December 10, 2008

Sea Grapes, Evolution and Science

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Scientists have recently discovered one of the largest single-celled organisms in the seafloor of the Bahamas. Why should you care? Because it’s providing Gromia sphaerica, a distant relative of the amoeba. It is only one cell and yet it’s the size of a grape. It looks like a mud-covered blob or, as the researchers termed it, a “doo-doo ball.” They move by rolling about on the ocean floor.

But these “sea grapes” do something that single-celled creatures have never been known to do: They leave visible tracks. Researchers found them leaving trails as long as 20 inches in the mud.

A seemingly trivial discovery. But Dr. Mikhail Matz from the University of Texas in Austin, one of the researchers who discovered the organism, claims this will force scientists to rethink the fossil record.


Perhaps you have heard of the Cambrian Explosion, which took place around 530 million years ago. Before this time period, the fossil record indicates that life on earth consisted of simple unicellular creatures. But during this time, a large variety of multicellular organisms, including organisms with bilateral symmetry, are first noted in the fossil record. This would mean that complex life rapidly appeared over the course of 70 to 80 million years.

Scientists originally believed only bilateral organisms could leave fossilized tracks, since they could move in one direction and could leave these impressions by shifting their weight from one side to another. The problem is that there are Pre-cambrian fossil tracks, which some scientists claim is evidence that organisms with bilateral symmetry existed before the Cambrian period. They would argue that complex life evolved slowly over time instead of rapidly, which would mean that the Cambrian Explosion was nothing of the sort.


But Dr. Matz said that “sea grapes” can leave traces with a similar profile to these Pre-cambrian track fossils, suggesting that perhaps the Cambrian Explosion was indeed an explosion of complex life. An article in The New York Times quotes Dr. Matz as saying, “This is really a hard hit for the school of thought that animals slowly evolved in the Precambrian.”

Others, such as geologist Dr. Chris Rowan ( are more skeptical. Rowan said there were fossils with large body forms before the Cambrian era. Nevertheless, he said that this discovery will make scientists be more cautious when dealing with fossil tracks.

All this to say, scientists don’t always agree. I don’t know how most people think of scientists, but I don’t think they’re viewed as researchers competing against others. These articles give you a hint of that, and in some respects it’s true. Everyone wants to publish his ideas and discoveries first and, given how many researchers are out there, it is almost inevitable that someone is doing the same kind of research as you are. And even if you do publish first, a competitor may try to replicate your findings or use your evidence in order to create alternative theories that invalidate yours.

This scientific controversy also shows that scientists are often interested in challenging the norm. The Cambrian Explosion model of life is as old as the 1800s, but you see scientists interested in invalidating the model. Why? Because if they do so, they’ll have made a major breakthrough and they’ll be famous for it. That’s part of what makes science so exciting. It’s not just building ideas on top of one another. It provides room to go back and revise theories, or even propose radically new ones, provided you have the data to back it up, of course.