How Genes Have Harnessed Physics to Grow Living Things

The same pulling force that causes "tears" in a glass of wine also shapes embryos. It's another example of how genes exploit mechanical forces for growth and development. Sip a glass of wine, and you will notice liquid continuously weeping down the wetted side of the glass. In 1855, James Thomson, brother of Lord Kelvin, explained in the that these wine "tears" or "legs" result from the difference in surface tension between alcohol and water. "This fact affords an explanation of several very curious motions," Thomson wrote.