Note: This is part of a series of posts excerpted from my book, Billions of Missing Links: A Rational Look at the Mysteries Evolution Can’t Explain.
The adhesive used by barnacles is among the strongest in the world. It is reported that a layer merely 3/10,000 of an inch thick can support a weight of 7000 pounds. This relative of the shrimp and crab glues its head down and keeps its feet up to catch the next meal. Its adhesive sets in water at any temperature and will not dissolve in most acids, bases, and solvents. Fossil records suggest it has been used by barnacles unchanged for 400 million years. Nothing seems to be known about its intermediates before that.
Mussels have a similar glue, which sets underwater and has enormous strength. It takes about five minutes for the mussel to create a “dab” of this glue beneath its foot on a piling or rock. Twenty dabs will do it, and the job can be completed overnight. Imagine the consternation of intermediate species when they secreted what they thought was glue, but kept being washed away by the waves. Or the species that couldn’t store their glue and found their bivalves stuck together.