How were the nuclei of the elements formed? We have begun to give the answer as we know it now. During the second half of the 20th century there was a long debate over this subject. Some people thought that all the 92 elements were made in the first few minutes of the universe. Others thought they were all made in the centers of the first stars. As it turned out, neither group vanquished the other. Both were partly right.
To begin with, a variety of people put forward equilibrium theories of the formation of the elements. In these theories it was generally assumed that in the early stages of the history of the universe, when all the matter was squeezed tightly together, and was presumably at very high temperature, conditions might be ripe for producing the elements by a nuclear cooking process. Such theories suffered from the difficulty that no single set of conditions of temperature and pressure would give all of the elements with the observed relative abundances, so that it was necessary to make such theories extremely complicated, with varying sets of conditions assumed to be responsible for different regions of the periodic table of the elements.[i]
[i] Truran, J. W. and A. G. W. Cameron, Chapter 23, “Nucleosynthesis,” op. cit., p. 984.
No one has found a set of conditions that could produce all the elements from pure hydrogen or from a mixture of protons and neutrons. It took two different epochs of intense pressure, heat, and light to produce all the elements. These epochs were the mornings of day one and day two.