These are of low mole % G + C. Considering the early conditions of the earth, maybe endospore-forming bacteria came first. However, I am not sure of this and I need more reasons. Kindly provide explanations/reasons for this.
To answer very directly - it is important to note that bacteria had to first develop as cellular and reproducing organisms. Then evolution could allow the development of protective chemicals and the evolution of these into new structures such as endospores. So endospores had to evolve in bacteria that already existed (non-sporeformers). One way to think of this is that our current endospore forming bacteria and our current non-spore forming bacteria are all descended from earlier simple forms of bacteria.
To answer very directly - it is important to note that bacteria had to first develop as cellular and reproducing organisms. Then evolution could allow the development of protective chemicals and the evolution of these into new structures such as endospores. So endospores had to evolve in bacteria that already existed (non-sporeformers). One way to think of this is that our current endospore forming bacteria and our current non-spore forming bacteria are all descended from earlier simple forms of bacteria.
The scientific view is to looking for genetic sequence that generate the process of endosporulation itself. Because if it's a losted gene in the history, it's also hard possible that sequences stay relatively stable and can found with high retio in genomic formulas of non spore dearest spaces, the %GC is limited qualitative parameter that can't give the truth purimidic and puric DNA arrangement