Carbon dating is only good for up to 60,000 years because the material it measures, C-14, decays into other materials with a half life of just over 5000 years. By the time you get past 60K, there is so little remaining that its not measurable against background noise.<quoted text>
At what point does carbon dating break down?
And how would you really know if it did or didn't?
For older materials, other decaying isotopes are used with half lives from thousands of years to several billion years. However, only carbon-14 is actually IN the specimen. For the older datings, they date the rocks around and above the fossil, and they can only be certain types of rock too.