Originally Posted by ZONA
Very well put. That is exactly correct. And just to add one more thing, each species is on a time clock right from the go. Use mankind as an example. As you said, we were not even the first species on this planet. By the time we came around, our Sun was already through half of it's life. And our Sun is about the perfect type of star for life to evolve. Many other stars are much bigger and burn out even faster, giving said species even less time to evolve and develop advanced technology. Then you also have the life term of the planet itself. Take Mars for example, it's believed to have had an atmosphere long ago. It's just that the planet being further away from the Sun and smaller then Earth, it's core cooled much faster, making it unable to sustain it's atmosphere. So any other living creatures on some planet far far away have to advance pretty quickly or their chances at developing technologies to sustain them through space travel become highly unlikely. Then throw in random astroid collisions and many many other things that can destroy all life on a planet, you have to get pretty lucky I'd say. Venus is another good example. It's in the so called "habital zone". It just had too much water vapor in it's atmosphere early on, which caused a major greenhouse reaction that just snowballed and now it's a furnace with atmosphereic pressure that is 10 times that of Earth. We have perfect examples right here in our own solar system that show us, plenty of things have to go just right for a species to live and thrive.
True, there are examples in our system of how hard it is for life to Develope, and there is a timeline for each age that is a window of opportunity..
But you also need to look at Tough it is to kill ALL life on a planet. The Earth has had many extinctions in its history, but life always came back. Our species has developed in just the last 4 million years from a primate that was just starting to stand upright to where we are now. On the Cosmic scale that is but an eyeblink, a millisecond. In the last 10,000 we have gone from
stone age tool users to nuclear capable (most of it in the last 5000). Prior to that there was an ice age, so significant historical finds past that age are obscured and lost, but the thing is even we homo sapiens survived that period, in fact that is when we became dominant.
Our speed of development may be unusual , or it may be normal. I tend to think we are unusually fast, but that may be a result of the fact that we live on an active and changing planet. It may be that it is a necessity to have such a planet in order for evolution to be spurred to produce a species like us.
The dinosaurs ruled the planet for 50 million years. Their extiction by a planet killer comet led to the rise of the mammals as dominant life form (on Land) due to the power vacuum at the top of the food chain. Life is incredibly capable of adapting to extreme conditions. Sentient life is probably extremely rare, yes, but also the only one capable of Purposely
spreading itself beyond its planet of origin. If we, as a species, can survive the next 1000 years I have no doubt that we will have established self sufficient colonies off this planet. Once that is done it then gives us the time to even modify ourselves through genetic engineering to be adapted to live in different environments that no base line human could survive in. Once that threshold is reached the timeline of developement is no longer a factor. Sentient life that reaches space and gets out of the "cradle" of its home planet is no longer limited.
And then the Stars are the limit!