DNA determinations on a population

Since, apparently, one can take a small bit of DNA from hair or skin and determine something about the source, I got to musing - could one set up a hepa filter or some such in a mall or some such and analyze the DNA of the collected samples and come up with something about the demographics of the community.

Trivial example, could one filter the air at our local WalMart and using DNA determine that the community is, say, of 79 percent Latino and Amerindian descent?

Sure. Assuming your hepa filter actually picks up enough hair. Your bigger problem is finding a place where a good, random sample of people from your community frequents. Then you have to make sure you’re getting a random sample of their hair (or whatever you’re using). Different people are going to shed at different rates, so some people will be over/under-represented.

In short… if you asking about technical aspects of using DNA to trace ancestry, that works reasonably well in the US where the population is pretty well understood. And as long as you don’t have too many people of mixed ancestry. “Latinos” are going to be hard to quantify, though, so that is more of a linguistic group than a biological ethnic group. Most “Latinos” in the US are mostly Native American or mixed European/Native American, and many are mixtures of other ethnic groups, or mostly European.

If you’re asking about how to get a good, representative sample, then that’s a different question, but on that can presumably be solved with some creative sampling techniques.

The first problem is that it’s pretty hard to determine ancestry using DNA. It’s possible, of course, but you have to look at many different genes to even make a decent guess.

The second problem that occurs to me is that you might not get all that much usable material released into the air. And furthermore, some demographic groups might tend to shed into the air at different rates (which could be caused by something as simple as favoring different hairstyles), which would mean that those who shed more would be overrepresented in your sample.

To summarize, it’s possible, but not a particularly good way to get any kind of usable information.

What would be really interesting would be to set up a study where you use the OP premise but add to it by having a person sitting next to the filter and recording his observations of the race of the people as they looked to him.

Of course this wouldn’t be terribly accurate as so many people are mixed, (for example I know of a Filipino/Swedish gentleman who looks like a Puerto Rican)

But it’d be interesting to compare the results of the filter, with the results of the visual observer

I think this would be a very poor approach because …

Or skin. Or individuals. Your data would be dominated by the guy who blew his nose next to the filter.

Wouldn’t sampling poop out of the sewer pipe be a pretty good representation of demographics? Obviously, the statistics may be skewed if one particular race has a greater degree of shitting-in-public-bathroom-phobia.