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#1 2012-03-06 13:57:55

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
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Minimum Growth

An advanced civilization can grow at a very small exponential growth rate and sill have significant growth but an initial colony has to as a minimum replace the old generation. A generation is considered to be roughly about 20 years and without new births in that time period the population will begin to stagnate. If each couple had two kids and started having kids at 20 then an initial population of 2 would grow to about 8 over a period of 80 years but if the growth rate does not exceed that the population will cease to grow as the death rate begins to match the birth rate.

Consequently an initially guess would be that between 3-4 kids per couple would be necessary to have a reasonable successful chance at growth. On a large scale initial mission 8 people, we will have a population of 8 initial people  4 generations x 4 kids per couple / 2 people per couple =126 people
Which is on average a growth of 1.6 people per year for a period of 80 years.

Last edited by John Creighton (2012-03-06 13:58:39)

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#2 2012-03-06 18:55:03

louis
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From: UK
Registered: 2008-03-24
Posts: 6,918

Re: Minimum Growth

John Creighton wrote:

An advanced civilization can grow at a very small exponential growth rate and sill have significant growth but an initial colony has to as a minimum replace the old generation. A generation is considered to be roughly about 20 years and without new births in that time period the population will begin to stagnate. If each couple had two kids and started having kids at 20 then an initial population of 2 would grow to about 8 over a period of 80 years but if the growth rate does not exceed that the population will cease to grow as the death rate begins to match the birth rate.

Consequently an initially guess would be that between 3-4 kids per couple would be necessary to have a reasonable successful chance at growth. On a large scale initial mission 8 people, we will have a population of 8 initial people  4 generations x 4 kids per couple / 2 people per couple =126 people
Which is on average a growth of 1.6 people per year for a period of 80 years.

I don't feel you've thought this through entirely.

1. As long as you have a source population, you don't need procreation to increase your population.  Monastic colonies are examples of colonies that don't rely on procreation to grow.  Other colonies (not such a nice example) such as the slave societies of the Caribbean grew exponentially as a result of importation of people.

2.  You first have to address the issue of embryo development. There is good reason to believe that one third  gravity will not be conducive to good embryo development. Furthermore, pregnancy will be v. resource intentive in terms of medical equipment for an infant community.

3. Wouldn't it be better to simply rely on adult incomers to grow the colony to begin with, with people gradually increasing their period of stay as we learn more about one third gravity.


If we can get to the point where in situ procreation is a real option, the colony might face an issue over encouraging women to have larger families.  I have suggested before that  the colony might want to encourage women to have two children early on - e.g. in their early 20s, followed by two more when they are in their late 30s.  You would need to have Kibbutz style child care arrangements as well I think.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#3 2012-03-07 13:58:59

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
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Re: Minimum Growth

louis wrote:

I don't feel you've thought this through entirely.

In most things that are interesting it is impossible to think the topic through entirely.

1. As long as you have a source population, you don't need procreation to increase your population.  Monastic colonies are examples of colonies that don't rely on procreation to grow.  Other colonies (not such a nice example) such as the slave societies of the Caribbean grew exponentially as a result of importation of people.

I think this will be more costly though.

2.  You first have to address the issue of embryo development. There is good reason to believe that one third  gravity will not be conducive to good embryo development. Furthermore, pregnancy will be v. resource intentive in terms of medical equipment for an infant community.

I have no way of testing this at this time so I have to make assumptions.

3. Wouldn't it be better to simply rely on adult incomers to grow the colony to begin with, with people gradually increasing their period of stay as we learn more about one third gravity.

This would be a more costly approach in that it is money spent which is not spent to towards the direct achievement of our goals.

If we can get to the point where in situ procreation is a real option, the colony might face an issue over encouraging women to have larger families.  I have suggested before that  the colony might want to encourage women to have two children early on - e.g. in their early 20s, followed by two more when they are in their late 30s.  You would need to have Kibbutz style child care arrangements as well I think.

That would give the four kids I suggested. I don't know much about Kibbutz. Maybe post about how it might relate to mars in another thread.

Last edited by John Creighton (2012-03-07 14:00:03)

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#4 2012-03-07 17:28:24

louis
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From: UK
Registered: 2008-03-24
Posts: 6,918

Re: Minimum Growth

John Creighton wrote:

I think this will be more costly though.

I don't know why you think that. Raising and educating non-productive children is very costly. They need teachers and doctors. Women in their final trimester are not very productive.  On Mars they will probably have to go into an artificial gravity environment for several months of their pregnancy  to ensure normal embryo development. In addition pregnancy itself will require much more investment in medicine and health facilities.  Why go to all that expense in the early decades?

You say "This would be a more costly approach in that it is money spent which is not spent to towards the direct achievement of our goals."  I can agree that the creation of a fully functioning human community on Mars is the objective and that must include procreation in due course. But let's not run before we can walk. Let's create the society that can support pregnant women and young children and let's learn all we need to know about embryo development in third gravity before we try it. 

I think the Kibbutz are quite relevant. They were essentially moneyless mini-economies (often under 200 people)  where everyone was dedicated to a common goal and they tried to be self-sufficient in what was often a hostile environment.

The Mars colony will naturally have a common objective I think, simply because of the people it will attract. I think the early Mars colony will be a cross between an Antarctic research station, a Kibbutz, a mining camp and a university campus.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#5 2012-03-07 20:15:39

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
Website

Re: Minimum Growth

louis wrote:
John Creighton wrote:

I think this will be more costly though.

I don't know why you think that. Raising and educating non-productive children is very costly.

So is sending people to mars. I'll reply to the rest later.

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