We are programmed to survive as individuals and as a species on this planet. Just like any other life form.
To ensure this, each couple should have two children who will become parents themselves.
Among animals, many species produce huge amounts of 'babies' and most get eaten. Frogs lay thousands of eggs, many turn into tadpoles and get eaten. On average, only two survive to become frog-parents again. Otherwise frogs would be extinct or cover the planet by now.
We are different as we are more clever and started to use more and more tools that would help us to survive ‘more’. Our babies also need so much more care and attention over such a long time, that 'mass' babies is just impossible.
Still, to ensure that at least two of our children make it to become parents, we traditionally have had more than two children. Very poor societies used to reach up to 8 or 9 births for every woman. World average seems to have been about six live births per woman.
But, now it is less!
Until the 1800s, almost four of six children died before becoming parents themselves. Only two children did became parents. At that time, we counted one Billion people on the planet.
In the West, ever since the industrial revolution and the huge wealth benefits it created, medical science has made great advances. Societies started to provide the resources to care for people, resulting in a huge decrease in the number of children dying before the age of five.
Germany, in 1840, half of the kids would not live to be five, let alone become parents themselves. Fast forward to the year 2000 and only five of a thousand live births in Germany did not reached the age of five. Somehow ‘instinctively’, women have reduced the number of children they have from five to now even below two children. Roughly, over time, they ensured two kids would become parents. Urban life also changed the outlook: Farmer kids helped harvesting, city kids needed extra resources. Many kids were 'assets', helping and later taking care of the old. Now they need extra rooms, school trips any much more. They have become a 'liability'. However, they all become parents later.
During the same period, German life expectancy went from 38 years in 1840 to almost 80 years in 2000. Similar figures all other industrializing nations.
Being pregnant and giving birth is a very exhausting experience. By ntoday, a woman only ‘needs’ to do this twice as she can be confident that her children will live to be parents in 20 years and thus ensure the survival of the species. I’m not saying that these are her motives, it’s the human programming. It is economical.
By now, trend is worldwide. The UN recently released a prognosis of world population. By 2100, we will be 11 Billion people and that will be it. The reasonable expectation that two kids will become parents goes for many nations today and will include more and more, eventually all. Advances in hygine, medication, schooling, everything, increasingly extends across the globe.
Already now, the number of children worldwide remains at 2 Billion, constant.
World population growth from the current 7 Billion to the 11 Billion will be mainly due to all of us just living a lot longer. Called filling the gap. Parents live longer, but have no more than two kids.
Check out gapminder.org for visualisation of statistical data collected from serious sources all around the world. This 16 minute video shows this convincingly and is very entertaining. You will love the guy!, Hans Rosling, Professor of health statistics at a Swedish university. It’s mind blowing and explaining this in detail. He sadly passed away in early 2017
Away from statistics, here is some personal stuff from my own life.
My dad had three brothers. The four of them teamed up with wives and managed to have five kids (should have been eight, right?). These five kids had only seven kids themselves. Europe is shrinking.
My wife’s mother, in a developing country, had ten children. One did die early, nine became adults. This suggests medical advances there too (or just good genes). Between the nine of her kids, 13 grand children (should have been 18) were born. The 13 grand children have so far had only one child, but we are still counting here.
These examples are below ‘replacement’ rates, i.e. two kids. Less than two children is the story today in Germany, Italy, Japan and many other rich countries. Hong Kong only has one birth per woman. The rest of Asia is moving very fast to the two child fertility, Africa is still on high birth rates and will provide most of the world wide population growth. However, its fertility is decreasing rapidly as well.
The unrepresentative bunch of people I happen to know are all on average way below two children.
If we manage to get sustainable energy, 11 Billion should not be too scary.