Even if somebody else has already remarked it: What is the evidence from which we could conclude that "Single planet species don't last?" Obviously there were many species that have died out; equally obviously, there were many species that have not died out, namely those species that are with us today. Some of them have been around pretty long - think of some types of insects. If more species may have died out than are with us today, then we can just hypothesize that "Many single planet species don't last." We could belong to the more lucky group. The fact that no species has been around all the time bears no significance here.
Slashdot Mirror
Even if somebody else has already remarked it: What is the evidence from which we could conclude that "Single planet species don't last?" Obviously there were many species that have died out; equally obviously, there were many species that have not died out, namely those species that are with us today. Some of them have been around pretty long - think of some types of insects. If more species may have died out than are with us today, then we can just hypothesize that "Many single planet species don't last." We could belong to the more lucky group. The fact that no species has been around all the time bears no significance here.