Pants Were Optional, 100,000 Years Ago

RobertB-DC writes "German scientists have used differences in the DNA of lice to determine when humans started wearing clothes. It seems lice are highly specialized -- head lice lay their eggs only on hair, while body lice hide theirs in the folds of clothing. Using the differences in the two species' DNA and a "standard" mutation rate, the scientists determined when clothing-specific lice (and by extention, clothes) came into existence. No comment, though, from Calvin Klein."

Comments

Sadly...

[danratherfan]

washing clothes wasn't invented until 5,000 years ago.

Huh?

[BladeMelbourne]

Pants are still optional, depending upon where you like to [let it] hang out.

Re:Huh?

[macdaddy357]

Yeah! It's no shirt and no shoes that will get you no service. They don't mention pants.

We naturists...

[n1ywb]

We naturists have known for some time that pantsless is the way to go. No news to us.

Re:For follow-up research

[spectral]

I'd be more interested in finding out whe dressing up became the norm. I don't see why what I look like matters as much as my ability to do the job and do it well.

Hrm...

[asdfx]

They're not optional now? That probably explains a few things...

This...

[FreeMath]

comes as no supprise to CmdrTaco, as he has long known that:

Pants are optional, but recommended for you.

Re:For follow-up research

[Mad Marlin]

I don't see why what I look like matters as much as my ability to do the job and do it well.

You must be a programmer.

How accurate is this really?

[gooru]

Using the differences in the two species' DNA and a "standard" mutation rate, the scientists determined when clothing-specific lice (and by extention, clothes) came into existence.

The article states that the "scientists" calculated one metronome per 30,000 years and thus concluded that body lice branched off from head lice about 72,000 years ago. What?!?!? How likely is it that mutations really occur on average without much of a deviation from the mean that regularly? For all we know, mutations occur in leaps and bounds. It might be very similar to those annoying studies of amortized cost in my algorithms classes. Sure, great, probability theory is great and all, but what about reality?

Re: How accurate is this really?

[Black Parrot]

> The article states that the "scientists" calculated one metronome per 30,000 years and thus concluded that body lice branched off from head lice about 72,000 years ago. What?!?!? How likely is it that mutations really occur on average without much of a deviation from the mean that regularly?

You do have to be careful about that sort of thing. For example, attempts to apply the same logic to language (glottochronology) are not generally accepted by linguists because so much of language change is driven by social factors rather than blind mechanistic processes.

> For all we know, mutations occur in leaps and bounds. It might be very similar to those annoying studies of amortized cost in my algorithms classes. Sure, great, probability theory is great and all, but what about reality?

I'm certainly no expert on this, but there are several things that appear to be working in favor of using mutations as a biological dating system. For one the molecular mutations that form the basis of the method do appear to be the result of blind mechanistic processes - at least if you can avoid the error of measuring parts of the genome that are subject to pressures for or against preservation or change. For another you've got the Law of Large Numbers working in your favor, both in terms of the size of the DNA molecule and the number of generations. Unless we're missing something these factors should conspire to give us an expected value for the mutation rate and an opportunity to average it over a very large number of events (length of DNA * number of generations), allowing us to apply standard statistical methods to calculate an expected value for the number of mutations and a confidence range for it.

Also, we live plenty long enough to measure mutation rates between generations of organisms today, including humans as well as lice and other species. It should be pretty easy to calculate an expected value of number of mutations per unit length of DNA per generation, and see how much variance there is in that number today, and compare that to what our calculations suggest for the evolutionary timescale. (I'm not familiar with the literature on the actual numbers but I know at least some of it has been done, because a few years ago I read something about the typical number of mutations observed in human babies. I'm not citing the number because I don't trust my memory on it. But the fact that they could even name a number goes far toward establishing the kind of model you need for this kind of dating.)

A big problem for the method would be if mutation rates have changes significantly over time, e.g. due to radiation or environmental chemistry, and this kind of stuff is hard to check directly. However, science is "convergent" in the sense that we expect our various theoretical approaches to give the same answer if they are in fact correct, so the fact that this study produces a number that matches the previously established number for when our ancestors left Africa and moved into regions where clothes would be necessary, all adds up to a satisfyingly consistent model of what happened to cause all the relevant observations.

There is of course the epistemological problem of the inability to prove anything in the empirical sciences, but since that problem is unsurmountable we more or less ignore it and take our supportable results as "true" - but not as "Truth" - so long as the explanation seems to work and converges with all our other models for what's going on in the universe. If we discover later that we did something wrong we simply have to revise our results when that time comes, but that's an unavoidable risk we have to take; the only other alternative is to throw up our hands in despair and not try to understand the world at all.

If you want a more expert analysis of any of this you might want to post it as a question on talk.origins, which is inhabited by all manner of biologists, mathematicians, etc., who can daze you with more than you want to know about virtually any topic.

Re:Atricle has flawed logic IMO

[Robb]

I think they overstate their case but it is not entirely flawed.

Evolution may be slow but it can express itself in a population very quickly. An adaptation that provides no specific advantage may spread through an isolated group (keep in mind this is happening in a huge number of groups). Then at some point in time it does become an advantage so the population of this group explodes as it expands into the newly created niche.

The fossil record provides strong evidence that changes in populations occur very quickly (i.e. tens of thousands of years) even if it provides no direct evidence on the speed of evolution.

Re:Atricle has flawed logic IMO

[Lars Arvestad]

This is what the actual paper in Current Biology by Kittler et al says:

A critical assumption is that the origin of body lice reflects the origin of clothing; it is possible that clothing existed for some time before lice exploited this new ecological niche, in which case the origin of clothing could be much more ancient than the origin of body lice. While we cannot exclude this possibility, the colonization of a new ecological niche usually occurs rapidly after it becomes available. Since modern humans and archaic humans such as Neandertals diverged about 250,000-500,000 years ago, in order to associate clothing with archaic humans, clothing would have had to exist for hundreds of thousands of years before the origin of body lice, which seems improbable. Moreover, archaeological evidence does not contradict an association of clothing specifically with modern humans, as the only tools that can be definitely associated with clothing, such as needles, are only about 40,000 years old.

So they certainly address the issue. These guys are not naive---The last author, Mark Stoneking, is a very experienced and respected investigator.

Their dating is actually 72000 +- 42000 years btw.

pants have their advantages

[Ender Ryan]

1. not accidentally cooking part of yourself
2. not getting part of yourself caught in a belt sander
3. preventing wind/sunburn
4. hiding it when it's cold

Re:pants have their advantages

[3waygeek]

You forgot the biggest benefit of pants -- pockets.

Fashion in Ancient History

[Alliante]

If I recall correctly (I'm no historian), skirts/kilts were more popular due to the ease of fabrication back then.

I would think that it would make sense that these types of lice could infest the nether-regions as if they were pantless.

Re:For follow-up research

[radtea]

"Dressing up" became the norm (that is, for normal people, as opposed to the extremely rich or aristocratic people) about two hundred years ago, when industrial technology made cheap clothing available to the normal people.

--Tom

A scenario

[exp(pi*sqrt(163))]

Lice could have made the jump from fur to clothing many times. If the last time it happened the lice were so successful they displaced the previous species we'd only see one recently jumped species today. You really need a lot of caution with this data even if you do assume that evolution rapidly fills new niches.