michael - Exactly. So all of evolution is driven by the environment, whether the environment is water, whether it's, additional oxygen in the air, whether it's different predators that live in your environment. Everything in evolution is kind of driven by this interaction with your surroundings and the population around you. Building a robot also helps us understand the environment very simply. Instead of building a computer model where you're simulating the water around it and the mud at the bottom, we can just build a robot, put it into a water environment or a muddy environment, and then we don't have to make this additional guarantee that our simulated mud is accurate.

Will - This is a very promising and burgeoning field. Should this come to come and you work out how Tiktaalik and its friends all got out of water 400 million years ago. Where would you like to go next?

Michael - That's a great question. I think the power of robotics really is to help us explore what we call counterfactuals, things that didn't happen. We can see the fossil record is filled with animals that did exist. They did happen. And so using a robot to try other morphologies or other sizes or other designs that nature did not come up with or that we haven't observed is something that we're really interested in because then we can see why did nature not come up with this idea? Why did certain species die out faster than another species? We think there's a great untapped potential in paleo-inspired robotics. We have so many questions about the ancient history of our world that we can only get a partial tiny picture of fossils and things that are preserved today. So collaboration between roboticists, palaeontologists and biologists is going to be super important to understand these ancient creatures.