As time progressed each would begin to acquire its slower modern-day stable half-life, but would they all acquire these stable rates in a uniformity which would keep them all in synchrony? If they did, all would give the same ages, you are right.Each would probably arrive at equilibrium at different times.Consequently organisms living there dated by C14 give ages much older than their true age.A lake Bonney seal known to have died only a few weeks before was carbon dated.What would happen if a dinosaur bone were carbon dated?- At Oak Ridge National Laboratory, Scientists dated dinosaur bones using the Carbon dating method.The results can be as much as 150 million years different from each other! They then pick the date they like best, based upon their preconceived notion of how old their theory says the fossil should be .So they start with the assumption that dinosaurs lived millions of years ago, then manipulate the results until they agree with their conclusion. So why is it that if the date doesn't fit the theory, they change the facts?
A great book on the flaws of dating methods is "Radioisotopes and the age of the earth" (edited by Larry Vardiman, Andrew Snelling, Eugene F. Published by Institute for Creation Research; December 2000) Dating methods are based on 3 unprovable and questionable assumptions: 1) That the rate of decay has been constant throughout time. That the isotope abundances in the specimen dated have not been altered during its history by addition or removal of either parent or daughter isotopes 3) That when the rock first formed it contained a known amount of daughter material ("Radioisotopes and the age of the earth" pg v) We must recognize that past processes may not be occurring at all today, and that some may have occurred at rates and intensities far different from similar processes today.When each of these elements, uranium, potassium, radium etc.were switched on, it would only be natural for them to behave according to their individual properties, eventually acquiring stable half-lives of decay, at different rates.Many people are under the false impression that carbon dating proves that dinosaurs and other extinct animals lived millions of years ago.What many do not realize is that carbon dating is not used to date dinosaurs. Carbon dating is only accurate back a few thousand years.Look at biological breakdown everywhere, it proceeds at different rates.