Epochal trace elements and evolution.

The use of some trace elements by plants and animals during the evolutionary process has resulted in epochal changes. Noteworthy is the fact that plants (but not animals) needed boron in order to grow stems and roots as they left the seas and became anchored on land. Iodine is plentiful in sea water but rare on land. Therefore, the iodination of tyrosine provided an iodine transport mechanism which allowed for the metamorphosis and the development of warm bloodedness--a great evolutionary advantage. Zinc from clay was needed for the formation of the first primitive nucleic acids and, later, the presence of zinc in the retina provide the enhanced night vision of the nocturnal predators--a natural advantage. Hence, boron, iodine and zinc can be termed epochal trace elements. Inquiry should be directed towards the possible roles of other trace elements, which may have been epochal in evolution.