Start with concept of ecological succession. First, there is lots of open space and lights gets all the way down to ground. Taller plants develop and there is competition for light ‘up there’. Meanwhile, niches for shade-tolerant plants develop underneath. Not a complete story, but enough for now. Succession is difficult to study because timescales can be long compared to lives or careers. A simplification is called “space for time substitution”. Measure properties in areas apparently at different stages of succession and assemble a story. Imperfect, because areas may differ in ways other than successional stages, but there it is. I don’t wish to talk about all that. Instead, I wish to talk about biology of exoplanets, employing an opposite “time for space substitution”. This uses earth (only bioplanet we know) as exemplar. On earth, biology was limited to microbes for 3200 million years (my), more complex (but still aquatic) organisms for 140 my, and complex terrestrial organisms for 460 my. To date, technological civilization (by which I mean reforming metals instead of just sticks and rocks – hey, it’s a beginning!) has obtained for 0.005 my. With all of those dates being imprecise. If our pattern on earth has generality, we might expect 84% of bioplanets to have only microbes (or functionally similar local critters), 16% to have complex (but not civilized) terrestrial life, and 0.0001% to have civilizations. They who might turn their attention ‘elsewhere’ and thus possibly be findable by such as us. This is the story that earth might tell about bioplanets elsewhere. We’d be talking to one in a million (if we can). Were colonization our goal, and leaving civilized planets untouched (nobody wants a war, eh?), 16% might be turned towards our desires and 84% might seem as unplowed fields. A comparable analysis was presented by Chopra and Lineweaver (2016) in the journal Astrobiology. Alien life on most exoplanets likely dies young www.mso.anu.edu.au/~aditya/pubs/ChopraLineweaver2016.pdf Their argument was based on abiotic processes having positive thermal feedbacks (bad) and microbial processes having negative thermal feedbacks (good). Thus, microbiology can stabilize climate. After (something like) that happens, there are no guarantees that evolution on bioplanets would lead to any sort of technological civilizations. Usually it would not, they argue, just because there is no reason to suppose that it would. But see that these independent approaches lead us to similar conclusions. I have not found any Astrobiology study that flips this ecological ‘trick’ for examining exobiology. Possibly worth the effort of preparing a manuscript. Let’s see if great minds at PriusChat have any thoughts. At the same time, I’m seeking feedback from ‘published’ exobiologists not here. We shall see whether this ecological concept can cross over into those other journals. They being, in my opinion, parochial and inward-looking. But I never said so, and you never read so. Crossing (imaginary) scientific boundaries is a tricky business!
An interesting hypothesis: This suggests if our species is going into 'terra forming,' we'd be best advised to become DNA artists. Step one, assemble single cell biologics who can survive on the existing planet and begin converting the planet into a positive feedback, thermally safe environment. Of course that begs a question. Will our species survive our current efforts to increased greenhouse gasses? Bob Wilson
The thesis of Humans are not from Earth is that humans were deposited on Earth from somewhere else. The 600+ pages cover quite a variety of scientific references about how we are more designed for other places than Earth. Things like we are designed as herbivores, but chose to eat meat. Our genomes have scars indicating editing, unlike other primates. The humanoid footprints among the dinosaur tracks are real, but indicate a line of humans deposited back then but since gone extinct. Evolution is real, our part in it just started somewhere else.
When I was in school, I would speculate about whether I was being punished for some forgotten sin by being condemned to earth. Bob Wilson
Not from Earth@5. Discussion of panspermia is long and varied. This book may represent a much narrower view, that only one or few primates are 'exo'. If one or more ET are similar enough to earth humans to 'pass' here, that would seem evidence in favor of some prior civilization doing placements. Chance that fully independent evolution on different planets would lead to such similarity seems small to me.
Illusion @3. Hypotheses are supported by evidence, or refuted. This one is not yet in either category. I'd prefer not to call any of them illusory. == Further thoughts on original. Might be better to include all 3 planets approx. in what we call Sun's habitable zone. Evidence accumulates that Mars had (simple) biology long ago. Venus is vexing, with a very well autoclaved surface. Something may show up in upper atmosphere when dirigibles arrive there. Giving Venus the benefit of doubt, extend further to suggest that hab-zone planets with water routinely become biotic. Two-thirds of them lose it at single-cell stage. Divide all other estimates in top post by 3. This hypothesis is doomed to rattle about until we can 'scope' atmospheric chemistry on other hab-zone planets. == Presenting ideas way before their time is a fragile but not always futile bid for immortality. May not even matter whether eventually supported or refuted. On one hand, Catholic Priest George Lemaitre 'gets a wiki' for anticipating Big Bang. On the other, Patrick Zimmerman published (in Science) an estimate for methane production in termites. It turned out to be wildly high. That article has been cited a huge number of times by others essentially saying "you guys were so wrong". Ah fame - a sword with two sharp edges.
Punished? More like being a lab rat in some post doc's experiment. We seem to be designed on a 25 hour cycle, dumped into a 24 hour environment. Was that an oversight, or the object of the experiment? In any case, we are designed with a case of chronic jet lag. And what's with these seasons? We're maladapted to 2 of the 4 seasons. And the sun's too bright. If we evolved here, we wouldn't have any of these problems.
Maybe so, or maybe not. If you're a dyed in the wool evolutionist, you've got to discredit or ignore evidence selected by the creationists. Maybe the archaeological evidence is correct, and they're both right. Distant origin accommodates both sides. Dr. Silver points to evidence that humanoids popped up in at least 6 different area of Earth that aren't related. The first 5 didn't survive. Maybe we needed the dinosaurs to play out before our species could survive.
A friend mentioned the other day that they are seeing seasonal variations in the methane the Mars probes are recording. Curiosity rover sees seasonal Mars methane swing - BBC News
discredit or ignore evidence@12. May regret asking this - what specific evidence and published where? We could discuss where and when all (as of yet) known species in genus Homo existed. I am sure that some gaps exist. Whether it is more parsimonious to attribute this to not-yet-discovered fossils, or ET 'seeding', is apparently an open question. Dinosaurs as such dropped out ~65 million years ago. Genus Homo seemed to have diverged from more distant relatives < 3 million years ago. Length of that gap seems to argue against a strong 'H only if not D' statement. So it seems to me.
