The changes involved in adapting a generic mammalian template into a whale are certainly not all simple, independent, single-letter changes.
A bottleneck of two, or a first pair at our origin older than 500,000 years, is possible.
In order for evolution to have occurred as the orthodox theory describes, the intricate embryonic development stages of species must have evolved.
Dubious procedures like these would be unthinkable in other natural sciences, such as physics.
Organisms display similarities of sequence, form, or life history that cannot be accounted for by their family tree.