“ Mutation only loses information…”
Well nooo …. theoretically; it could happen.
But there’s no evidence that it can gain significant information at a quantity or rate sufficient to support the theory of evolution.
The information in DNA is encoded in 4 bases abbreviated as CATG. In themselves these bases don’t mean anything in the same way that the letters a-z don’t mean anything in themselves, but just as the letters of the alphabet can be arranged into words and sentences to encode information so the 4 bases can be arranged in “words” of 3 bases called codons, and the codons into sequences, to encode information, the amino acid sequence in a protein. But there is no chemical or mechanical coupling between a codon and the amino acid it codes for, which is why the genetic code is not quite universal; a codon can code different amino acids in different organisms. So DNA is a symbolic code like a language or even a computer code .
If you take say, the Gettysburg Address, and start making random changes to it what is the chance you will produce a completely new meaningful document? For practical purposes, nil. You will soon have a page of gibberish. In the same way making random changes to a gene will almost certainly destroy any function of the gene long before it produces any new functional information. In fact it’s worse for a gene than for text because on average any codon is part of the code for 5 different proteins, so even if you improve one you will probably impair others.
But still some minor improvement is possible. In bacteria mutation + natural selection can start with an enzyme with low action on nylon and significantly increase its action. But this is a trivial change, as demonstrated in the book “Only a Theory”.
Or to take another example; we have a toaster with a blown element on one side so it now produces one sided toast. You could say that it has gained a function because it now produces something it didn’t before, but clearly it is just producing a faulty version of toast.
Similarly people with Sickle Cell Anemia have DNA that has mutated at one point. Because of this, many of their red blood cells are produced in the shape of a sickle , a faulty version of normal red blood cells. If you get one copy of this gene your health is impaired, if you get 2 copies it will be fatal without medical attention. However where the incidence of malaria is high people with a single copy of the gene get protection from malaria and there is nett benefit, but even so the frequency of the faulty gene never rises above 20% in the population because of the associated adverse affects.
The sickle cell example shows that you should not confuse benefit with information gain. Another example of this is where a defect in regulation of lactase production allows adults to digest lactose in milk. It’s a loss of genetic information that produces a nett benefit.