According to an article in Scientific American:

Homo sapiens is the only species that keeps detailed records. That is why biologist Virpi Lummaa of the University of Sheffield in England started in 1998 to comb through Finnish church records from two centuries ago for clues about the influence of evolution on reproduction.

The data and analysis may have historical and even sociological value. Perhaps there is even some anthropological points to be noted. But how is this evolutionary biology? The answer is a cliché, but still true: when all you’ve got is a theoretical hammer, every study is a nail. Once again, we have biologists desperately seeking relevance and self-worth.