Isn't The Great Filter something in the Whatman catalog?

Twice in the last week the Globe has run pieces on a concept called 'The Great Filter', once on the Op-Ed page and now in the Star Watch astronomy column. I've read both, and the pseudo-statistical thinking in them just irks me.

The headline on the star watch column suggests the hubris that is perhaps what is goading me: "Why a microbe on Mars would change humanity's future". I'd completely agree that discovering microbial life on Mars would be exciting, but where it goes from there is bizarre.

The gist of the argument can be found in this quote

If life arose independently twice in just one solar system, it would mean that the life formation process is easy and common. Life would be abundant everywhere. Most starts have planets, os the entire universe would be teeming with living things.
Good news? No. The chance for humanity's long-term survival would immediately look worse.
Follow carefully now. Whether or not simple life is common, we know that intelligen, technological life -- like us -- is probably rare. Otherwise, goes the arugment, it would have noticed such a good planet as Earth and come here to colonize as early as hundreds of millions of years ago

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Given that we haven't yet found signs of other advanced life (or any life) elsewhere

If life is common, something apparently stops it from developing to the point of gaining interstellar travel and settling the galaxy...Apparently, some kine of "Great Filter" preveents life from evolving to the point of getting starships. If the Great Filter lies early in evolution -- such as if the origin of life itself is a rare fluke -- then we, humanity, have already gotten through it. If the Great Filter lies ahead of us -- such as, for instance, if technological civilizations always destroy themselves as soon as they get to power -- then we have no more chance of making it than all the others who have failed and left the cosmos silent.
The more advanced the fossils of living things that Mars may hold, the greater the chance that the Great Filter lies not behind us but ahead.

Okay, just where to start. First, the current Mars mission finding life on Mars is a far cry from finding that life arose independently on Mars. We know that rocks make the transit occasionally, and while we think we sterilized all the probes, the possibility that any life form found really shares a common heritage must first be ruled out. Gary Ruvkun has suggested an experiment for a future probe to look for & sequence ribosomal RNA (if I remember correctly); that would be an appropriate follow-up.

There's also the problem of an N of one: Mars is one planet. Maybe you count an N of 2 with Earth as the second case, though since you're trying to predict on it that's a case of training on your test set. Mars is hardly an independent sample; the same solar system, which may or may not have some unusual properties.

But perhaps more irksome is conflating the reasonable idea that there are difficult barriers against spacefaring species to arise with the rather silly one that there is a single "Great Filter". Mars is a particularly poor example, as we would have a good guess what the filter is there: the planet quit being a nice place to live.

How improbable is life? How often do planets get life but it stays unicellular? How often multicellular but never ambulatory, sentient beings? How often do those sentient beings come up with some way to prevent travel to the stars -- a religion that forbids it, self-extermination (which our species has toyed with). Perhaps some inhabited planets have a super Van Allen belt which dissuaded their residents from becoming star travelers. Perhaps there are intelligent cultures far away -- but with a timing such that their signals can't yet reach us.

The fact is, any estimates of the probability of any one of these (or anything else you can imagine) are nothing but personal priors, wild guesses without much basis in fact. Feel free to make them, but spare us the headlines about predicting doom and gloom.

Space, the final bio-frontier?

In case it hasn't been obvious from the occasional post, I am a spaceflight aficionado. As a very young child I watched some of the last moon landings. Many hours of play were spent imagining riding a rocket, playing with toy rockets, and building Lego spaceships.

At some point I realized I really didn't quite have the Right Stuff. Clearly I was never going to cut it as a pilot (I carry scale models of Hubble's corrective lenses on my nose daily), and in the end my scientific interests weren't really going to support traveling to space. So it became purely an observational hobby, though the dream has been rekindled a bit by the notion of buying a rocket ticket (alas, 2001 has come-and-gone without the vision of 2001). When Millennium changed travel agents a few years back & we needed to fill out new travel preference forms, I put Virgin Galactic as my preferred carrier.

A more inner struggle, one reflected in much of the space community, is the appropriate role of humans in space, or perhaps more pointedly, of government funding of humans in space. It is one thing for some gazillionaire to pay multi-millions to take a joy ride (anyone want to spot me $50M for a week PLUS a spacewalk?); it's another for governments to continue to spend billions to put people up there. Manned flight is thrilling, but robots tend to get more data.

An item in The Scientist (free registration may be required) points to this debate again, and close to my scientific home. Lobbying is firing up again for biology research in orbit, and given that the company (Spacehab) lobbying for it builds manned research gear, they're pushing the manned angle.

Space research has yielded many earthly benefits, but they're mostly in areas such as communications & remote sensing. It is difficult to really prove a case for very many other areas. Spaceflight remains rare, unpredicable & expensive, three qualities that few like to associate with their research programs.

Two biotech claims are advanced to support space research. One is the long-standing issue of crystallography -- the claim is that crystals for X-ray diffraction studies can be grown in space that are either higher quality than ground samples or which simply can't be made on the ground. The other is a very new claim of vaccine research.

If anyone knows of a good, balanced (not in the Fox News sense!) review of space-based crystallography, I'd love to have a pointer. I'm not in that community, but my general impression is that while useful data has been collected on space-grown crystals, it really hasn't taken that community by storm. Perhaps if flights were cheap & frequent it could, but other approaches such as high-throughput condition screening have had a bigger impact.

The vaccine claims are based on a paper published last year in PNAS (also covered in The Scientist) which found that spaceflight changed some key gene expression programs in Salmonella and that the space-flown bugs were more virulent. A quick scan suggests that the paper is reasonably well done on the transcriptional profiling side (both biological & technical replicates). But, it also points to the challenge of space research -- when is the next flight opportunity to determine how general the effect is?

I do believe there are a lot of fascinating fundamental questions to ask about biology in space. Many would be in the developmental & cellular world: to what degree does gravity influence various developmental processes. Some other research might be less about space & more about behavior: Skylab astronauts had spiders spin webs, and it took a number of trials for the spiders to learn to do it in Zero-G. It could be a fascinating way to study such behaviors & how an animal adapts to a changed environment. But, most space biology questions have an importance scaled to our commitment to manned presence in space. I'm a bit skeptical that the Salmonella experiments really help understand virulence on the ground (or more importantly, are going to be generally relevant -- but sometimes it doesn't hurt to be lucky!), but I'd sure want that line of work driven hard if I was going to spend months in space!