By Karen Kaplan
The enamel that covers your teeth originated in an unlikely place: on the scales of ancient fish.
Scientists say they figured this out by examining the fossils of long-dead fish, as well as the DNA of a range of creatures alive today. They make their case in a report published online Wednesday by the journal Nature.
Enamel is the hardest tissue in our bodies, made almost entirely of calcium, phosphorus and other minerals. It protects our teeth when we chew and shields them from pain when encountering things that are very cold or very hot.
Nearly all four-limbed creatures have enamel, including mammals, birds, amphibians and reptiles. So do so-called lobe-finned fish, some of which evolved to walk and live on land.
Some types of primitive fish had similar kinds of tissue covering the exterior of their bodies. And some had enamel-like substances both on their exterior and on parts of their teeth. The genes needed to make all of these hard tissues are largely the same, and most are clustered together in the genome.
By comparing the teeth and outer skeletons of various groups of fish, the researchers determined that enamel first arose in fish that had skeletons made of bone. (Other fish, including sharks and rays, have skeletons made of cartilage.)
No comments:
Post a Comment