Yes, shaveblogging. A slight detour from the usual ancient history, but yet it retains some relevance. Although to be honest this whole "shaving" business is probably a bit new to most archaeologists. Be that as it may: I recently purchased an old safety razor. E.g.:
Mainly because I'd heard these suckers produce a fine shave compared to the modern multi-bladed jobs, supposedly because the blade is much sharper. I can safely report that this is largely true with some caveats:
-- You have to be much more careful; wicked cuts are common for the careless.
-- You have to pay more attention to angle, speed, and preparation to get the desired effect.
As Corey Greenberg says on Shaveblog (yes, there is such a thing), it will do better than a modern multi-blade, but only with some practice.
It's an interesting evolutionary issue, this nearly complete migration of technology from naked straight razors to safety razors to multiblades and probably many of the principles behind the transition can be usefully applied in some archaeological settings. Some reasons for the transition may be strictly technological, others functional, and still others reaching out into more general cultural trends and it illustrates the difficulty in isolating single features as causative drivers of change.
The key difference between modern and safety razors seems to be in the sharpness of the blade. Single double-edged blades are supposedly much sharper than their multiblade counterparts, thus cutting hair more efficiently, but also doing the same for skin much more effectively. Many have said you don't have to take as many swipes with a single blade because it cuts it the first time. The mutliblade cartridge attempts to do the same thing via somewhat duller blades, but utilizing multiple passes -- two blades = two passes with each stroke. The old animation of the first blade yanking the hair out a bit and the second blade cutting it again seems intuitive, but the resulting additional closeness may be a result of the multi-pass idea rather than the stretch-and-cut one. Still, because they are less sharp, they require more passes, but are less likely to nick skin, and don't require as much concentration. Just swipe, swipe, swipe away while you're still half asleep.
So what we have set up are traditional cost-benefit problems both from a time/effort and monetary standpoint. Probably, a 2-3 blade cartridge is more expensive to produce and package than a single blade; even today double-edged blades are much cheaper than the average cartridge. The benefits from a user perspective involve tradeoffs between cost, closeness, time, effort, and injury. Obviously, the selective environment has favored multiblades, with a minority of shavegeeks preferring the old standbys (still manufactured). Some obviously prefer the actual shave itself, but some are no doubt driven by a more stylistic preference to be somewhat anachronistic.
This has some precedent in archaeological theorizing which often takes the form of weighing the costs to produce objects with the costs/benefits of their intended functions along with certain other cultural/stylistic factors to explain why a particular form developed the way it did. But the technology can also be affected by other cultural and geomorphologic factors such as settlement patterns and the distribution of resources, respectively. Parry and Kelly (1987), for example, argued that the rather common pattern of low-tech 'expedient' stone tool technology -- mostly simple flaked implements -- among sedentary populations is a function of the ability to horde larger amounts of raw material in one place without having to lug it around (see also Teltser 1991). Microlithic technologies are often argued to have benefits for highly mobile populations because they produce a large amount of cutting edge with respect to raw material volume. And there are certain classes of tools with little or no functional utility -- elaborate fish-tailed knives of Predynastic Egypt, or the bloodletting blades used by the Maya (incredibly sharp for nicking one's willy for a bit of sacred blood, but not something you'd butcher a hog with).
So are multi-blade cartridges a predictable outcome of natural selection, or just a marketing gimmick designed by razor manufacturers to push $3 blades on us? Given the nearly complete replacement of single blade safety razors by their multi-blade counterparts, I would argue that there's more than marketing going on, but this is a fairly short time span to judge long-term trends by. Relatively carefree morning shaving balanced against higher unit costs and a somewhat rougher face seem to have tipped the scales decidedly towards multiblades. But as Greenberg has shown (by increasing the sales of these older devices through blogging and a single television segment), there may be a resurgence in old-timey shave technology although how large this turns out to be is unknown. Who knows, after a brief flirtation with fancy multi-bladed razors, we'll end up drifting back to single blades and a few more minutes in front of the mirror. In that case, future archaeologists would be left to ponder the brief Multiblade Phase of the late 20th and early 21st centuries and wonder what sort of "ritual significance" these brightly colored devices had for our society.
Refs: Parry, W.J. and R.L. Kelly. 1987 Expedient Core Technology and Sedentism. in The Organization of Core Technology, edited by J.K. Johnson and C.A. Morrow, pp. 285-304. Westview Press, Boulder CO.
Teltser, P.A. 1991 Generalized Core Technology and Tool Use: A Mississippian Example. Journal of Field Archaeology, Vol. 18, No. 3 (Autumn, 1991) , pp. 363-375
UPDATE: Speaking of shaving, I've always wondered about how widespread it was in antiquity. People depicted in Mesopotamia generally had beards, but Egyptians were usually portrayed with only false beards or entirely bereft of facial hair. THe page linked there indicates shaving was widely practiced in Dynastic Egypt. I don't recall any mummies (royal or otherwise) sporting full beards. I think some of the caucasoid mummies found in China had facial hair, but I can't locate any photos showing it.
Another UPDATE: A reader emailed in to suggest that Gillette's motivation in changing their design from the standard double-edged single blade was to restrict blade use in its razors to those manufactured by Gillette, rather than a standard like the DE blade. Once they did that, they could keep things going with periodic "improvements" like more blades.
This sounds plausible, but as far as explaining why a particular form became fixed in the population, it's kind of irrelevant. Whatever the ultimate motivation was, a new design has to confer some benefit or it won't be adopted (read 'benefit' as a combination of the various factors above, not as 'better'). See New Coke for one of probably many examples where the simple introduction of a new product failed.
One might argue that Gillette had such a monopoly that they could basically do whatever they wanted and it would become fixed regardless. Not sure how this would pan out or not; after all, look what happened to Microsoft's Bob.
This is what those who use natural selection/Darwinian evolution for archaeological purposes argue: the source of the variation -- invention, inspiration, whatever -- is irrelevant as to whether a particular variant becomes fixed. This is mostly backwards to what common sense tells us, that change comes from the human mind seeing a problem and solving it; necessity as the mother of invention.