In its*4.6 billion years*circling the sun, the Earth has harbored an increasing diversity of life forms:
for the last 3.6*billion*years,*simple cells*(prokaryotes);
for the last 3.4 billion years,*cyanobacteria*performing*photosynthesis;
for the last 2 billion years,*complex cells*(eukaryotes);
for the last 1 billion years,*multicellular life;
for the last 600 million years, simple*animals;
for the last 550 million years,*bilaterians, animals with a front and a back;
for the last 500 million years,*fish*and*proto-amphibians;
for the last 475 million years,*land plants;
for the last 400 million years,*insects*and*seeds;
for the last 360 million years,*amphibians;
for the last 300 million years,*reptiles;
for the last 200 million years,*mammals;
for the last 150 million years,*birds
for the last 130 million years,*flowers;
for the last 60 million years, the*primates,
for the last 20 million years, the family*Hominidae*(great apes);
for the last 2.5 million years, the genus*Homo*(human predecessors);
for the last 200,000 years,*anatomically modern humans.
Timeline of evolutionary history of life - Wikipedia, the free encyclopedia