Glad you found the article thought-provoking and thanks for taking time to comment.

As I understand, stars end in one of two way: either collapsing into a 'white dwarf' or exploding in a 'supernova'. Iron is formed when hydrogen is exhausted near the end of a star's life and if the star is large enough to continue nuclear reactions to produce elements like carbon, oxygen, and iron. Those elements are released if it then explodes. There were many supernovae before the Earth then formed from their 'elemental dust'.

Clearly, Carl Sagan put it more eloquently than I did when he said, "...the nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff."

You got me thinking about so-called hillforts and similar fortified settlements. They probably all had animal corrals because livestock was valuable and desirable. Perhaps the corrals were fortified for that reason and the fort was the result - providing defensive structures for the people along with their stock...