25/3/2018

Human Mating Seasons: The surprising link between your birthday and place of birth— in one heat map

 

It’s no news that humans are creatures of habit. We have specified times for everything, from gorging ourselves on turkey stuffing and gravy to going on extreme pre-summer diets to get our bodies ready for the sun.

But what about mating? While we usually don’t think of it in these terms, humans—like animals—also seem to have mating seasons. Well, sort of.

Take a look at the heat map below, created by the team at Visme. Based on the most recent UN data on live births, it clearly shows that there is a rather surprising and unexpected correlation between three different variables: the top birth months, seasons of the year and the latitude of the country (distance from the equator).

After looking at this data visualization carefully, did you notice that the top birth months for most northern hemisphere countries are July, August and September?

And did you notice that the lower you go down the list, the farther right the top birth months appear, eventually spilling over into the first months of the year?

While the majority of the middle-latitude (or tropical) countries register September and October as their top birth months, Southern hemisphere countries such as Uruguay register their top birth months at the start of the year.

How we created the infographic

Using the latest UN data on live births per month, we obtained figures for all the countries listed, for the years between 2000 and 2015.

To account for the fact that the number of days in each month varies, we calculated the average number of live births per day in each month and then ranked all 12 relative to each other, from highest to lowest.

To do this, we first downloaded all the available data from the UN Data site, which was conveniently available as an XML or CSV file.

We then opened the file in Excel and selected the Pivot table option to analyze and summarize the data.

We started by filtering the data to display only the sum of live births between 2000 and 2015. We then proceeded to calculate the average number of live births per day for each month. Using the Excel RANK function, we were able to rank each month relative to each other for each country.

To facilitate comparisons between countries with vastly disparate live birth numbers, we connected our Excel sheet to Tableau, which allowed us to create a color-coded scale to match each ranking with a shade of blue—the darker the shade of blue, the higher the ranking of a particular month for a specific country.

Next, using a 40-week gestation period and this conception calculator, we also determined the peak months of conception for countries around the world, based on the UN data for live births per month.

For example, we found that the top month of conception for many countries, including the US, Japan, Canada and Mexico, is December. In this infographic created with Visme, you can also see that many European countries such as Denmark, Finland and Norway register October as their peak conception month.

Non-designers can use Visme’s drag-and-drop software to create all sorts of visuals, from infographics with bits of data to purely textual information.

To start, create a free account here with your name and email. Then select an infographic template or start from scratch, and upload your Excel file or Google sheet to create simple charts, graphs and interactive maps.

So, do humans really have mating seasons?

While it may be tempting to buy into the age-old assumption that winter is the ideal time for being intimate with your partner because of colder temperatures, scientific research seems to indicate that the factors behind this trend are a little more convoluted than we think.

For example, according to one study, the perfect conditions for conception are when the temperature is between 50 and 70 degrees and the sun is out for 12 hours, perhaps because these conditions stimulate the production of sperm or ovulation.

Meanwhile, another study on human birth seasonality concluded that peak birth months occur later in the year the farther south you travel, which is completely consistent with the trend revealed by our data visualization.

Image: Micaela Martinez-Bakker, Kevin M. Bakker, Aaron A. King, Pejman Rohani.

 

A third publication on the topic by Boer Deng concluded that northern hemisphere countries exhibited peak birth months in the fall. On the other hand, southern hemisphere countries registered peak birth months in the winter, which also corroborates our findings.

Using proxy measures for sexual activity, such as Google searches, it was also found that queries related to sexual relations increased during the winter and early summer months.

Clearly, there is a complex combination of both environmental and biological factors at play here, but what is certain is that humans don’t have a true mating season, like animals do. While certain animals only mate during certain seasons, women ovulate every 28 days and have sexual relations during the entire year. It is interesting to note, nonetheless, that our heat map and several studies on the subject indicate that we have what appears to be a quasi-mating season, even if not a true one scientifically speaking.

About the author

Nayomi Chibana is a journalist and writer for Visme’s Visual Learning Center. Besides researching trends in visual communication and next-generation storytelling, she’s passionate about data-driven content. Email her at .(JavaScript must be enabled to view this email address).

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