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Bill  Bryson - A Short History of Nearly Everything

Altogether, only about 30 of the naturally occurring elements are widespread on Earth and barely a dozen are of central importance to life ….. Oxygen is the most abundant, for example, silicon is the second most abundant, titanium is the tenth.....

Abundance has little to do with direct utility to us … there is more cerium than copper, more neodymium and lanthanum than cobalt or nitrogen …... Abundance has more to do with life itself.

Carbon for example is the 15th most common element. 

What sets the carbon atom apart is that it latches onto many other atoms including itself and forms the robust structures needed to build life – proteins and DNA....... 

Of every 200 atoms in your body 126 are hydrogen, 51 are oxygen, 19 are carbon and 3 are nitrogen. 

Other elements are critical for sustaining as opposed to creating life. 

We need iron to manufacture haemoglobin, cobalt to create vitamin B12, potassium and sodium to ensure effective nerve function; molybdenum, manganese and vanadium are used in enzyme production; zinc helps in healing – cell production; selenium is also vital in small quantities.........

Animals such as cattle have evolved to use copper.  Life has evolved to either tolerate or use small amounts of various rare elements......