What Lang pointed out is correct. Let me explain a bit more.
1. “nāmarūpa paccayā salāyatana” is a step in Paṭicca Samuppāda. That holds whenever “nāmarūpa” arises via the sequence: ““avijjā paccayā saṅkhāra; saṅkhāra paccayā viññāna; viññāna paccayā nāmarūpa.”
2. The verse, “Katamā cāvuso, jāti? Yā tesaṃ tesaṃ sattānaṃ tamhi tamhi sattanikāye jāti sañjāti okkanti abhinibbatti khandhānaṃ pātubhāvo āyatanānaṃ paṭilābho, ayaṃ vuccatāvuso: ‘jāti’.” is a general term to describe how a partcular “jāti” arises.
- As I mentioned in my first comment above, this verse is analyzed in “Jāti – Different Types of Births” starting at #4. Let me summarize by quoting from that post.
“5. For opapatika (instantaneous) births in the Deva and Brahma realms, jāti is the ONLY stage involved. A Brahma or a Deva is born instantaneously, complete with “all parts of the body.”
- It needs a bit of correction. Not only jāti but also sañjāti is involved in creating a Deva or a Brahma in an opapatika birth.
- The same two steps are also involved in the birth of a human (or animal) gandhabba at the cuti-patisandhi moment. That is an opapatika birth, too.
- Thus, all life forms are generated in the first two steps (via opapatika births).
The rest of the steps, “okkanti abhinibbatti khandhānaṃ pātubhāvo āyatanānaṃ paṭilābho” are involved in the birth of a human (or animal) with a physical body. Let us consider the process needed for a human to be born with a physical body. That is another type of jāti.
- The gandhabba must enter a matching womb (okkanti). That can take days, months, or years after the gandhabba was born at the cuti-patisandhi moment.
- The rest of the steps are in #6 of that post. I will quote them below.
(iii) When pulled into a womb, the gandhabba merges with a zygote, which is the okkanti state.
(iv) Then, that embryo grows in the womb in the abhinibbatti stage.
(v) When all body parts are formed, that is the khandhānaṃ pātubhāvo stage, and a baby then comes out of the womb. That last stage is what we commonly call a “birth.”
(vi) The sensory faculties start working as āyatana after the baby is born. This is the last āyatanānaṃ paṭilābho stage.
Now, the second point that Lang made is that the baby’s sensory faculties (indriya) cannot become āyatana until its brain is fully developed.
- I discussed this point in detail in the following (more recent) post, “Distorted Saññā Arises in Every Adult but Not in a Newborn“
- I may need to make a few more revisions to the post “Jāti – Different Types of Births” to provide more clarity by referring to the newer post “Distorted Saññā Arises in Every Adult but Not in a Newborn.“
- Let me know if there are more questions before I do that.
