How did the global homo sapien population grow to 7 billion today if the fertility and mortality rate are meant to always balance each other out?

[mad_scientist]

What is the general consensus amongst the global scientific community?

[Strange]

Because more people were born than died.

 

the fertility and mortality rate are meant to always balance each other out

Why would that be the case? (It isn't.)

Edited June 6, 2017 by Strange

[DrP]

"How did the global population grow to 7 billion.."?

 

Sex - lots of sex.

 

 

I agree though - why should they balance out? Medicine has improved and life expectancies have increased. People live longer and there are no laws (in this country at least) that limit the amount of children you might have.

[swansont]

"How did the global homo sapien population grow to 7 billion today if the fertility and mortality rate are meant to always balance each other out?"

They weren't "meant" to balance each other out. The premise is false.

[mad_scientist]

"How did the global homo sapien population grow to 7 billion today if the fertility and mortality rate are meant to always balance each other out?"

 

They weren't "meant" to balance each other out. The premise is false.

As I have heard that human populations that have a high mortality rate typically have a high fertility rate (e.g. those in Subsaharan Africa) to make up for the babies/children who will not make it to old age. I have heard that there is a natural mechanism that keeps the human population from making too few babies or too many. Is this simply not true and not the case?

 

If not, then today why are fertility rates higher in regions of the world where death rates are correspondingly high?

 

With improved standard of living and healthcare it is anticipated that global fertility rates will go down. As people live longer, they will choose and want to have fewer children naturally. We see this all over the world today (e.g. Japan, Singapore) where people want to have fewer but higher quality children than people of their parent's generation when living conditions were harsher.

I agree though - why should they balance out? Medicine has improved and life expectancies have increased. People live longer and there are no laws (in this country at least) that limit the amount of children you might have.

I'm not sure. I think most people don't purposely decide how many children they want to have. It sort of happens subconsciously due to environmental cues such as war famine, disease and other signalling factors. I don't think human populations choose to increase or decrease their fertility rates on purpose but it is rather a response to environmental factors and stress. Edited June 6, 2017 by mad_scientist

[DrP]

"..natural mechanism.."

 

What natural mechanism? I think people make the choice. I think it is pretty logical to have more children when a higher percentage of them die.

 

"..is it anticipated that global fertility rates will go down.." - I would think so. Here in the UK it wasn't that long ago that having 6 to 12 kids was not seen as being that unusual. On my mother's side (she is one of 2) her father was one of 7 and his father was one of 12. On my Father's side (he is an only child) his mom was 1 of 6... her parents had more brothers and sisters than her. I don't think it was unusual.

 

I just looked up some data - apparently it was pretty normal to have on average 6 children in the Victorian age (UK)... this dropped to 3 in the early 20th century... latter part it was the classic 2.4... and now we are 1.9 (according to an article I just read).

[mad_scientist]

https://m.youtube.com/watch?v=hVimVzgtD6w

[Strange]

https://m.youtube.com/watch?v=hVimVzgtD6w

 

For those wary of random links, this is the late Hans Rosling presenting one of his brilliant lectures on world change in wealth, health, etc.

 

There are several others on population; e.g. explaining on why the population will continue growing (for a while) even though fertility rates have fallen below the replacement level, etc.

[swansont]

As I have heard that human populations that have a high mortality rate typically have a high fertility rate (e.g. those in Subsaharan Africa) to make up for the babies/children who will not make it to old age. I have heard that there is a natural mechanism that keeps the human population from making too few babies or too many. Is this simply not true and not the case?

 

If not, then today why are fertility rates higher in regions of the world where death rates are correspondingly high?

 

 

If there was a mechanism to prevent them from making too many we probably wouldn't have 7+ billion people in the world.

 

Fertility rates these days are high in areas that lack access to birth control (due to physical and/or social reasons), which also tend to be areas where modern medicine is not readily available. part of the higher birth rates are when the babies are dying off you tend to keep making babies so you have a family to work the land, or do whatever the family is doing. When you don't have a reliable way of not making babies when you have sex, you tend to keep making babies.

 

There are a number of studies that show that the fertility rates of immigrants are higher than the next generation, who are born in-country. There's not really anything inherent (or "natural") about this. It's more to do with all being able to make the choice not to get pregnant if you don't want to be.

 

This is one study for California

http://www.ppic.org/content/pubs/rb/RB_402LHRB.pdf

[Janus]

If there was a mechanism to prevent them from making too many we probably wouldn't have 7+ billion people in the world.

 

Fertility rates these days are high in areas that lack access to birth control (due to physical and/or social reasons), which also tend to be areas where modern medicine is not readily available. part of the higher birth rates are when the babies are dying off you tend to keep making babies so you have a family to work the land, or do whatever the family is doing. When you don't have a reliable way of not making babies when you have sex, you tend to keep making babies.

 

There are a number of studies that show that the fertility rates of immigrants are higher than the next generation, who are born in-country. There's not really anything inherent (or "natural") about this. It's more to do with all being able to make the choice not to get pregnant if you don't want to be.

 

This is one study for California

http://www.ppic.org/content/pubs/rb/RB_402LHRB.pdf

Case in point: My own grandparents immigrated in the late 1800's. My father was one of nine children born to his parents and my mother one of 11. Excluding anyone who died before having a chance to start a family (5 in total),the average number of children per family for my parent's generation was 2.2