I am new to the discussion and to your blog. The arguments above are very interesting. I have a few points to pose.
Premise 2 seems strange to me for three reasons.
1. In biology, the development of organisms is a natural function of their existence. In order to appear as a mature organism, said organism goes through a series of stages to reach maturity. Therefore, in all those stages, it is the organism that it's DNA programs it to be.
2. There are concepts of active and passive potential. A heap of scrap metal has passive potential to become a car. An agent outside the boundary of the scrap metal must do work to create a car.
A lit match and dry wood that are in physical contact have active potential to become a bonfire. In just letting the lit match and dry wood "do what they do", so to speak, the bonfire naturally matures.
The zygote, if left in the correct environment has active potential to become a fetus, baby, toddler, child, teenager, and adult. A skin cell has passive potential to become a zygote.
3. In terms of engineering, a car does not become a car because an internal stereo is added. The modified car still functions as the original car.
(In general I like the SLED test.)
Let me know what you think.