The entire Earth used to be an ocean a long time ago. Land gradually started to form and grow apart. Life started to take shape from within the waters but couldn’t go on land just yet. Fast forward to millions of years and we see living things hanging out on land for a while. They could now lay eggs on land and be known as reptiles. A couple more million years later combined with some ice ages and meteors, came the dawn of us warm-blooded mammals. We would go on to dominate land with our opposable thumbs evolution gave us.