Evolution

[JALoth]

In chapter 10, you write on lines 37-42,

"Hitherto in this book, such questions were answered by invoking the forms themselves. And this can be done in this case as well. We might suppose that the form of species $A$ endows the members of $A$ with a causal power to generate new members of $A$ in some circumstances, together with new instances of the form of $A$, but also a causal power to generate new members of $B$ in other circumstances, along with new instances of the $B$ form. The difference in circumstances could be determined by the DNA content in the gametes joining together, so that when a descendant is going to have such-and-such DNA contents, the descendant gets the form of $A$, but with other DNA contents, the descendant gets the form of $B$. "

However, this only accounts for mutations over time. What about something like endosymbiotic theory? That's where one prokaryote went into another prokaryote to form a eukaryote. Would the forms of the smaller one die? There's also something called horizontal gene transfer, where genes are shared between organisms. Could a species change happen then? Would the form of the old organism go away and be replaced by a new one? (Some resources on philosophy and evolution can be found here https://www.amazon.com/dp/B08DG244TS https://www.thethirdwayofevolution.com/books and the writings of Simon Conway Morris)

You also say on lines 70-76 of chapter 10,

"But note that once we have accepted the existence of a necessary being that is the ultimate source of the varied forms in our world, we can now tweak the story to avoid the implausible idea that unicellular organisms implicitly code for the forms of elephants and unicorns. Instead of supposing that the transitions between forms corresponding to certain selected changes in genetic structure are caused by the parent forms, we can suppose that the necessary being is directly responsible for the transitions of forms. On such a view, the form of a unicellular organism might only endow its possessor with the ability to generate a descendant of the same kind, and the necessary being would directly produce any new forms when it is appropriate to do so."

This passage is confusing. Are you suggesting that God creates new species ex nihilo? That would mean evolution is false. It seems like this statement conflicts with evolution. Or are you suggesting something else? Clarification here would be helpful.

One model that I think is interesting is one where all forms are directly created by God, while the creatures create the matter. God would immediately give it its form/ensoul it. This might cohere with the Catechism's teaching that "every spiritual soul is created immediately by God - it is not 'produced' by the parents" (CCC 366). So, this could be extended to all organisms, not just humans.

[arpruss]

Thanks for the comments! I think I was suggesting something in between: God creates the form of each new species, but then within the species the form just gets passed on naturally.

[JALoth]

I see. So, for the first instance that a new species appears, the form is immediately created by God in the way that human souls are immediately created by God. Then, that species produces forms by itself. Would God mute the power of the parent organism and prevent it from creating a form in that instance? It seems like the organism is always going to create the form of itself in each reproductive cycle. So, God would be preventing that power from being exercised in the specific instance when a new species occurs. Am I getting it right?

[arpruss]

Maybe. But maybe in some or all of these cases, the prior organism's power to induce the form would itself be thwarted by the differences in offspring material structure. After all, not every reproductive output of an organism has the form of the parent--think of hydatiform moles which may just be heaps of matter.

Also, the muting could just take the shape of refraining from cooperating in the causal activity of the organism rather than any positive prevention, since I think that divine primary causal cooperation is needed to make creaturely causation effective in any case.

[JALoth]

Those are really great points and a nice clarification. Thank you!