The D(esigned)-Word

“Sea urchin digging teeth are designed to stay sharp,” begins a news release from the Weizmann Institute of Science. Two of the Institute’s scientists, in conjunction with researchers elsewhere, have spent more than a decade studying how urchins dig holes into the seabed floor. The mystery is, how can urchins dig into solid limestone again and again without their five specialized teeth becoming blunt? The news release pitches the puzzling question:

The amazing part, however, is that the teeth, which need to be harder and stronger than the rocky limestone being dug out, are themselves made almost entirely of calcite—the same calcite that makes up much of the limestone. How is this possible?

The answer is a “combination of ingenious design strategies.” First, the scientists discovered crystals of strong magnesium calcite at the grinding tip of each tooth, which are in turn surrounded by a matrix of regular calcite crystals. This softer supporting structure allows the magnesium calcite crystals to remain at the surface of the tooth for maximum grinding effectiveness.

Second, the researchers used X-rays and other imaging technology to determine that the crystals are carefully aligned in two different arrays. The two arrays are interlocked right at the tip of the tooth in a way that resembles a file, augmenting the grinding capabilities of the tooth. Not only that, but the feature keeps itself sharp; wear on the tooth causes the crystals to break off in such a way that the tooth remains uneven and sharp.

We may never know exactly what God’s original purpose was in designing the urchin teeth. What is clear, however, is that the teeth are yet another marvelous design—a word the news release can’t avoid—and that this discovery adds to the ever-growing burden of complexity that evolution can only explain with time and chance.