period 5 osango time line By 2013osangomb Jan 1, 2011 birth of solar system(5 billion years ago) Jan 26, 2011 earth began to form(4600 million years ago) Mar 21, 2011 bacteria diversify(3800 Million years ago) Apr 5, 2011 photosyntheizing bacteria(3700 million years ago) Apr 20, 2011 oldest fossils(3500 years ago) Jul 24, 2011 oxygen appears(2200 millionsyears ago) in the living environment, causing damage to living tissues Nov 1, 2011 90% species go extinct(250 million years ago) Nov 3, 2011 mayor glaciation period begins(800 millions years ago) Nov 5, 2011 protective ozone layer in place(600 millions years ago) Nov 14, 2011 land plants(480 million years ago) Nov 20, 2011 oxygen nears present day levels(400 million years ago) Nov 23, 2011 reptiles(350 million years ago) Dec 4, 2011 pangaea starts(200 millions years ago) Dec 27, 2011 primates(60 millions years ago) Dec 31, 2011 hominds(5.2 million years ago) Dec 31, 2011 modern humans(100,00 years ago)