When science doesn't have the answers

Oct. 1, 2000
If you've ever asked the question of how life began, you might want to take a look at the October issue of Highlights for Children

If you've ever asked the question of how life began, you might want to take a look at the October issue of Highlights for Children. There on page 24 is a fascinating article titled, "The Magnetic Sense."

In surprising detail, the writer describes how scientists are unraveling the mystery of the "sixth sense" of direction that many animals seem to possess. According to experimental evidence, creatures as diverse as birds, bees, fish, and turtles may be getting their bearings from the Earth's magnetic field using sophisticated sensory systems that function like compasses.

In one set of experiments, scientists mounted small magnets on the heads of homing pigeons to see if they could fool the birds by masking the Earth's field. Sure enough, on cloudy days, when the pigeons couldn't use the sun as a visual reference, they couldn't find their way home to save their life. Similar experiments with honeybees yielded similar results.

In their search for the sensing mechanism itself scientists got their big break from a special strain of bacteria that live in pond mud. Magnetotactic bacteria, discovered in 1975, are rod-like organisms that spend their lives oriented in a north-south direction. In a sense, they are like tiny compass needles, containing thousands of magnetic particles – known to be magnetite – that may stretch from one end of the creature to the other.

Significant formations of magnetite have subsequently been found in birds, bees, and fish, and have been confirmed (in fish at least) as the magnetic link to the brain. The next step is to figure out how the sensors work. And that's where the article ends and, as any good writer would hope, the thinking process begins.

And this is what I'm thinking: Did birds, bees, fish, and turtles always have their special magnetic sense? And as for the bacteria – what would incline them to start lugging around heavy loads of magnetite in the first place?

As I understand it, magnetobacteria expend no energy to maintain their north-south alignment. In other words, the moment of the Earth's field interacting with that of the magnetite creates a force that holds the suspended organism in the "preferred" orientation. If the bacteria are stirred up off the bottom, all they have to do is swim and since they're already pointed in the right direction they automatically end up diving back down to food and safety – without having to think about it.

Assuming there was a time when the bacteria didn't carry around magnetite, they must have been living in random orientation during the early part of their evolution. So, if natural selection was killing off the bacteria that made the tragic mistake of floating around off-axis, how could the ones that survived have given nature a chance to key in on a magnetically-based directional influence? If the organisms were aligned it wasn't because of magnetite.

But there's an even bigger dilemma. Assuming there was a natural influence causing the bacteria to pass on more and more magnetite to their offspring, at what point was the total magnetic moment substantial enough to induce sufficient force from the Earth's field to overcome the organism's own inertia? This isn't simply a matter of a little more, a little better; a lot more, a lot better.

If you analyze physics on a fine enough scale, you'll find that in order to achieve cause-and-effect you often have to overcome thresholds and activation levels that are well outside the statistical distributions of energy and matter in their various forms.

In the case of magnetobacteria, until the magnetite particles (or magnetosomes) exceed a certain volume and mass, they're just dead weight needlessly taxing the energy reserves of an organism whose every moment from birth is a struggle for life. In light of such pay-off thresholds, it's hard to imagine how natural selection would let any new function or biological system get a start.

Before you try to stone me, I do believe that natural selection is a real and active process. And I can see how it can help a species, once established, collectively tune and optimize its various systems and functions in order to survive in the face of constant change. But I just can't buy into the notion that natural selection, with or without mutation, is solely responsible for creating new and original species – and life itself – from the elements of the Earth.

My "sixth" sense tells me that the origin of life lies elsewhere, beyond the threshold of scientific proof. In that regard, it's just like “evolution” and every other theory, it has to be taken on faith.

Larry Berardinis
[email protected]

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