# Population control problem:

sonhouse
Posers and Puzzles 03 Jul '14 21:40
1. sonhouse
Fast and Curious
03 Jul '14 21:401 edit
So a virus hits the human race, all of them world wide and the result is only 1/3 of the people can reproduce.

So 100 years or so after the virus hits, the population is down to 900 million.

300 million reproducers and 600 million steriles.

So how many kids do the reproducers have to have to keep the population at 900 million, assuming that same ratio of sterile V reproducers comes out in the progeny?

The same virus also gives people longer life spans, they now live an average of 200 years. Does that make a difference?
2. Ponderable
chemist
04 Jul '14 10:39
Originally posted by sonhouse
So a virus hits the human race, all of them world wide and the result is only 1/3 of the people can reproduce.

So 100 years or so after the virus hits, the population is down to 900 million.

300 million reproducers and 600 million steriles.

So how many kids do the reproducers have to have to keep the population at 900 million, assuming that same ra ...[text shortened]... es people longer life spans, they now live an average of 200 years. Does that make a difference?
1. Assumption: All reproducers reproduce. (this need not be the case if you would have strict laws on marriage or a lot of unmarried and unpartnered people.

Then to keep the population constant each reproducer has to have six offspring: Two fertile, which count half to each partner in terms of replacement, and four infertile to keep the numbers.

The actual age is not really important as soon as an equilibrium between birth and detah rates has been achieved.

The age of fertility might play a role if we assume each female to have six births, which is a quite larger number.
3. sonhouse
Fast and Curious
04 Jul '14 15:58
Originally posted by Ponderable
1. Assumption: All reproducers reproduce. (this need not be the case if you would have strict laws on marriage or a lot of unmarried and unpartnered people.

Then to keep the population constant each reproducer has to have six offspring: Two fertile, which count half to each partner in terms of replacement, and four infertile to keep the numbers.

The ...[text shortened]... y might play a role if we assume each female to have six births, which is a quite larger number.
Ok, I thought it would be more complicated. I didn't know the answer, just set up this situation for a possible Sci fi plot.

Of course those numbers would be the average. I suspect if a situation like that actually happen, the remaining fertile women would be more than happy to have as many children as needed. 6 kids is a lot for sure but look at the women with 9, 10, 11 kids! Pumping them out once a year for a decade.
4. DeepThought
06 Jul '14 19:57
Originally posted by sonhouse
Ok, I thought it would be more complicated. I didn't know the answer, just set up this situation for a possible Sci fi plot.

Of course those numbers would be the average. I suspect if a situation like that actually happen, the remaining fertile women would be more than happy to have as many children as needed. 6 kids is a lot for sure but look at the women with 9, 10, 11 kids! Pumping them out once a year for a decade.
You've never met any feminists have you?
5. 07 Jul '14 12:311 edit
Originally posted by sonhouse
Ok, I thought it would be more complicated. I didn't know the answer, just set up this situation for a possible Sci fi plot.
You may want to read Dan Brown's latest novel.
6. wolfgang59
Mr. Wolf
10 Jul '14 01:24
Originally posted by sonhouse
So a virus hits the human race, all of them world wide and the result is only 1/3 of the people can reproduce.

So 100 years or so after the virus hits, the population is down to 900 million.

300 million reproducers and 600 million steriles.

So how many kids do the reproducers have to have to keep the population at 900 million, assuming that same ra ...[text shortened]... es people longer life spans, they now live an average of 200 years. Does that make a difference?
If only 1 in 3 can reproduce and couples marry for L O V E
(rather than having kids) then only 1 in 9 couples would
reproduce; requiring that on average fertile couples have 18
children just to keep the population stable!!!!
7. sonhouse
Fast and Curious
11 Jul '14 17:47
Originally posted by wolfgang59
If only 1 in 3 can reproduce and couples marry for L O V E
(rather than having kids) then only 1 in 9 couples would
reproduce; requiring that on average fertile couples have 18
children just to keep the population stable!!!!
Why wouldn't it be one in 6 couples having kids? If 1 in 3 can reproduce, then 2 of 6 can reproduce. I would suspect there would be a mandate for reproducables to have a lot of kids.
8. sonhouse
Fast and Curious
11 Jul '14 17:484 edits
Originally posted by Fanakick
You may want to read Dan Brown's latest novel.
What is that novel? Is it about the situation I played out here?

Do you remember that old movie called A boy and his Dog? He got into a situation where he was forced to have orgasms hooked up to a machine to collect his sperm. From a novella by Harlan Ellison. 1975.

Never mind, I googled it, WW2 novel. Bad times for sure but not as bad as the entire world going 2/3 sterile.
9. 11 Jul '14 21:47
It's not about WW2, I don't know where you got that information from.

http://en.wikipedia.org/wiki/Inferno_%28Dan_Brown_novel%29

It's about a maniac who tries to create a kind of a virus which sterilises 1/3 of the world (to solve its population problem).
10. wolfgang59
Mr. Wolf
14 Jul '14 11:15
Originally posted by sonhouse
Why wouldn't it be one in 6 couples having kids? If 1 in 3 can reproduce, then 2 of 6 can reproduce. I would suspect there would be a mandate for reproducables to have a lot of kids.
No.
For every 9 men, 3 are fertile.
For every 3 fertile men, 1 is paired with a fertile woman.
So 1 in 9 are fertile couples.
11. Ponderable
chemist
15 Jul '14 10:02
Originally posted by wolfgang59
No.
For every 9 men, 3 are fertile.
For every 3 fertile men, 1 is paired with a fertile woman.
So 1 in 9 are fertile couples.
The assumption I wrote about was that there were no moral boundary conditions, such as strict marriage.

If the aim of the society was that they keep population constant they would probably encourage promiscuity for the sake of creating offspring ...
12. wolfgang59
Mr. Wolf
19 Jul '14 04:22
Originally posted by Ponderable
The assumption I wrote about was that there were no moral boundary conditions, such as strict marriage.

If the aim of the society was that they keep population constant they would probably encourage promiscuity for the sake of creating offspring ...
Yes you were correct.
I was making the comparison if couples married for L O V E.