Is it not reasonable to focus on, and request an explanation for, an integral part of a theory which, as far as he is aware, has no explanation? Recombination is the standard driver of evolution, true, but that does not mean that all other methods can be easily written off as irrelevant. Whether or not he has a thorough understanding of evolution, the question posed needs an answer.
That being said, one means that genetic material may be added to an organism is "failed" mitosis or meiosis(nondisjunction, aneuploidy, etc), where extra copies of the same chromosome are brought into the same cell. While often times these events are detrimental to organisms(especially the more complex ones, like humans), that does not make it harmful to all creatures 100% of the time. Therefore, its only a matter of time before this information is whittled down to more useful configurations.
I'm sure there are other means, and I'll be looking through
Nature, and other such publications for them soon.
edit: Another means by which genetic material may be added is through viral gene injection. Often viruses have destructive self-duplicating genes which get injected into the host cell, however, due to the large volume of viruses which may be produced, there is an increased chance of variations within their resulting genes, some of which may prevent viruses from injecting these destructive self-duplicating commands, enabling the rest of the genetic information to be passed on the other cells/organisms.
edit2:
http://www.talkorigins.org/indexcc/CB/CB102.html
Jam it back in, in the dark.
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