Births don’t happen uniformly throughout the year. Since several years, researchers are trying to understand if human reproduction cycle depends on biological factors, such as different the duration of the day, or cultural factors (holidays, for examples), or both factors together.

In 2017 Wood and collaborators from Indiana University published a paper in which they tried to answer to this question.

First, the researchers grouped the countries according to their predominant religion: Christian or Muslim one. Then, they analyzed the frequency by which people searched for the word “sex” using Google during the main religious holidays: Christmas in Christian countries and ʿīd al-fiṭr, at the end of Ramadam in Muslim countries. They found that in these periods the searches regarding sex topic have a peak, regardless of the hemisphere. This online interest, when shifted by nine months, corresponds to a peak in human births. Thus, the researchers gave a further proof for the cultural factor.

Moreover, they analyzed tweets on Twitter and evaluated the mood of the users. During the holidays the average mood was more calm and happy compared to other periods of the year. Their results show that the sexual and reproductive behavior is mostly driven by cultural and religious celebrations.

My daughter was born in September, so, probably, it is true that we love each other more during the holidays.

Reference:

Wood et al., “Human Sexual Cycles are Driven by Culture and Match Collective Moods”, (2017), https://doi.org/10.1038/s41598-017-18262-5