Many cartoons about evolution show fish - somehow now with legs - climbing up a beach. But the sea creatures that probably climbed that beach first were really arthropods.
Arthropods today are a variety of creatures with chitinous exoskeletons like crustaceans, insects, arachnids, etc. Once on land some 490 million years ago, creatures like them needed to be able to avoid dehydration, have the strength to withstand gravity outside water, deal with temperature changes, and so on. Those exoskeletons helped. It was only later that certain fish made their way to land. Our salty innards recall those early days.
The cartoon pictures of fish climbing a beach, like the line of ape-like to modern humans in other cartoons, are rather misleading in implying progress. After all, big-brained types like us are so smart we really know how to screw up big time. You have to wonder whether those creatures who were first out of the salty oceans might be the last creatures standing. Enrico Fermi had this response as to whether E.T.s are out there. If they are, he wondered, "Where are they?" Well, do you suppose the E.T. equivalent of arthropods - insects, spiders and so on - upon taking over after the big-brained folk wiped themselves off the face of their planets - continued a life in which exploration of space isn't exactly a goal? Where religion, politics, weapons of mass destruction and all that simply go poof, never to exist again?
In the long term, maybe the last living creatures throughout the universe just keep living a good old arthropod life until their various suns go nova. This rather grim alternative cartoon - and of course that's all it is - suggests that life may end, not with fire or ice, but with a scuttle.