Size doesn't always matter

By Razib Khan | August 26, 2010 11:56 am

The autosomal genome of Ă–tzi the Austrian “Iceman” is apparently in the pipeline (from what I can tell they’re doing the analysis right now). What can we learn from one sample? Ann Stone, who was a graduate student on the original team which recovered his body, says:

A specialist in anthropological genetics, Stone is excited by the recent news but also cautious. “It is a sample of one. For us to really say something about that period, you need a sample of 25 to 50 individuals,” she explained during an interview with Deutsche Welle, Germany’s international broadcaster.

This is fine as it goes. Worries about sample size are pretty generic and if the practicalities permitted who wouldn’t want a bigger N? But whether you should worry about sample size is partly conditional on how much the findings deviate from what you’d expect. Imagine for example that ~25% of Ă–tzi’s genome was of Neandertal origin. Obviously it would be great to have 25 to 50 representative individuals from this region to know whether Ă–tzi was atypical…but the very finding itself would be of such large effect that an N = 1 would tell us quite a bit. Similarly, one genome of a Sub-Saharan African would be very informative if you had several hundred non-African genomes as a point of comparison (because Sub-Saharan Africans have so much genetic variation which is outside of the distribution found among non-Africans).

MORE ABOUT: Ă–tzi, Sample Size
  • David Boxenhorn

    If you think of every gene as a sample, then the sample size is huge.

  • John Emerson

    I think that she was just trying to chill out the inevitable excitement that will arise when it is found that Otzli was Jewish and related to Hitler.

  • Marnie

    Ha, ha, John.

    I was worried there for a moment that we were about to find out something intimate about Otzi’s anatomy that we didn’t really want to know.

    Otzi’s genome comes with an appearance and the things he was carrying. For instance, he was carrying a bronze age copper axe. Although it is a sample size of one, it is more interesting that a sample from bones alone.

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  • Ann D.

    @ John: I did wonder why Razib referred to him as an Austrian :-)

  • Marnie

    Anybody else catch the CBC radio “As It Happens” interview with Alessandro Vanzetti regarding Otzi?

    If you can’t pick up the interview, here’s the Alessandro Vanzetti annoucement:

    To be honest, I would love it if Otzi was carried into the mountains for burial by his friends.

  • bioIgnoramus

    Irish. I’ll vote for his proving to be Irish.


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About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at


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