假日狂欢使出生率激增

This is Scientific American - 60-Second Science. I'm Karen Hopkin. In the United States, there's a holiday that goes hand in hand with romance. . .

so much so that nine months later, there's a spike in the number of babies born. Valentine's day? Wrong!

It seems that people in the U. S. and in other predominantly Christian countries have been having some very merry Christmases indeed. That's according to a study in the journal Scientific Reports.

Scientists have long wondered why, in Western countries, birth rates spike in September and early October. The prevailing hypothesis for this phenomenon postulates that there is a biological adaptation to the solar cycles.

Luis Rocha of Indiana University co-led the study. He notes that nine months before this baby boomlet is the winter solstice.

And when the days grow shorter and the night grows long, well, humans seem to turn to procreation for recreation. However this hypothesis was built on observations pretty much restricted to northern hemisphere countries and also culturally Christian countries.

And some data suggested there might be something cultural going on. So for instance in Israel, it was previously observed that communities associated with different religions have birth peaks at different times of the year.

To try to separate the cultural from the biological, Rocha teamed up with Joana Goncalves-Sá of the Gulbenkian Institute of Science in Portugal. Together, they combed through data on a planetary level. . . comparing countries in the Northern and Southern hemispheres. . .

and countries with predominantly different cultures, in this case Christian and Muslim. But they didn't look at when babies are born.

They looked to see when, during the year, people around the world Google the word sex. Joana Sá: What we found, first, was that Google. . . searches for sex on google. . . are a very good proxy for sexual appetite and sexual, offline sexual interest.