Thursday, November 14, 2013

Microbes are forever

I've been making the point for some time about how incredibly durable microbial life is, but perhaps this particular article makes the point better than I can myself.

The characteristics of these microbes suggest that life is not only durable, it's incredibly durable. The assumption that life arose on Earth, which is practically an obsession with some biologists, is most likely a deeply flawed one. We can see from the temperatures and pressures that bacteria survive at that many different planets other than Earth, and sometimes quite unlike it, harbor the conditions in which life could arise. Life may not be special at all; life is, more probably, a default condition, something that arises almost anywhere it can. We can assume, instead of presuming life's rarity, that life is everywhere, that it is common, and that it spreads in the same way that... well, that bacteria do.

As I've pointed out before, and as Simon Conway Morris indicates in his fine book Life's Solutions, the DNA molecule is an incredibly sophisticated piece of machinery that, to all appearances, has survived millions and probably even billions of years of evolutionary pressure to arrive in the condition that it operates in in ordinary life forms. Because it has been on the planet since the inception of life as we know it — this is nearly certain — we have to stretch the imagination past the breaking point in order to  hypothesize circumstances in which a long enough timeline existed on earth for this molecule to reach its current fine-tuned state of evolutionary sophistication. My own gut feeling, on the whole, is that life arose on another planet, and another solar system, perhaps billions upon billions of years ago, and that it may have evolved many, many times over the course of the evolution of the universe.

Because carbon has unique properties, the argument most biochemists would make is that all life forms will be carbon-based, and that almost all of them will share molecular structures quite similar to the one we see in DNA. Biochemistry, you see, is subject to tight constraints given the laws of physics and chemistry; only so many things can happen, not everything. Once you stray from the tried and true, known proven principles of known biochemistry, you have to jump through incredible hoops in order to create a condition where life employs different molecules in order to work. As Morris points out in his book, the organic chemistry of life in Betelgeuse is going to look like biochemistry on earth.

 Not only that, most of the life forms will look like the ones we have here, especially on planets similar to Earth in terms of temperature and chemical structure. What we see around us is what works; leaves look like leaves because that's what works. Fish look like fish because that's what works. Tens of thousands of Hollywood alien movies notwithstanding, alien life is going to look pretty much like life looks here. That's because evolution continually produces the same solutions to problems within the same narrow range of chemistry and physics. If life evolves again somewhere else, its chemical structure will probably look like ours; and the physical organisms it produces will probably look like us as well.

Above all, what we need to do is cultivate a respect for the durability of these organisms around us, which we seem more interested, generally speaking, in exterminating than finding ways to live with. Our habit of attempting to exterminate bacteria instead of understanding them has led to a deepening set of problems that are going to be difficult to untangle; and we will address that in future posts.

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