This is an interesting aspect that we can glean more insight into with the current scientific knowledge about star formation. Also, at the time of the Buddha, Abhidhamma was not taught to the general public, so the details about the manomaya kaya with hadaya vatthu/pasada rupa were not taught.
1. The “first humans” on the newly-formed Earth did not have dense physical bodies like ours, as discussed in “Aggañña Sutta Discussion – Introduction” and “Buddhism and Evolution – Aggañña Sutta (DN 27).” They only had the manomaya kaya, just like the Brahmas in the pabhassara Braham realm. They could see without eyes (they did not have eyes or a brain). Let us look at markers 10.5 and 10.6 ( “Aggañña Sutta (DN 27).”), which describe the first batch of humans born on Earth upon leaving the pabhassara Braham realm. @marker 10.6: “Tedha honti manomayā pītibhakkhā sayaṁpabhā antalikkhacarā subhaṭṭhāyino ciraṁ dīghamaddhānaṁ tiṭṭhanti.” OR “They have mind-made bodies, feeding on rapture, self-luminous, traveling in the air, and they remain like that for a very long time.” Thus, even though “sayaṁpabhā” literally means “self-illuminating,” in this context, it means they did not need sunlight to see. Human gandhabbas, as well as Brahmas, can see without light.
2. The other aspect is the formation process of a star. It happens gradually over millions of years. The star does not “ignite” until its mass reaches a critical density. You can search for “star formation” to find more information. Thus, in the early Earth, our Sun had not yet become a star; it was a giant gas cloud, and due to gravity, it started collapsing into a smaller size gradually. Eventually, it reaches a critical density needed for nuclear fusion and becomes a star.
- By the time the Sun ignited, the humans had developed denser bodies with eyes, brains, etc.
- Please ask questions if anything in the above is not clear.
