I am reminded of the final section of C.S. Lewis's Out of The Silent Planet, in which this whole idea of preserving the destiny of our descendents is shredded.
The introductory remarks in italics are taken from the delightful Crusty Curmudgeon.
Standing before the Oyarsa, Weston delivers a bombastic speech about the moral superiority of technological advancement and the manifest destiny of humanity to expand to the stars. However, he has so little common ground with the innocent Martians that communicating his philsophy to them proves impossible. (Fans of the Narnia books will recognize this plot device: Uncle Andrew's encounter with the talking animals in The Magician's Nephew is a recycled Weston.) Ransom, translating Weston's rhetoric into plain language for the simpler-minded Martians, strips it naked and exposes it as high-minded nonsense:
"It is in her right," said Weston, "the right, or, if you will, the might of Life herself, that I am prepared without flinching to plant the flag of man on the soil of Malacandra: to march on, step by step, superseding, where necessary, the lower forms of life that we find, claiming planet after planet, system after system, till our posterity - whatever strange form and yet unguessed mentality they have assumed - dwell in the universe wherever the universe is habitable."
"He says," translated Ransom," that because of this it would not be a bent action - or else, he says, it would be a possible action - for him to kill you all and bring us here. He says he would feel no pity. He is saying again that perhaps they would be able to keep moving from one world to another and wherever they came they would kill everyone. I think he is now talking about worlds that go round other suns. He wants the creatures born from us to be in as many places as they can. He does not know what kind of creatures they will be."
"I may fall," said Weston. "But while I live I will not, with such a key in my hand, consent to close the gates of the future on my race. What lies in their future, beyond our present ken, passes imagination to conceive: it is enough for me that there is a Beyond."
"He is saying," Ransom translated, "that he will not stop trying to do all this unless you kill him. And he says that though he doesn't know what will happen to the creatures sprung from us, he wants it to happen very much."
Weston, who had now finished his statement, looked round instinctively for a chair to sink into. On Earth he usually sank into a chair as the applause began. Finding none - he was not the kind of man to sit on the ground like Devine - he folded his arms and stared with a certain dignity about him.
More fun on this topic over at Into The Wardrobe, the most popular of the C.S. Lewis commentary sites.