The bone has long ago rotted away and has been replaced by rock.If you've found carbon to date in a fossil, it's a modern contaminant, there's no bone there, it's rock!Radiocarbon dating can’t tell the difference between wood that was cut and immediately used for the spear, and wood that was cut years before being re-used for that purpose.Nor can it tell if a much older spearhead was attached to a brand-new shaft.Of course, there are many problems with such dating methods, such as parent or daughter substances entering or leaving the rock, as well as daughter product being present at the beginning.Here I want to concentrate on another source of error, namely, processes that take place within magma chambers.These long time periods are computed by measuring the ratio of daughter to parent substance in a rock and inferring an age based on this ratio.This age is computed under the assumption that the parent substance (say, uranium) gradually decays to the daughter substance (say, lead), so the higher the ratio of lead to uranium, the older the rock must be.
Radiometric dating is largely done on rock that has formed from solidified lava.
Most scientists today believe that life has existed on the earth for billions of years.
This belief in long ages for the earth and the existence of life is derived largely from radiometric dating.
I'm certain there are times when particular readings were wrong and had to be corrected because of contamination or something. Another flaw is it doesn't work well on things that contain no carbon.
Because radioactive decay is an exponential process, using it to date very young or very old (relative to the half life of the isotope) is bound to give wildly inaccurate results.