I congratulate the authors on this exciting study. Interestingly, one of the most famous Russian fairy tales by Alexander Pushkin builds on what could be interpreted as a pre-wedding promise of sex ratio manipulation in favor of males.

Without being noticed, the tsar occasionally found himself listening to three beautiful girls chatting. They were discussing what they would do if they became tsar’s wife. One said that she would weave for the whole world. The second one said that she was going to cook and prepare a great party for the whole world. But the third sister said that if she became the tsar’s wife, she would give birth to a hero. Upon hearing this, the tsar immediately disclosed himself, offered her to become his wife and to give birth to the hero “by the end of September” – which she did. The story in full is here http://www.englishforkids...

The fairy tale builds heavily on Russian folklore so this pledge to give birth to a son does reveal some cultural encoding. It is an exciting research topic.

My question to the authors is whether they would be willing to archive their original data (the pedigrees) to enable other researchers to independently verify their numerical conclusions and possibly contribute to their analysis.