Of course, Cosmic Ancestry does not claim to have the complete explanation for introns either. But it does suggest new ways to approach them. Introns make more sense if evolution is a constructive process involving the systematic assembly of blocks of instructions imported from outside the cell. Perhaps a gene can be imported whole, but must be disassembled and reassembled elsewhere within the genome by the processes of transposition and site-specific recombination. The fragmented aspect of genes with introns is reminiscent of the way computer code may become physically fragmented after it has been retrieved from the hard drive and returned.
Many genes are very similar from the lowest to the highest eukaryotic animals.
Often the main difference among the different creatures' versions of the same gene is that they contain more introns as you go up the evolutionary hierarchy of organization. For quite a few genes, the version possessed by lower eukaryotes such as yeast has no introns, while the versions in more highly organized creatures such as humans have five to fifty. The number of introns could be related to the number of times a gene has been transported across a species boundary during evolution. This happens by a surprising mechanism the RNA transcript of the intron is spliced directly into the DNA gene. The phenomenon of homing by introns is not yet explained by any theory.