Re: population growth

Sorry for the resend, I sent it this morning and it still hadn't shown
up.

 >>>>>>>>>>>>>>>>>>

G'day guys,

Laserlight asked:
 > Let's say the colony Hypothetica starts off with 1 million
 > colonists in 2070.
 > Large families are highly valued so each couple has 8 children
 > --1 every 2.5 years starting at age 20 (and we'll assume all
 > colonists are 20 when they arrive and none have their own kids).
 > The incidence of twins, triplets, extra kids above 8, etc,
 > cancels out the effects of infant mortality.
 > Everyone lives to be 80.
 > Immigration after initial colonization is negligible.
 >
 > How many people are there in 2190?

Assuming no war, famine, accidents, disasters, reproductive break
throughs 
or immigration, then most likely between 7.5 and 9 million depending on 
social welfare policies.

Karl commented:
 >Moving one million people is no mean feat.

Very true. Though the biggest hurdle is getting them into space in the 
first place I'd say. The space elevator Kim Stanley Robinson uses has 
probably been the best mechanic used to get around the problem I've come

across in my limited scifi reading (I know he didn't think it up he's
just 
the only one who's used it in a book I've read).

 >Sustaining such extreme population
 >growth over such a long period will
 >be very hard.

Exceedingly difficult to keep up for more than a few generations if our
own 
history is any indicator. However, this is assuming that no state run 
system comes into play.

 >Will agriculture, schools, health care, general
 >infrastructure be able to keep up ?

Not everywhere, but in some spots I could see the governors letting some

slide to concentrate on others, funnel people into labour intensive jobs

and away from higher education for instance.

 >AFAIK, all historical human populations had either lower life
 >expectancies or lower birth rates than those assumed above.

4% growth is VERY high for a human population. On the flip side there's 
still a lot of argument on longevity, if you can beat
childhood/adolesence 
then you quite often stand a chance of being in the 70s and maybe low
80s 
regardless of what era you were born in.

Tom's turn:
 > I can see the models that some
 >people subscribe to differ
 >significantly and assume a far
 >higher level of population growth
 >through mass emmigration.

As a side note, Derek and I opted to lean towards the high side (not 
through emigration but mostly social attitudes and medicine) in our 
parameterisation of the OU modelling as it gave more scope for a
military 
large enough to justify having the figs Derek wanted within the
timescale 
Jon had laid out.

 >1) I looked at the economics in FT
 >of shifting large masses of people
 >(enough to make a difference of say
 >1% to Earth's population). The amount of
 >ship mass required even with
 >unsanctioned packing densities is still
 >outrageous.

Do you mean economics or logistics?

 >2) I base my conclusions on Earth as
 >not overpopulated (necessarily)

For those that are interested there's three routes the UN population 
modellers can currently see (I think I may have said this before but
I'll 
ramble forth again anyway):
A. Growth at levels of the mid to late 80s which would see us hit 50 
billion in the 2100s. Current growth suggests that this is not going to 
happen and of the three paths its now considered the least likely.
B. Growth levels out at about 15-20 billion or a bit below and then 
stabilising a little lower still (now favoured). This is based on
current 
growth which sees the African nations dropping quickly (both in birth
rates 
and due to AIDS), Asia not growing as quickly as it used to and the
western 
nations either at a standstill or turning negative growth wise.
C. We hit 9 to 10 billion, many of us die off (just from old age
alone... 
imagine the drop China's going to see in the next 30 yrs), birth control
is 
entrenched and we actually see a global down turn with a population of
only 
3 billion when the dust settles (governments would be actively
encouraging 
large families to support their established economies). Not the highest
on 
the list of possibilities but actually more likely than the 50 billion 
scenario the last time I checked.

So all up the UN reckon there will most likely be between 6 and 35
billion 
people on Earth in 2100. Derek and I based ours on about 17 to 20
billion 
(it'd be tight but doable with some of the technologies cropping up, 
there'd still be a lot of social unrest though I reckon).

 >3) Increasing life spans and
 >economic prosperity kill birth rates.

More than anything the education of women does. How to women feature in
the 
future history? That would be the best indicator of what's happening on
the 
natural reproductive front (doesn't account for clones, artificial wombs

etc though).

 >Even in the colonies, it won't necessarily
 >be economically expedient to have 8 children
 >in 2183.

That depends on how widely spread machinery is and whether they're in a 
dome city or can walk freely beneath the sky. If free then they may well

have large families to keep up the cheap labor supply as the older ones 
move next door to start their own farm. It don't matter to Joe if fancy 
farming robots exist if he can't afford one, but his kids work for
peanuts 
(or potatoes or whatever other crop they grow).

 >The cost of protecting those shipments
 >from your enemies would be back breaking.

If you protected them and if they were in operation when hostilities
abound.

 >And only the ESU and a few others
 >could do it "against the will" of the settlers.

I don't know I reckon the odd penal colony could still take off here and

there... out of sight out of mind worked before, could work again, but
that 
make be a biased Aussie view ;)

 >My suggestion is Earth's population is 6-9 Billion
 >(maybe 10-11 if we want to assume some crowding).

Not too bad, though I'd still push a little higher just to let everyone 
have their minor nation with ships and fighters ;)

 >I'd suggest off-Earth population all together
 >totals no more than 25% of the on-Earth figure.

I haven't had a go at modelling the entire GZGverse as yet <I was
leaving 
that for you Tom ;)> but I'd say that'd be on the high end of things,
20% 
or less would be closer to what I would've said.

 >Beth, you must have something to say
 >and some work to procrastinate....

You're encouraging me to ramble Tom? You do realise how dangerous that
is? 
Besides some excuse it'd make for my supervisor "Well the reason the
next 
chapter isn't ready and waiting on your desk was that I was endeavouring
to 
calculate the percentage of the human population off earth in 2190..."
;)

Have fun

Beth

------------------------------------------------------------------------
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Elizabeth Fulton
c/o CSIRO Division of Marine Research
GPO Box 1538
HOBART
TASMANIA 7001
AUSTRALIA
Phone (03) 6232 5018 International +61 3 6232 5018
Fax 03 6232 5053 International +61 3 6232 5053

email: beth.fulton@marine.csiro.au