C-14 is another radioactive isotope that decays to C-12. This isotope is found in all living organisms. Once an organism dies, the C-14 begins to decay. The half-life of C-14, however, is only 5,730 years. Because of its short half-life, the number of C-14 isotopes in a sample is negligible after about 50,000 years, making it impossible to use for dating older samples. C-14 is used often in dating artifacts from humans.