How would you account for the fact that fossils of fish are not present in the older layers of rock?

The fish did not yet exist when the old layers of rocks were deposited. In fact, animals with hard parts did not evolve until about 600 million years ago, which is only about 13% of the 4.5 billion year age of the Earth. Multicellular animals without hard parts left tracks in older sediments, but had no fossilize-able body parts.

Explanation:

nucleic acid molecules are incredibly complex, containing the code that guarantees the four different nucleotide units comprise dna, the nucleic acid of interest to the genealogist. and one of four nitrogen-containing molecules called nucleotides