As you may expect, I was skeptical about these big assertions about the importance of "memes" because the aliens would probably be thrilled by very different things than "memes" or "toothbrushing waves" and they could even use the toothbrushes themselves in ways that we couldn't have predicted.
So let me defend my viewpoint.
Genes spread by creating proteins and animals and by forcing the animals to reproduce so that they reproduce the genes (parts of the DNA code), too. Analogously, memes are able to rewire the brains of the people (and animals) and force them to impress (and infect) other people.
To some extent, this analogy works very well. And I remember that as a teenager, I was impressed by the observation that many seemingly different portions of the real world (e.g. evolution of species and development of new graphics cards or anything else, for that matter) share the same qualitative aspects of dynamics such as the competition.
There was a sociologist who had written a paper for us all to read - something he had written ahead of time. I started to read the damn thing, and my eyes were coming out: I couldn't make head nor tail of it! I figured it was because I hadn't read any of the books on that list. I had this uneasy feeling of "I'm not adequate," until finally I said to myself, "I'm gonna stop, and read one sentence slowly, so I can figure out what the hell it means."
So I stopped - at random - and read the next sentence very carefully. I can't remember it precisely, but it was very close to this: "The individual member of the social community often receives his information via visual, symbolic channels." I went back and forth over it, and translated. You know what it means? "People read."
Then I went over the next sentence, and I realized that I could translate that one also. Then it became a kind of empty business: sometimes people read; sometimes people listen to the radio," and so on, but written in such a fancy way that I couldn't understand it at first, and when I finally deciphered it, there was nothing to it.