Do humans have a mating season?

(للقراءة بالعربية)

Humans clearly have some concept of a mating season as a set of months in which people prefer to start a pregnancy, and that season depends on many factors such as the temperature and the change in temperature. Seasons themselves are representations of light and temperature, therefore when we investigate further about temperature, we find that countries are either preferring the months when the temperature starts increasing or when it starts decreasing. Those who live in cold areas prefer the months of the highest decrease in temperature for having sex, and those who live in hot areas prefer the months of the highest increase in temperature.

Introduction

The first time I had this question was in 2017, I worked then to collect multiple datasets including a very good dataset of births per country per month since the year 1967. I’ve also got data for average temperature per country and data for climate classifications according to the Koppen-Geiger classification. However, I didn’t publish anything about my simple statistical work in 2017 and I found that someone else in Medium has done similar work but not with the same details and the same research questions that I asked.
The question about a season should lead us to a specific month or a set of months, but the mating season is affected by other factors like the temperature and the light. Light and temperature have variance across the different countries or regions. Therefore, I tried to rely on the data that I found for the average temperature per month and per country. For light, I couldn’t find a useful source, I found datasets that are related to cities not to countries, and this should be the case for all the other pieces of data in this small study, but we are limited to the data that we find. However, looking at birth patterns in the births data per month per country and correlating them with temperature and geographical regions is still very interesting.
Climate classification is also a type of data that isn’t generalizable to a country as a whole, but to a smaller region. However, it was possible to exclude some countries that have a variety of climate classifications, and it was also possible to take either the higher classification that could be generalized over the whole country or to take the climate classification where the majority of the country’s population live.
An average of the births data has been taken for each country over the years. Then I selected the top 3 months in births for each country, then I subtracted 9 months from the top 3 months to get the top 3 months (mating season) for the country.

Temperature

After joining the data together, each country now has its average temperature and its average births per month, so there’re 24 fields of temperatures and births for 100 countries. The first thing I’ve done was to see if there’s any correlation between temperature and births, but nothing was interesting except the correlation between total births in summer months June, July, August, and the average temperature values of these months. The correlation value was slightly higher than the rest of the months 0.11,0.12,0.13 for June, July and August consequentially. That means that there’re more births when the temperature is higher, and that includes the upper hemisphere of the earth as the majority of the countries in the dataset were from these countries. However, having a small correlation value doesn’t mean having significance, it was just something I’ve noticed, and I wouldn’t have given it any importance if it wasn’t happening with summer months specifically.
The other thing I’ve examined is the relation between the month when pregnancy happens more than other months (will refer to it as PM in this article) and the temperature in that month in relation to the other months for each country. So, based on the temperature, each month will have a sequence (1-12) where (1) is the hottest month and (12) is the coldest month, no matter what really (1) and (12) are in the real sequence of months. I found that month (8) is the month is the PM, followed by months (9-12), and it happened that in the majority of the countries the month (8) and was mainly either November and October. From that, we can conclude that humans prefer temperate months that tend to be cold as their mating season.

What about the temperature itself? Is there a preferred temperature for the mating season for humans? I don’t know if we can ask the question in this way as it is a “preference” or innate behavior, but anyway, I made the temperature of the top 3 PM in groups to make it easier to understand them, and I’ll include some explanation about these groups as the average temperature for the whole country isn’t something that we’re familiar with:

1. 20s: this group includes countries that have at least two PMs with an average temperature in the 20s. Autumn in Iran, or spring in Egypt and Algeria belong to this group.
2. 10s: The temperature is 0-10c in at least 2 PMs. Examples of this type of weather in November in many European counties such as France, Belgium, Germany, Bulgaria, and Belarus.
3. 10-20: 2 PMs at least are within the range between 10-20 degree. Many months in temperate countries could be represented by this group.
4. -10-10: 2 PMs at least have their temperature between -10 and 10 Celsius. This group contains countries where the PMs had big differences and it was difficult to classify them within the previous groups easily.
5. Minus: 2 PMs at least have their temperature below zero.

The third question I had about temperature is, do humans prefer the PM to be when there’s a big change in the temperature? My data doesn’t help a lot, as big temperature changes happen in reality within days not months and the average monthly temperature isn’t the best piece of data to study that. However, I calculated the differences between every two months, for example, if October’s average temperature was 10 and in September was 14 then the difference of October would be (-4).
The goal of finding the highest differences and lowest differences (even negative ones) is to see if there’s any match between the months of high difference / low difference with the top 2 PMs. That will tell us if humans prefer that big difference in temperature. The result was that in 80 countries the top 2 PMs were either the month with the highest difference in temperature or the second-highest difference in temperature.
Countries where humans prefer the highest increase in temperature between months are the warmer countries, it includes Caribbean countries, and two south-east Asian countries, 4 countries from north Africa, Pakistan and Sri Lanka. Scandinavian countries could be seen also within the countries that prefer PM warm months as they prefer June and July, which breaks the rule of warm countries prefer months with change-to-warm in temperature. Countries that prefer the change to cold in temperature are mostly cold countries. From these countries that preferred the change to cold months, we can see Balkan countries, central and eastern European countries and all the north sea countries, in addition to 7 Mediterranean countries.

Month patterns

After finding the first pregnancy month (PM) by subtracting 9 months from birth month, the best way to look at the months was to split them into patterns. However, without the patterns it seems like November is the most preferred PM among many of the countries that have been included in this work. It is also possible to see that the period between October and January is the most preferred period for starting the pregnancy in humans, and we may call that period the humans mating season. But not to forget that September is also important in some countries and that there’re other patterns that include spring as we will see.

Creating the patterns has been done without any rule, except to find a way that insures fitting the countries’ top 3 PMs within some category. Sometimes I used seasons to describe the patterns and sometimes the patterns were just a selection of months.

Climate

Koppen-Geiger (KG) climate classification has been made initially to study vegetation growth. But it is still the most famous climate classification and it is also useful for many types of studies as it includes more than one aspect of climates’ features.
The first issue with using KG is that it’s not meant to be used for a whole country as there’re many countries in the world that contains more than one climate classification. Therefore, generalizing one climate classification doesn’t seem to be a correct thing. But if we look at the most inhabited areas in each country, we may find that it’s possible to take a specific climate classification for countries. For example, south Sahara African countries are mostly covered by BWk arid climate, but less than 1% of the population lives in these areas, while the majority of the population live in south areas with BSk or even A climates. It is also possible to take the higher classification of each climate class such as (A) or (B) and in that way it would be possible to generalize the climate class over a whole country, and this is what I’ve done here. It was also possible to include more than one class for each country and by that, it was possible to use KG classification for countries.
After distributing climate classes on the countries, I found no correlation at all with the top 2 PMs. Working with temperature alone was more useful than climate classes. But it was useful to use the climate classes as another type of pattern to look at.
For tropical countries with the class (A), it was possible to see that the PM was in the period between January and April for 15 out of 25 of these countries. The pattern of the summer was also noticeable in New Caledonia and Mauritius and it is a very rare pattern which moves us to the next fact that is: looking at the top 3 PMs in general for tropical countries, it is clear that there’s no significant pattern of months, probably because the weather is quite similar in all months for these countries.
For type (B) countries we can see that 9 out of 19 of these countries’ PMs are either March or April. Apart from that, there’s no other significant fact about B climate countries.
Two-thirds of countries where the majority live in a temperate climate (C) prefer November and December, followed by January and February. Similar results could be found for countries where the majority live in continental climate (D) but with a more preference to November.

Geographical regions

Unlike the climate, there’s no unified classification for geographical regions. Instead, there’re many geographical classifications for different purposes. Therefore, I created a geographical classification that contains regions already known in many other fields. Below I’ll mention the notes in front of the region if there are some, otherwise, I’ll only mention the region name:

1. Balkan: completely within Nov-Dec pattern except Albania. PM is November.
2. Baltic: contains 5 countries, top 2 PMs are June and July for Sweden, Norway, and Finland, while Latvia and Estonia do prefer November as their PM, but they still choose June as the second PM. All the 5 countries prefer September as the third PM.
3. Caribbean: PM for 14/16 of these territories’ top 3 PMs are either January or February. The second PM for half of these countries is March or April, and for 11/16 of them, the 3rd PM is also March or April. Simply, the matrix for these countries are full with numbers 1-4.
4. Caucasus.
5. Central Asia
6. Central Europe: the clearest pattern is preferring November.
7. Eastern Europe: PM is November.
8. Far East
9. India and surroundings
10.  Mediterranean
11. Near East: 3 countries only and they all prefer the spring
12. Northern Africa: March is the PM
13. Northern America
14. Northern Sea: all the countries except Iceland are within (C) climate categories. December and November are the most common PMs.
15. Oceania
16. Southern Africa
17. Southeast Asia
18. Southern South America
19. West Africa

What makes the image blurry?

In contemporary times, there’re many factors that make the image so blurry about the mating season. We don’t face nature as we used to do in the past, instead, we protect ourselves with good houses, air conditioning, and lighting systems. Therefore, we’re kind of living in an artificial environment. If there were some psychological traits or any effects by the weather, they would be reduced by the effect of the artificial life. Sociological effects would also be reduced by the effects of immigration and social mixing with different peoples.
Immigration can also add new communities with higher birth rates to some countries, even with a rate that is the highest in the country, similar to some communities in France and the UK. For that, it is not possible to assume the effect of any genetic or psychological factor when looking at the births per country, but it is only possible to look into the geographical features. For example, it is not easy to study the “British” people’s preference, but only to look at Britain as a region.
The other factor that affects the normal birth rate around the world is the birth control methods. Condoms and pregnancy pills make people more capable of choosing when to have a child and so they affect the natural birth and pregnancy rate and time. Many nations now have negative population growth these days, and that was not ever a usual thing under normal circumstances.
In addition to all that, the main reason for having a blurry image is the data itself, for all the reasons explained about the climate, the missing countries, and other vulnerabilities in this work.

Suggestion for supporting data

In addition to the need to have the data of all countries, there’re some suggestions that may help in finding the mating season of humans by other supporting pieces of data, such as the season of weddings in each country, sales of condoms data, surveys, or data of visits to porn websites per countries per months.

Why didn’t I publish this work?

1. I don’t know what’s the suitable field and domain for this work.
2. I have no time for documenting and research writing.
3. My appetite for scientific publishing is gradually being reduced as I see the scientific publishing goes sometimes to be a complex process of rituals and formalities.
4. I lost many chances to write about works I’ve done, just because I thought it’s not suitable to publish yet, and I never took the time to finish them. So why don’t I just publish a minimized version?
5. The problems that I’ve mentioned in this work don’t make it good enough to be academic work.