I like to look at the beginning of a live and try to see what there is to be seen. You only have to take a deep look at the children on maternity and see how different those beings are. Some newborns smile a lot, some cry a lot, some are struggling, some are accepting, some are afraid, some are confident.
And if you can observe their growth, then you can see how they develop differently, but also how many tendencies are always there. That mind-body happening is conditioned, and some latencies last for the whole existence of that being. Not just bodily characteristics, which are inherited from the parents, but also mind characteristics. Accepting that the mind precedes all phenomena, that conditioning of the mind doesn't came from the body, it has to come from the mind.
But if the mind is already born conditioned at birth, from where is that conditioning coming from? God? A mystical aleatory mind formation out of thin air?
The only satisfactory answer I got from my quest on religious books, is that of rebirth, kamma and anatta.
In my understanding the conditioned nature of the mind implies that there is a mind-continuum, on which the laws of conditioning take effect. The only meaningful explanation I know for the existence of different planes of existence (on which I believe for many reasons), and for the logic behind the birth of a being on this or that plane, is kamma and rebirth.
Those of you who don't accept kamma and rebirth, or think that their acceptance is not mandatory to be a Buddhist, have a better explanation for the different mind states, and latencies, of newborns?