One limiting factor with life on a planet should be its reproduction rate.

If the reproduction rate is too fast then it would probably over populate the planet before it could become technically advanced. Think if humans were rabbits and each one of us instead of having 2.4 children per couple we have 20. The earth's natural resources would have been used up long ago.

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In a state of nature, humans have considerably more children per couple: something around 10 or 12 during the reproductive lifetime of a woman, IIRC.
As with other creatures, the effect on population growth is limited by childhood deaths (and, in the case of humans, a fairly high incidence of maternal death in childbirth, too).
So we've made (and are still making) a technological and social transition, in which improved maternal and childhood survival has gone hand in hand with a reduced reproductive rate.

One wonders if extreme r-strategists (like frogs, say) are likely to achieve technological civilizations capable of improving childhood survival, given how little quality time an r-strategist can spend passing on its own experience and knowledge to its children.

Grant Hutchison

Over last 10 years or so quite a few SF writers picked up on the idea of r-strategy intelligence. Jotoki of "Man-Kzin Wars" are like that, floaters from "Wheelers" by Cohen and Stewart, and two related species (one sentient, the other semisentient) in "Mother of Demons" by Flynn. In each case adults do not really regard newborn offspring as "creatures" - they are more like sperm to them. Only when the offspring are big enough - and natural selection culled their numbers to something manageable, - are they accepted into society and begin the process of socialization. I do not find this terribly unlikely.

A twist - both species in "Mother of Demons" feed their "pre-babies"(?) pre-digested pap in the manner of penguins, but they do it unconsciously. An adult would puke up some food and leave, paying no attention to pre-babies gathering to eat nor to predators gathering to eat them.

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Makes sense: seems like they run an r-strategy and then apply K-strategy to the "winners".
Such strategies don't seem likely to produce the explosive population growth that tommac's worried about, though.

Grant Hutchison

They could choose to protect their numerous offspring, or perhaps farm might be the better word. This would be difficult once the offspring reach maturity, as there will not be enough adults to teach them culture, leading to a state of barbarism like Lord of the Flies multiplied a thousandfold.

Unless- the species finds a rapid method of socialisation, like memory imprinting, or robotic parents to teach the young adults, or behaviour modification using automated control systems.

This sort of strategy could allow a species to very rapidly colonise a planet or system, reaching the desired level of population very rapidly; at which point the artificial culturisation mechanisms could be switched off, and the population would stabilise.

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Of course another factor that would be interesting to consider from this reproductive model, would be how the social and emotional foundations of the species would be radically different from Birds, Mammals and of course us.

With such a reproductive strategy pure chance would mean that with each generation the numbers of offspring from a single adult that reach semi-maturity could be highly variable. For example one adult might just be lucky one year and have maybe 50 of its hatchlings reach semi-maturity while another had none - all because that year it was fortunate enough to lay its eggs in a good spot where the concentration of predators happened to be low. However as this model suggests the raising and socialising of the semi-adults would be shared across the whole tribe/herd/community (choose your own collective) Thus the close genetic link between the generations found in birds and mammals and inbuilt emotional programming that is a consequence of it would be lost.

The analogy might be a messy one but in such a species the connection between the adults and those they have to socialise would be more of teacher-student connection rather than a parent child relationship. This does not mean the the adults would not care and protect the youngsters but they would not be in a position to favour their "own" children over others (a common trait among humans). Largely because for probably a large proportion of their evolutionary history they would be unable to prove which hatchling was the product of a particular parent.

Of course once their own genetic technology reached the sort of levels we are at today then that would open up their own little Pandora's box, because suddenly an unknown factor which might have been the cornerstone of their society for many generations would suddenly be swept away - there could be a sudden and for them socially unhealthy interest in their own specific genetic offspring. Who knows maybe fundamentalists within their own species might try to outlaw genetic science as it would be seen as a danger to their own social harmony.

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Reproduction rates as such tell us nothing about how many members there will be of a given species or wether the population grows or not. The typical terrestrian species did not become more numerous all the time, and there is no reason to expect the situation to be different anywhere else, due to limited ressources compared to the long lifetimes of most known species.

Hmmm yes, but successful intelligent lifeforms seem to be different. When conditions are kept artificially 'lucky', ie. medicine, agriculture, it means our number increase above the normal limits. Our gargantuan, world girdling population attests to this. Let us say a creature that has many, many young, starts inventing the above technology. How would they go about distributing the benefits? Would they wait until the ranks have been thinned down to a certain degree, until adulthood, or provide the benefits to even the least mature members. The dynamics would be very different in each case.

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We humans have been populating the planet according to our max population pressure given whatever current state of technology for some time, now. Like for the last 10,000 years.

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I am Mugs, of the Alien clan of Usa, Nordamerica, a Terran, of Sol.

Perception isn't reality. It's merely an abstraction thereof, and quite often not a very good one at that.

I am human. Fully human.

I think that if life on a the reproduction rate on a planet was very fast, the technology improvement rate would be vey fast too, just becauseit would have to be. Someone would be forced to sit down and think about it wouldn't they...?

That is one reason to encourage a high reproduction rate- with lots of new people in the world, there would be the possibility of a greater flow of ideas and of more detailed experimental and theoretical science. Also there might be proportionally more geniuses born in a crowded world or solar system; a new Einstein born every day, for example.
On the other hand the social problems from a very crowded world or solar system might be too great for this strategy to be workable.

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to believe that even what is normally seen as very slow growth can continue for very long time compared to the 5000 years history of mankind, not to talk about the perhaps 200000 years of homo sapiens presence on earth. The same may be said about life anywhere else. If the population or production doubles each 100 years it is regarded as very slow rate. In the long run that is even far too much.

Starvation, rampant disease, emotionally ravaging - all tend to force people back to basic survival mode rather quickly.

And none of which is very helpful for a technologically advancing society. That requires enough leisure time above and beyond basic survival to think hard about "what ifs?" such as "what if man could make a set of wings? Could he fly?"

We're where we are today because a few of our ancestors worked hard enough, or smart enough, to be able to store up wealth in various forms (extra food, trade goods, money, etc.) such that they had time for loftier pursuits, including pondering new ideas, inventions, and, of course, various tools.

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I am Mugs, of the Alien clan of Usa, Nordamerica, a Terran, of Sol.

Perception isn't reality. It's merely an abstraction thereof, and quite often not a very good one at that.

I am human. Fully human.

And have the time to waste to ponder 'silly' questions such as these.

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High populations with limited resources was the birth of our civilization. When one city-state had overpopulation, it either went to war or developed more efficient ways of agriculture. Either way, ideas advanced.

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