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The Sciences

Evolution: it works, bixbites

Bad AstronomyBy Phil PlaitNovember 14, 2008 4:00 AM

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Sometimes, a news item comes out that makes me slap my forehead and say, why didn't I think of that! In this case, it's about evolution... kinda. Scientists at the Carnegie Institution of Washington's Geophysical Laboratory have studied the different processes that change the types of minerals present on Earth over time. What they found is that, overwhelmingly, the biggest process that has changed the mineral abundances over time is... life! Yeah, us. But it makes such obvious sense. Life takes in various substances, processes them, and then, um, excretes out a different substance. And it's not just us lumbering apes eating, drinking, and pooping. Plants do it, birds do it, bees do it. Bacteria really dominate the planet, and are responsible for all sorts of chemical changes to the minerals on Earth. Life isn't the only thing going on, of course. In the beginning (if I may use that phrase), the Universe was pretty simple. A few minutes after the Big Bang the entire chemical composition of normal matter consisted of hydrogen, helium, and a taste of lithium. It wasn't for a few hundred million more years that stars formed, and started crunching these elements in their cores, converting them through nuclear fusion into carbon, nitrogen, oxygen, and more. When these stars went supernova a short time later, the explosive forces crafted the elements into even heavier ones, like iron, calcium, nickel, and so on. Eventually, simple minerals formed. These coalesced in gas clouds into more stars, orbited by planets. That's when other forces got to work: chemical changes, weathering, various pressures and temperatures transmogrifying one mineral into another. But when life formed, that's when things got serious. It changed our entire planetary atmosphere, creating free oxygen, a highly active chemical. It changed the oceans, the land. Everything. This new study confirms this idea (you can see scientist Robert Hazen talking about all this here). They found that the mineral composition of Earth has changed along with life; as life changed, so did the chemical content of our planet. And, of course, as the mineral content of the Earth changed, so did life. And almost no place has been untouched; incredibly, they found that two-thirds of the 4000 known minerals on Earth can be linked to biological activity. Like I said, this seems so obvious, but this study makes it very clear and quantifies it. It makes a strong connection between two different fields of science, which is always cool. It means we have a new way of looking at things, a new way of thinking about things, a new way to study things. And it shows one of the overwhelming strengths of science: it shows that science is not a pile of facts. It's a growing, almost living series of ideas, and that it's self-consistent. One field of science is connected to every other field, and they all hang together. In a very real sense, science is a tapestry, a woven and interconnected series of ideas... just like the Universe itself is. And that's no surprise to me at all. Science is the Universe; it's our way of investigating it, observing it, and understanding it. Science is a way to get ever closer to truth. And it works.

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