Is C-14 dating based on this assumption?

Question

i always wondered how they knew how much carbon 14 was present initially. i know it is a simple exponential decay, but in order to solve for time you have to know what the initial number of C-14 is. is it right that there is a ratio of C-12 to C-14 that is said to present in living tissue and that before the industrial revolution that ratio was unchanging? if so, how can that be assumed?

Answer 1

All living organsims produce the same percentage of C-14 in their bodies at all times while they are alive. Once they die, the process stops, and the C-14 begins to decay

C-14 also decays at the exact same rate at all times, we know how old a dead oranism is by measuring the amount of C-14 it has

Answer 2

> if so, how can that be assumed?

Carbon 14 is produced from nitrogen high in the atmosphere by the action of cosmic rays.  It is assumed that this process is constant and has been going on for at least the 60,000 years for which carbon dating is useful.  The other assumption is that carbon "sinks" -- the rate that carbon in the atmosphere is absorbed into the oceans and living tissue -- has been constant.