sudden thought hit me: microbe populations apparently took billions of years before the next big step1 in evolution occurred: multicelled life (the first big step being cellular life in the first place; before that would be subcellular organelles. each of these took place faster.). so it's a much rarer occurence than the drake equation folks make it out to be. if it wasn't - well, shouldn't there be other occasions of newly evolving multicelled life from scratch ? and for that matter, other newly evolved cells and sub-cells, including new genetic schemes, such as (ie, non-dna, modified dna, etc.). of course, we have our usual problems recognizing new boundaries between things because of our existing patterns of recognition. and i think the classic objection to that question is that the already “more evolved” (an unsupported value judgement?) life will prevent such new evolutions through things like predation and environmental effects, etc. this is true to some extent (for example, the oxygenation of the atmosphere), but there are counter examples as well, i think. mammals, for example, were not a “better” adaptation in early times; that bias is with us now for obvious reasons.
so - where is the “new” life ? (not just the beginnings, but the current results of continuous beginnings.) ? i wonder what would happen if you isolated a place like vostok lake for four billion years - could larger life arise, (assuming the single cell variety exists) ? and consider also that any microbes have relatively recent dna encoded (as far as bacteria etc. go). perhaps different stages of evolution move through different eras of sensitivity to environmental conditions. it seems that the relation between robustness and complexity is not consistent, and perhaps sometimes an advantageous environmental bottleneck needs to occur / be traversed before life forms can evolutionarily pass through to the next robust form. luck. interesting that the human species exhibits an extreme form of robustness to the extent it's even moved off-planet, if only (briefly). and out of the solar system too, if one considers any microbes that piggy-backed on voyager, or if you just consider the probe as a mechanical expression of human existence alone - (which in turn is representative of earth life, which in turn is representative of simple universal physical laws, ...).
so they (the scientists) look at mars and europa, hoping. but if they (the planet(oid)s) did not ever experience the proper era of opportunity, and did not have anything around to take advantage of such an era, it will have amounted to nothing.
leaving aside the “new life” question, although it needs far more contemplation, i wondered about the drake equation as well, with it's handful of multiplicative terms. such an oversimplified piece of bullshit, but still, it's a starting point. i suspect the i.d. folks have something similar; i hear about their mathematical formulas that “prove” a particular pattern cannot happen by chance. (derived from what empirical observations? the works of humans ? as if we are not merely accidental ourselves. they've got a built in assumption that's the same as their conclusion. we've discussed that before - tangent here.)
so what happens if you add more or less detail into any expression ? (kinda reminds me of that roller coaster failure discussion.) ? you can take any one of the drake eqn terms and break it down into a far more complex sequence of events, things nonlinear, additive, etc. this dramatically affects the term itself, and when you consider the same operation applied to the eqn as a whole - well, you can see it for the nonsense that it is. metamath objections. now, the concept of coming up with a probability for, (and enumeration of,) life seems worthwhile in itself, even if this one attempt is flawed. well, it only seems worthwhile, until you realize that we don't even understand what it is we are working out the probability for. in fact, in our conception of life, which is so geocentric, we appear to be working out the equation for the probability of our own existence only. the only correct answer there will be “one”. duh. the answer can be anything you want, and there are no constraints on input without presumptions that poison the results. so basically, the question “how much life is out there?” is fundamentally flawed and meaningless.
now i need to get back and read the rest of the article ;-)