Final answer:
Radiocarbon dating uses the decay of carbon-14 to estimate the age of organic material up to about 50,000 years old by measuring the carbon-14/carbon-12 ratio in the remains and comparing it to the atmosphere's ratio.
Step-by-step explanation:
Studies of carbon isotopes, specifically carbon-14 (or 14C), are used to detect the presence of past biological activity in rocks through the process known as radiocarbon dating or carbon dating. The unstable isotope 14C is constantly created in Earth's atmosphere and is taken up by living organisms through respiration, leading to a steady level of 14C in their bodies while alive. When organisms die, they stop replenishing their 14C and it begins to decay to nitrogen-14 (14N), with a known half-life of about 5,730 years.
By measuring the carbon-14/carbon-12 ratio in the remains and comparing it to the current atmosphere's ratio, scientists can determine how many half-lives have passed and, consequently, estimate the time since the organism's death up to about 50,000 years ago. This is a crucial tool in studying the past ecosystems and the existence of previous life forms.