At the start of the Precambrian a human was just born can cant talk or walk
At the end of the Precambrian a Human is in his late 50s. Most of earth's history has happened. Precambrian lasted for 4100 million years and the human has grown up, gotten a job, married and retired.
We are now in the Paleozoic Era and the human is in his 60s. Reptiles, fish, sharks, first forests, insects and many more start to spring up during this age. At the end of his 60s a mass extinction happens.
The man is now in his 70s and the it is now the Mesozoic Era. the Earliest birds, dinosaurs and mammals start to spring up. The man is probably a grandfather now and is preparing for his death.
The man is now in his 80s and has lived a full life.We are now in the Cenozoic Era, during this time early modern group of mammals appear. Early Grasses and Humans start to appear.
The man has died and we are now in the Holocene Epoch and we are now starting human history. It is 0 million years ago and the man has lived his life.