Well, thinking about it a bit more, I realized I was wildly speculating and just trying to hunt for a convoluted way to explain a soul-theory in biological terms. One insight I had which I think was useful, though, is that conventionally the definition of a "person" can be reduced from "a mind and a body" to the information (genetic or otherwise) which is the basis for that mind and body.
But anyway, there's some interesting stuff I've heard in biology which I think is relevant and may at least inspire a skeptic to consider the possibility of rebirth.
#1. Germ cell immortality.
They're the basis for sperm and egg cells, and they're pretty strange. First of all, they're considered "immortal," because they're the biological bridge between generations. To explain what this means: If you create a culture of non-germ cells, the cells have a limit to how much they can reproduce, so they have a finite lifespan, whereas germ cells can divide forever and form the basis for the entire gene pool... In the body, germ cells differentiate as either sperm or egg, and when combined with one another during fertilization, they form embryonic stem cells, which can then differentiate into any cell in the human body -- blood cells, skin cells, brain cells, etc..
So what really constitutes the conventional "you" is the information contained within this line of germ cells, whereas the other cells -- what makes up most of your body, your skins, bone, flesh, etc. -- is simply a result of reactions going on among germ cells.
In Clark's view, biology considers our germ cells our true selves. "The only purpose of somatic cells, from nature's point of view, is to optimize the survival and function of the true guardians of the DNA, the germ cells," he writes. Gametes beget gametes, and the fundamental biological beneficiary is DNA. With each generation, that DNA should encode creatures more and more adapted to their environment. It becomes quite a hallowed molecule: DNA, the essence that transcends generations, whose integrity and transmission nature has exquisitely ensured.
#2. The role of viruses in human evolution and pregnancy.
There was a documentary on this a while ago -- I forget what channel -- but it might be that viruses were the origin of life and the catalyst for further evolution...
The idea is that the structure of viruses may have helped form the structure of the first eukaryotic cell and may influence the way in which genes are expressed during pregnancy by infecting germ cells. Viruses implant their DNA in the organism they infect. Well, because viruses are the most common biological "agent" (since they're not considered alive), our entire bodies are filled with, covered with, and surrounded by viruses. Most of these viruses are benign, though. Still, instead of germ cells, could the virus be a closer example of a material component for gandhabba?
#3. Evolution's Emergence from Cosmic Interactions
Emergence is the tendency for a more complex property to emerge from a series of relatively simple interactions. So, a primordial goo on Earth billions of years ago eventually created us and our consciousness... Many biologists recognize a special kind of emergence called "strong emergence," in which an entirely new property emerges from a system which did not exhibit that property before. This is almost magical, because you could say it's as if the system is creating new properties, that the system itself is exerting an influence on its future development. So, there isn't really a strong distinction between life and lifeless. Pre-biological reactions (chemical reactions, movements in space) may eventually be seen as a superorganism, governed by a subtle form of consciousness.