Browse Search Feedback Other Links Home Home The Talk.Origins Archive: Exploring the Creation/Evolution Controversy

Index to Creationist Claims,  edited by Mark Isaak,    Copyright © 2004
Previous Claim: CD001   |   List of Claims   |   Next Claim: CD004

Claim CD002:

Radiometric dating falsely assumes that initial conditions are known, that none of the daughter components are in the mineral initially.


Morris, Henry M., 1974. Scientific Creationism, Green Forest, AR: Master Books, p. 139.


  1. Isochron methods do not assume that the initial parent or daughter concentrations are known. In basic radiometric dating, a parent isotope (call it P) decays to a daughter isotope (D) at a predictable rate. The age can be calculated from the ratio daughter isotope to parent isotope in a sample. However, this assumes that we know how much of the daughter isotope was in the sample initially. (It also assumes that neither isotope entered or left the sample.)

    With isochron dating, we also measure a different isotope of the same element as the daughter (call it D2), and we take measurements of several different minerals that formed at the same time from the same pool of materials. Instead of assuming a known amount of daughter isotope, we only assume that D/D2 is initially the same in all of the samples. Plotting P/D2 on the x axis and D/D2 on the y axis for several different samples gives a line that is initially horizontal. Over time, as P decays to D, the line remains straight, but its slope increases. The age of the sample can be calculated from the slope, and the initial concentration of the daughter element D is given by where the line meets the y axis. If D/D2 is not initially the same in all samples, the data points tend to scatter on the isochron diagram, rather than falling on a straight line.

  2. For some radiometric dating techniques, the assumed initial conditions are reasonable. For example:


Stassen, Chris, 1998. Isochron dating.

Further Reading:

Dalrymple, G. Brent, 1991. The Age of the Earth. Stanford: Stanford University Press.
Previous Claim: CD001   |   List of Claims   |   Next Claim: CD004

created 2003-4-19, modified 2004-9-3