Hello I am new to the field. Can someon answere, i cannot find the answere in books. if life 3.8 billion years ago could form in very harsh conditions. then whay cannot it happen again today. whay cannot it have been happening all the time for almost 4 billion years. i have read that all animals have a cummon ancestor and all plants have a cummon ancestor too, and there also is a cummon ancestor for both plants and animals, and it all leads back to single cell organism. now if we can trace back a cummon ancestor for all living or growing things on earth, then where are the living things that came later. Does this mean that in 4 billion years there have been only one spark of life that led to complete diversity of life... and guess what, it happened right next day after earth stopped being bombarded by asteroids. hmm what a coincidence. 1. WHERE ARE ANIMALS (OR SOMETHING ELSE ALIVE) THAT APEARED AFTER THE EARTH WAS ALLREADY INHABITED??? 2. have this aspect been discussed in science world? 3. If we want to know so bad how life on earth got started, cannot we just observ it starting today?