>> For example, iodine (an element, not even as big as a molecule) supplementation at the fetus and early childhood stages can, among other benefits, result in as much as a 13 point IQ increase from a previously deficient region's average. This is a huge enhancement by human standards. Why hasn't evolution found a way to have our bodies produce iodine automatically (perhaps by producing iodomethane like some algae?) at that stage of life, or maybe only by the mother when the child is in the womb or perhaps produced and distributed only with breast milk? Then even if you lack natural sources of iodine you'll still benefit. It should be easy, it's just a single element!

FYI Iodine is concentrated by the breasts so as to provide it to babies via milk for exactly this reason. Iodine is critical to a lot of things. What you overlook is that as an element (atom) there is no way for the body to "make" iodine. The only way to get it is through what you eat and drink. In my opinion, the thyroid hormones are mostly a way for the body to store iodine - they are numbered T1, T2, T3, and T4 based on the number of iodine atoms in the molecule. The thyroid gland also concentrates iodine for use in making these hormones, but ultimately the only way to get iodine is to consume it - which I highly recommend.