I like to compare this development to the revolution that happened among the bacteria roughly a billion years ago. Relatively simple prokaryotes got invaded by some of their neighbors, and the resulting endosymbiotic teams were more fit than their uninfected cousins, and prospered. These eukaryotes, living alongside their prokaryotic cousins, but enormously more complex, versatile and competent thanks to their hitchhikers, opened up the design space of multi-cellular organisms. Similarly, the emergence of culture-infected hominids has opened up yet another region of hitherto unoccupied and untraversable design space. We live alongside our animal cousins, but we are enormously more complex, versatile and competent. Our brains are bigger, to be sure, but it is mainly due to their infestation by memes that they gain their powers. Joining forces with our own memes, we create new candidates for the locus of benefit, new answers to Cui bono?
3. Darwin's Path to Memetic Engineering
Here I think we can get help from Darwin's opening exposition of the theory of natural selection. In the first chapter of Origin of Species, Darwin introduces his great idea of natural selection by an ingenious expository device, an instance of the very gradualism that he was about to discuss. He begins not with natural selection--his destination--but what he calls methodical selection: the deliberate, foresighted, intended "improvement of the breed" by animal and plant breeders. He begins, in short, with familiar and uncontroversial ground that he can expect his readers to share with him.
We cannot suppose that all the breeds were suddenly produced
as perfect and as useful as we now see them; indeed, in several cases, we know
that this has not been their history. The key is man's power of accumulative selection:
nature gives successive variations; man adds them up in certain directions useful
to him. [p30, Harvard facsimile edn]
At the present
time, eminent breeders try by methodical selection, with a distinct object in
view, to make a new strain or sub-breed, superior to anything existing in the
country. But, for our purpose, a kind of Selection, which may be called Unconscious,
and which results from every one trying to possess and breed from the best individual
animals, is more important. Thus, a man who intends keeping pointers naturally
tries to get as good dogs as he can, and afterwards breeds from his own best dogs,
but he has no wish or expectation of permanently altering the breed. [p34].
Darwin pointed out that the line between unconscious and methodical selection was itself a fuzzy, gradual boundary:
The man who first selected a pigeon with a slightly larger tail, never dreamed
what the descendants of that pigeon would become through long-continued, partly
unconscious and partly methodical selection. [p 39]
This nesting of different processes of natural selection now has a new member:
genetic engineering. How does it differ from the methodical selection of Darwin's
day? It is just less dependent on the pre-existing variation in the gene pool,
and proceeds more directly to new candidate genomes, with less overt and time-consuming
trial and error. Darwin had noted that in his day,
We can use Darwin's three levels of genetic selection, plus our own fourth level, genetic engineering, as a model for four parallel levels of memetic selection in human culture. In a speculative spirit, I am going to sketch how it might go, using an example that has particularly challenged some Darwinians, and hence been held up as a worthy stumbling block: a cultural treasure untouchable by evolutionists: music. Music is unique to our species, but found in every human culture. It is manifestly complex, intricately designed, an expensive consumer of time, energy and materials. How did music start? What was or is the answer to its Cui bono question? Steven Pinker (1997) is one Darwinian who has recently declared himself baffled about the possible evolutionary origins and survival of music, but that is because he has been looking at music in the old-fashioned way, looking for music to have some contribution to make to the genetic fitness of those who make and participate in the proliferation of music.  There may well be some such effect that is important, but I want to make the case that there might also be a purely memetic explanation of the origin of music. Here, then, is my Just-so Story, working gradually up Darwin's hierarchy of kinds of selection.
Natural selection of musical memes.
One day one of our distant hominid ancestors sitting on a fallen log happened to start banging on with a stick--boom boom boom. For no good reason at all. This was just idle diddling, a byproduct, perhaps, of a slightly out-of-balance endocrine system. This was, you might say, mere nervous fidgeting, but the repetitive sounds striking his ears just happened to feel to him like a slight improvement on silence. A feedback loop was closed, and the repetition--boom boom boom--was "rewarding". If we leave this individual all by himself, drumming away on his log, then we would say that he had simply developed a habit, possibly therapeutic in that it "relieved anxiety," but just as possibly a bad habit--a habit that did him and his genes no good at all, but just exploited a wrinkle that happened to exist in his nervous system, creating a feedback loop that tended to lead to individual replications of drumming by him under various circumstances. No musical appreciation, no insight, no goal or ideal or project need be imputed to our solitary drummer.
Now introduce some other ancestors who happen to see and hear this drummer. They might pay no attention, or be irritated enough to make him stop or drive him away, or they might, again for no reason, find their imitator-circuits tickled into action; they might feel an urge to drum along with musical Adam. What are these imitator circuits I've postulated? Just whatever it takes to make it somewhat more likely than not that some activities by conspecifics are imitated, a mere reflex if you like--of which we may see a fossil trace when spectators at a football match cannot help making shadow kicking motions more or less in unison with the players on the field. One can postulate reasons why having some such imitative talents built-in would be a valuable adaptation--one that enhances one's genetic fitness--but while this is both plausible and widely accepted, it is strictly speaking unnecessary for my Just-so Story. The imitative urge might just as well be a functionless byproduct of some other adaptive feature of the human nervous system. Suppose, then, that for no good reason at all, the drumming habit is infectious. When one hominid starts drumming, soon others start drumming along in imitation. This could happen. A perfectly pointless practice, of no utility or fitness-enhancing benefit at all, could become established in a community. It might be positively detrimental: the drumming scares away the food, or uses up lots of precious energy. It would then be just like a disease, spreading simply because it could spread, and lasting as long as it could find hosts to infect. If it was detrimental in this way, variant habits that were less detrimental--less virulent--would tend to evolve to replace it, other things being equal, for they would tend to find more available healthy hosts to migrate to. And of course such a habit might even provide a positive benefit to its hosts (enhancing their reproductive chances--a familiar dream of musicians everywhere, and it might be true, or have been true in the past). But providing a genetic benefit of this sort is only one of the paths such a habit might pursue in its mindless quest for immortality. Habits--good, bad and indifferent--could persist and replicate, unappreciated and unrecognized, for an indefinite period of time, provided only that the replicative and dispersal machinery is provided for them. The drumming virus is born.