Ok, here's something interesting to puzzle over. From the descriptions of the Abhidharma, a being dies and due to the force of karma, etc., goes into intermediate state where it sees its future father and mother copulating, because it is attracted to the sex organ of one of them, it becomes the opposite of that sex. Then Vasubhandu states that a cow for example will be reborn a cow not a buffalo, because it's habits, etc., cause that continuation.
Sounds perfectly reasonable, however, what about artificial insemination? There are no sex organs involved, and the species can be hybrid. The Abhidharmists, to their credit, did anticipate atoms, though they did not get it exactly right, they did get that they consist of parts and those parts consist of parts until there is nothing left. But they did not anticipate genes.
The Dalai Lama has said the Abhidharma must be revised due to new science, but he wants that new science to develop further so that it's more than just mere theory. The whole of atomic chemistry, quantum mechanics and all of it fits quite nicely with the theory of dependent origination. But genetics sort of obliterates the teachings of reincarnation. But it's not so easy to be rid of bardo, ghosts and dakinis.
If you spend any time with the Tibetans and Indians you will come to see that supernatural stuff is pretty normal. There are real masters that remember their past lives, and masters that can suspend the death process. The teachings related to phowa and bardo do work. So what is this about the bardo?
Conjectures aside, the arising of a mind from DNA manipulation is clearly possible. There's no copulation and no prior species in the continuation. Then there are situations like the polar bears mating with the grizzlies. That hasn't been done before either. Clearly, Abhidharma needs a revise in this area.
I suggest the following: We take our direction from instructions on Buddhahood.
It boils down to potentiality. When a sentient being takes up the buddhist path, then the potential for buddhaood is awakened, and the qualities are matured over time. It is the same for sentient beings, the qualities for the existence of a sentient being mature over time. For example, when the new universe takes shape, the winds stir and the elements form, and sentient beings start their progression. The potential for a sentient being is in the molecules, clearly, and when the conditions are set, the sentient being can arise.
Then, as to the bardo, it is inconclusive. The bardo is an intermediate state, plain and simple. The whole scheme of being attracted to the opposite sex organs, and all that does actually happen, but it would not be conclusive. This would not be a direct cause the birth; perhaps a contributory cause. It would simply be a very deep desire for birth. Then, the way that rebirth actually happens would have to go the route of "the maturation of karma is inconceivable," as sutra says.
Despite the problems with the tulku system, how do we explain the cases where the tulkus are found where they say they will be found in their letter from the previous life, and then they grow up to be great world leaders of Buddhism like the HHDL? In some inconceivable way, when a bodhisattva master engages the methods on bardo, he or she is able to do something karmic that can result in the birth of a great man. HHDL is not just some great master; his depth and breadth of knowledge rivals any of the great masters in history. How could a group of Tibetans have just randomly accidentally selected such a child and had that happen? Isn't that inconceivable? But that's what happened.
Masters are able to be conscious in the bardo and prevent the body from decomposing. A master can dissolve his body into nothing, leaving only hair and nails. They are arresting and redirecting the death process. The number of instances are so numerous that one has to conclude the teachings on karma and rebirth do work. Accumulating vast stores of merit by realizing emptiness does give one the power to direct rebirth. But exactly how that happens is simply inconceivable.
This just crossed my mind: The beings that are reborn in the petri dishes? Maybe they are the scientists that love and find wonder in that.