What property of radioactive elements makes them useful for determining absolute age

Radiogenic isotopes.

Explanation:

Dating is a process by which archaeologists get to know the absolute or relative age of a past objects. Absolute dating deals with the process of determining  the absolute age of the  element.  During dating of objects, or during the radiometric dating if we know the half-life of the element, it will be easy to know the age of that object by determining the decay rate of the isotopes.  

answer; incomplete dominance;