How do we know that information was not "front-loaded" from the beginning in DNA? I have read that fishes and reptiles have much more DNA than humans. It would have mean that they could hypoteticaly bear information for them as well as for us.
Interesting question. First of all, if there were genes in fish (say) containing instructions for humans (say) but
not expressed, then they would have no bearing on the fitness of fish, and so natural selection wouldn't prevent the degradation of these genes millions of years before we could use them.
How do we know that some gene present in human is not present in fish?
There are such genes, as there should be.
Scientists are often surprised how many genes we have common with unrelated species.
There are no unrelated species, and scientists are not surprised.
Maybe function gene in human is split into four parts in fish and it seem to "dormant" or "junk" in fish ... So - how do we know that other genes are not there too but somehow splitted into parts?
Given that all DNA is made of combinations of just four bases, one can trivially get any human gene by shuffling fish DNA, in small enough chunks.
If I make an anagram out of selected portions of, say, the text of
Moby Dick, does that mean that the information in the anagram was always present in
MOby Dick?