[Lester Moore]

By calculating the ratio of old-to-young individuals in the samples, the scientists found that the number of surviving older people increased throughout human evolution.

And the sample is how many?

[jennyp]

And the sample is how many?

That information is restricted to the small, privileged subset of people who read the article. :-)

The findings, published today by Dr Caspari and Dr Sang-Hee Lee in the Proceedings of the National Academy of Sciences, were based on a comparison of more than 750 tooth fossils from successive time periods.