 So, the fossil record also gives us and just living critters. I mean, there's lots of ways that we're going to look at this. But another piece of evidence that speciation has said, that we're related to each other. That we're related to other critters. And the more related we are, the more similarities we have, more evidence of that is this concept called homologous structures. And does that, what does that do for you? Does that make you go, hey, I know what homologous structures are because I love homologous chromosomes. And homologous chromosomes are very similar to each other. And so you would expect homologous structures to be very similar to each other. And the fact is that they are. They're, check out these fossils, like this is going to blow your brain. Here is a cladogram. You've seen something like this before. You can see who's most closely related to whom. We have a ray fin fish, which is like a trout. That isn't a trout, but it's like, okay, that looks like a tuna or something like that. And ray fin fish have fins. They don't have like arms. And their fins don't, they've got like, what are they, like little rays, that might be why they're called ray fin fish. Because they've got all these rays that go out and let them swim, but they're not fingers. And they don't have arms. But there's a fish called a lung fish. And that, okay, it looks like we don't have lung fish body parts. But these are fossils that they have found. Look at this thing. The unimpernape has inside the fin. And that's a fin. They have these bones that are homologous structures to a living tetrapod, which has a humerus, that's a humerus, an ulna and a radius in your forearm, all your wrist bones, your metacarpals and your phalanges. And that pattern, look, here they are. Your phalanges, your ulna and your radius are a humerus, one big bone, two long bones, a whole bunch of little blobby bones, and then fingers. These guys have it, finger bones, blobby bones, two forearm bones, and an arm bone. Fingers, blobby bones, two forearm bones, and a humerus, a one long arm bone. And then look at this, even this guy, look at this guy, that's tiktolic. That's like the first one that came out of the water. Like, if you have this setup going on, you're not going to floppy flap your fingers. Like, you can walk on those things. You've got bones in there to support those fins, which is a step toward having a limb. Did you understand what I just said? Because I started going backwards and we kind of had to know what our anatomy is. Like, living tetrapods are living critters that have four legs, and we're included in that even though we stand up on two of them and use the other two for hi-hi now. So this right here is actually evidence of macroevolution, of speciation. It's evidence of critters moving from the ocean onto land. I think I have another visual, here's another visual. Now, this one is all living creatures. So these are living tetrapods. The other one was fossil creatures, which is really cool. But this one is, you can see that they've color-coded the bones so that you can visualize which ones are homologous structures. It's the same bone. It's been slightly modified for a different function. The structure has been slightly modified for a different function. But look, Gorilla Dog Pound looks just like us. A bat, look at those long fingers. And this is a wing, but those bones are all still in there. Same pattern, long bone, two long bones, lots of blobby bones and fingers. Fingers, blobby bones, two long bones and one long bone. And there's a whale, that's its bones inside, it's fin. I mean, wow, that's amazing. We could look at a bird as well and we would see the exact same similar pattern because it's the exact same similar pattern. Now, homologous structures indicate relatedness. It's really important that that works in your brain. If a structure is homologous, it indicates that these creatures are related to each other. The bones are homologous. There's another kind of structure and it's called an analogous structure. And let's talk about that one next.