Population Growth Help

[danzig138]

Hello,
I need some help for something I'm working on. I need to know roughly how much a population would increase in 100 years, from a base of 138, with 21 viable child-bearers. The colony has good resources, no immigration, and little attrition. I'm not good with the required math. Thanks in advance.

 

[Xeriar]

You can go crazy with this, and you sort of have to do some here. Because while you can start out with a 10% population growth rate, you won't be ending up there at the end of those 100 years (2 million people!)

A straight 2% growth rate leaves you with a population of 999.76 (hehe). Would suggest a pretty strong starting community, though. 1% leaves you with 373 and is probably more realistic for a good area and starting population that isn't phenomenal.

There are more complex methods, but they are time consuming and require a lot of work to get things right. My method is to pick overall growth, (between .5 and 2.5%) and perform the exponent rule on it (1.01^100 for example) and multiply by the original population.

 

[Umbran]

There are many variables....
You say there's "little attrition". By this, can we assume you mean that nobody dies, even of old age?

At what age do these people feel a woman is ready to have children? 15? 20? This can drastically affect the results.

How many children does each woman have, on average? This is both a matter of resources and culture.

Let us assume 138 adults. 21 women who can have children. Half of all children are female, all females born are capable of bearing children. Absolutely nobody dies, for any reason.

If each woman has two kids... If generation time is 20 years, you end up with something like 350 people, 42 of which are infants. If generation time is 15 years, you end up with more like 390 people, 42 of whom are adolecent.

If each woman has three kids...If generation time is 20 years, you end up with roughly 970 people, 320 of which are infants. If generation time is 15 years, you end up with more like 1450 people, 477 of whom are adolescents.

Those are rough numbers, but they illustrate the point. The generation time and number of children per family makes a big difference.

 

[danzig138]

There are many variables....
You say there's "little attrition". By this, can we assume you mean that nobody dies, even of old age?

Many of the original population will die of old age with a couple of decades. Women are considered ready for bearing children at 14-15. As a whole, the people are concentrating on increasing their population, using the "it takes a village" idea, so the women are encouraged to have as many children as possible until their bodies just can't do it any more.

 

[Xeriar]

Many of the original population will die of old age with a couple of decades. Women are considered ready for bearing children at 14-15. As a whole, the people are concentrating on increasing their population, using the "it takes a village" idea, so the women are encouraged to have as many children as possible until their bodies just can't do it any more.

You don't really give enough information. What's the level of health in the town? Is there something capable of reducing the atrocious infant mortality rate?

Regardless, if that is the intent, the limit is not the original area so much as what is the area capable of supporting.

I modelled a population of about 2,700 for a thriving area, but that's assuming that they don't have anything that can keep mortality rates down.

 

[danzig138]

Except for the older folks, the level of health is pretty good, but they lack clerical spells to remove diseases and such. There really is no way of reducing infant mortality. The land is good, near a body of water, with room to expand, , and capable of supporting a large population.

 

[Xeriar]

Except for the older folks, the level of health is pretty good, but they lack clerical spells to remove diseases and such. There really is no way of reducing infant mortality. The land is good, near a body of water, with room to expand, , and capable of supporting a large population.

Seriously, if there isn't any threat to their growth, or any social limiter to the 'push out more kids' routine, and they got a good genetic mix, they could be able to maintain a ~5% annual growth rate. The land has to be pretty expansive, and there better be some brilliant city planner, and a great way to move food, fuel and waste around. That leaves you with about ~18,000 people.

Something more realistic drops this to an overall ~4% (actually, a gradual reduction in population growth rate), that leaves you with a population of 6,905. This is still pretty darn exceptional, would have to be a divine mandate, or something.

 

[Tonguez]

A Real Example

My Grandmother is 91 years old (my grandfather unfortunately died in 1969)

They now have almost 400 descendants, reaching to 6 generations (ie a great-great-great grandchild) at the last count there were 367 of us (not counting stillborn children) and since then I know of at least 4 additional births

Anyway my grandparents had 19 children (my father being 13th), 17 had children of their own (2 died in Infancy) and on average they had about 7 children each

If we assume that something like 100 of the 400 have died then we get 300 descendants of a single pair of 'Parents' or a 1500% growth...

something to think about

 

[kengar]

Re: A Real Example

My Grandmother is 91 years old (my grandfather unfortunately died in 1969)

They now have almost 400 descendants, reaching to 6 generations (ie a great-great-great grandchild) at the last count there were 367 of us (not counting stillborn children) and since then I know of at least 4 additional births

Anyway my grandparents had 19 children (my father being 13th), 17 had children of their own (2 died in Infancy) and on average they had about 7 children each

If we assume that something like 100 of the 400 have died then we get 300 descendants of a single pair of 'Parents' or a 1500% growth...

something to think about

WOW! That's amazing! If I read that correctly, you are potentially (within your family tree) a GREAT-GRANDPARENT! And a gamer!

 

[danzig138]

Re: A Real Example

They now have almost 400 descendants

Dang. A family of, to use Vince McMahon's words, "genetic jackhammer" (s). I'm pretty sure my family doesn't have numbers anywhere near that. Anyway, I've decided on about 6,000 for my population. It's lower than I wanted, but seems more reasonable to me. Thanks for the help.