I mean to say that life, all life has a common ancestor, that ancestor was a primitive form of bacteria. Modern bacteria are not privitive and are quite complex. Mammals didn't evolve for almost 3.5 billion years after the first bacteria but yes our very distant ancestors were indeed simple one celled organisms.
Not the same land the same water, conditions on earth 4 billion years ago was much different than today. We can tell this from the geology of rocks left from that time. While things like organic molecules can be made today they are immediately consumed by extant life. The Earth didn't even have free oxygen until around 2 billion years ago.
News species are evolving all around us, it has been observed both in the wild and in the lab. Bacteria are still evolving into new and different bacteria but more complex organisms have a choke hold on ecological niches they can live supressing bacteria from continuing in that direction. Google is your friend...
https://en.wikipedia.org/wiki/Evolution
https://www.livescience.com/474-controversy-evolution-works.html