It is not difficult to see how such a claim could arise, however.

The shells of live freshwater clams can, and often do, give anomalous radiocarbon results.

However, the reason for this is understood and the problem is restricted to only a few special cases, of which freshwater clams are the best-known example.

These two measures of time will only be the same if all of the assumptions which go into the conventional radiocarbon dating technique are valid.

Comparison of ancient, historically dated artifacts (from Egypt, for example) with their radiocarbon dates has revealed that radiocarbon years and calendar years are not the same even for the last 5,000 calendar years.

Some may have mistaken this to mean that the sample had been dated to 20,000 radiocarbon years.

The second characteristic of the measurement of radiocarbon is that it is easy to contaminate a sample which contains very little radiocarbon with enough radiocarbon from the research environment to give it an apparent radiocarbon age which is much less than its actual radiocarbon age.

It is not correct to state or imply from this evidence that the radiocarbon dating technique is thus shown to be generally invalid.

The problem with freshwater clams arises because these organisms derive the carbon atoms which they use to build their shells from the water in their environment.

Since no reliable historically dated artifacts exist which are older than 5,000 years, it has not been possible to determine the relationship of radiocarbon years to calendar years for objects which yield dates of tens of thousands of radiocarbon years.

Thus, it is possible (and, given the Flood, probable) that materials which give radiocarbon dates of tens of thousands of radiocarbon years could have true ages of many fewer calendar years. The shells of live freshwater clams have been radiocarbon dated in excess of 1600 years old, clearly showing that the radiocarbon dating technique is not valid.

This gives the clam shell an artificially old radiocarbon age.