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- There’s the one I just mentioned. According to Wikipedia when Frank Drake first proposed his equation, his guess for the fraction of stars with planets was ½. After looking at the data from Kepler, our current estimate is basically that all stars have planets. Our uncertainty decreased and it moved in the direction of extraterrestrial life and civilizations being more probable.
- I also talked about number of rocky planets, which relates to the term in the equation for fraction of total planets which could sustain life. As I mentioned above we used to think that rocky planets would only appear seven billion years or so into the lifetime of the universe. Now we know that they appeared much earlier. Once again our uncertainty decreased, and it went down in the direction of life and civilizations being more probable.
- Finally there’s the existence of extremophiles. We used to think that there was a fairly narrow band of conditions where life could exist, and then we found life in underwater thermal vents, in areas of extreme cold and dryness, in environments of high salinity, high acidity, high pressure, etc. etc. Yet another case where as we learned more, life became more probable, not less.
- Certain things double every so many years. The most famous example of this phenomenon is Moore’s Law, which says that the number of transistors on an integrated circuit doubles every two years. A while back some scientists wanted to see if biological complexity followed the same pattern. It did, doubling every 376 million years. With forms of life at the various epochs fitting neatly onto the graph. The really surprising thing was that if you extrapolate back to zero biological complexity you end up at a point ten billion years ago. Well before the Earth was even around (or Mars for that matter). Leaving Panspermia as the only option. Now the authors confess this is more of a “thought exercise” than hard science, but that puts it in exactly the same category as the paper which “dissolves the Fermi Paradox”. (I would actually argue that the Moore’s Law analogy is probably less speculative.)
- There’s a significant amount of material travelling between planets and even between star systems. I mentioned this in a previous post, but to remind you. Some scientists decided to run the numbers, on the impact 65 million ago that wiped out the dinosaurs. And they discovered that a significant amount of the material ejected would have ended elsewhere in the Solar System and even elsewhere in the galaxy. Their simulation showed that around 100 million rocks would have made it to Europa (a promising candidate for life) and that around a 1000 rocks would have made it to a potentially habitable planet in a nearby star system (Gliese 581). Now none of this is to say that any life would have survived on those rocks, rather the point that jumps out to me is how much material is being exchanged across those distances.
- Finally, and I put this last because it might seem striking only to me. I came across an article recently that said the very first animal had 55% of the DNA that humans have. They ascribe this to an “evolutionary burst of new genes”, but for me that looks an awful lot like support of the first point in this list. The idea that life has been churning along for a lot longer than we think, if the first animal had 55% of our DNA already half a billion years ago.