How do scientists use radioactive decay to date fossils and artifacts?

Scientists use radioactive decay to date fossils and artifacts through a process called carbon dating it measures the amount of carbon still left in a dead object. The less carbon that exists, the longer that animal or plant as been dead.

Many archeologists and anthropologists disagree with dr. thorne's view.  thorne strongly believes that what many calls "homo erectus"  was in fact  homo sapiens,  and that they migrated out of africa almost 2 million years ago and dispersed throughout europe and asia. that's way different  from what scientists have always believed about the evolution of the species.

Are their choices to the question?