Note that I was talking about closed ecosystems. How do you explain the specific example I gave of the dodo?
There are many other examples from similarly closed systems, such as New Zealand birds, before man (since we opened them).
I would argue that the world formerly comprised many isolated ecosystems, which have began to open over our recent history. Although the world has shrunk towards a global-village - becoming more open within - I would say most is still too isolated. It also probably takes a long time for even a fully open ecosystem to settle down, possibly on an evolutionary timescale of millions of years. But once a closed system happens to come to a stable state, it stays there (til disturbed.)
OTOH, maybe constant warfare is another point of stable equilibria?
Evolution is never at an equilibrium - it's constantly changing and experimenting through sexual recombination and mutation. So the premise doesn't hold IMHO. The dodo is an example of a species that was caught off guard in this evolutionary arms race, and was viciously exterminated by another species, namely us. Certainly there are species without natural enemies (swans, blue whales, man etc.) but they are the exception not the rule.
If evolution is constantly changing, how can a creature be caught off guard? The answer is that in a closed system, it is possible to reach a stable point that it is difficult to jump out of: in the search space of genotypes, there is a local maxima in the utility of the phenotype.
One thing I was wrong about was that the stable equilibria doesn't exist indefinitely; eventually a mutation might arise that does jump out. I was also assuming that a closed ecosystem was also closed to change in general. The latter seems more common; that equilibria is upset by an outside event that alters the utility of the phenotype - such as an open system closing, or some non-biological change in the environment (eg climate), and not by a change in the genotypes within the closed system.
It is possible that aliens are in one of these stable configurations at the time that we encounter them, which seems more likely in closed ecosystems. Closed ecosystems can be created by internal barriers being removed (which intelligent life, or at least we, seem to be doing). Of course, it's harder to eliminate change altogether (!), so that source of alteration in the utility function would remain. Yet, we certainly have motivation to eliminate environmental change that affects us adversely, so perhaps intelligent life is likely to be at equilibrium, in the long term.
If you disagree, I request that you indicate with which part. ;-)
There are many other examples from similarly closed systems, such as New Zealand birds, before man (since we opened them).
I would argue that the world formerly comprised many isolated ecosystems, which have began to open over our recent history. Although the world has shrunk towards a global-village - becoming more open within - I would say most is still too isolated. It also probably takes a long time for even a fully open ecosystem to settle down, possibly on an evolutionary timescale of millions of years. But once a closed system happens to come to a stable state, it stays there (til disturbed.)
OTOH, maybe constant warfare is another point of stable equilibria?