This means after 5730 years, there will only be half as much C14 as when the organism died. For practical reality, however, this doesn't always work. Researchers testing the shell of a live clam showed this live clam had been dead for 300 years. Dried up seal- carcasses only thirty years old have tested as old as 4600 years. Fresh carcasses often date as old as 1300 years.
Radiocarbon dating makes several assumptions.
If any of these is wrong, the results can be in error. This method assumes the C14 is absorbed by the organism at the same rate as the C12 from the environment. This is not always true. Some organisms have some type of internal metabolism that can reject the C14 more effectively than the C12. At death, then, these organisms have abnormally low C14 levels and appear much older than they really are.