Hi Ann and Joshua,
I’d like to respond to the questions you raised.
Regarding the number of mutations required: Ian Musgrave has argued that “no more than 238 fixed beneficial mutations is what separates us from the last common ancestor of chimps and humans,” although Professor Joe Felsenstein contends that this is a lower bound estimate. Let’s say up to 1,000, then. Of these, only a limited proportion will relate to the brain, and an even smaller proportion would have taken place at the time when our ancestors “crossed the Rubicon” and became rational. So we’re probably talking about a score of mutations at the outside that pushed our hominin ancestors’ bodies “over the edge” and into human territory. Joshua’s estimate of “perhaps just 10 or 20 coordinated mutations” therefore sounds about right. And yes, Ann, I believe, as you do, that these mutations would have been designed by God.
Ann, I fully agree with you that the human soul can only be infused at conception - whether in ancient human beings or modern ones. It’s interesting to note that Thomist philosopher Ed Feser shares this opinion. Consequently, I would reject any scenario (such as the one proposed by @AntoineSuarez) which involves God infusing a rational human soul into adult hominins. As I argued above, either their telos as children would have been to develop into a rational adult or to develop into a sub-rational creature. If we suppose the former, then no infusion of a rational soul would have been required, as they already had one. But if we suppose the latter, then such creatures possessed a form of life which was complete without rationality, just as the beasts do.
I’m still digesting your very interesting article. Re your proposal that adult members of Homo sapiens may have been endowed with a rational soul, I would like to draw your attention to Fr. Brian Harrison’s article, “Did the Human Body Evolve Naturally?”. Fr. Harrison convincingly argues that the kind of evolution envisioned by previous Popes (certainly by Pius XII) was special transformism, which granted that evolution from the first cell up to the level of hominids may have occurred in a purely naturalistic fashion, but which posited “a last-minute supernatural intervention at the moment of Adam’s conception” so as to give his embryonic body “the genetic constitution and physical features of a true human being,” making it “physically apt for - and hence requiring - a rational soul.” Fr. Harrison argues that this is the only kind of evolution that squares with Catholic doctrine. This is obviously at odds with your assumption that “the first human persons appeared within a large population of Homo sapiens,” so you’ll need to make a good case showing why you think Pius XII was mistaken on this point.
When you hypothesize that “a being’s intrinsic Telos is to give rise to rational beings,” are you talking about that being’s descendants? If you are (as you appear to be), then once again we have a case of extrinsic finality, as the goal does not relate to the perfection of that particular individual, but of some future individuals.
Of course, I can see why you wish to draw a distinction Homo erectus from a chimp, as the former has descendants which are rational beings, but as I noted above, the same would apply to the first living cell, so your argument would prove too much.
If, on the other hand, you are supposing that God might have taken a hominin (or hominins) living in the distant past, and then miraculously altered its genes before infusing a rational soul, then I’ll concede that this is theologically and philosophically more plausible. But on a philosophical level, it would still involve the death of an animal (once its original soul departs) and the beginning of a human person (once a rational soul is infused) occurring within a living body which remains the same biological individual throughout the process. To me, that sounds very fishy. But I suppose it’s just possible.
In any case, I am very glad that we agree on Option 1 being a viable scenario.
I must say this is very good news, Joshua. I hadn’t thought about it in terms of signal to noise ratios before. So it seems we are agreed on a possible scenario.
Having read C. S. Lewis’ Out of the Silent Planet trilogy in my teenage years (incidentally, I think they’re much better than his Narnia chronicles), I’m comfortable with the idea of alien intelligences existing in the cosmos. The Incarnation, however, had to have been a unique event - otherwise Jesus Christ would not be one person in two natures (human and divine), but one person in multiple natures (human, Martian, Alpha Centaurian, … and divine), which is a heretical position for any Christian who accepts the Council of Chalcedon as ecumenical. By the way, I do not share Pope Francis’ view that we would be morally obliged to baptize Martians, if they requested it. In Matthew 28:19-20, Christ commands us to make disciples of all nations, not all intelligent beings. Baptism is for humans alone.
I’d now like to comment on your proposal for a Catholic Genealogical Adam. Before I go on, let me commend you for making a truly valiant effort, @swamidass.
So far, so good, except that I think it makes more sense to suppose that God only did this to all embryos conceived subsequent to 400 kya. As I stated above, however, I’m willing to allow that it’s just possible that God may have scrambled the genes of adult hominins living at that time, before infusing a soul into them.
@swamidass, you argue that unfallen people in the distant past are no more of a theological problem than intelligent life on other planets, Scripturally, one could make a very plausible defense for this view, I’m sure.
However, I have to agree with @Agauger here. Pius XII’s statement in Humani Generis that “the faithful cannot embrace that opinion which maintains that either after Adam there existed on this earth true men who did not take their origin through natural generation from him as from the first parent of all” entails that even in the distant past, it would still have been true that all human beings were descended from Adam. Now, I’m prepared to be a little flexible and modify Pius’s statement to “descended from Adam and his tribe,” if necessary. Adam may have been the leader of a tribe which acquiesced in his decision. At least, on that scenario, no-one who is unrelated to Adam is ever conceived in original sin, even at the dawn of humanity. But the notion of original sin spreading to groups which are unconnected to Adam, just because they happen to live after Adam’s Fall, sounds very problematic to me. What gives him the right to speak for all of them? As far as I can tell, the proposal is that Adam is the first one to personally know God. But on grounds of fairness, I think it would be more fitting if humans living back then made Adam their spokesman, by some vote or act of consent.
I’m also uneasy with the phrase, “a new type of rational soul.” On the Catholic view, human souls are immaterial: they don’t come in types of any sort - not even male and female. The kind of soul God infuses into a male embryo at conception is exactly the same as the soul He infuses into a female one. Your proposal would also mean that 15,000 years ago, Stone Age people had a different kind of soul from those who practiced agriculture.
To be fair, I should mention that Germain Grisez (1929-2018), a Catholic theologian of unimpeachable orthodoxy who played a leading role in the drafting of Humanae Vitae in 1968 has defended a scenario similar to that proposed by @AntoineSuarez. In Volume 3, Chapter 14 of his work, The Way of the Lord Jesus (1997), he writes:
…[W]hile the biological evidence indicates that humankind emerged from a very large, widely scattered, interbreeding population, theology must assume that the spiritual capacity for free choice was given initially by a special divine intervention, which completed hominization, to a group of individuals small and cohesive enough to function socially as a single body. In this way, solidarity in sin by the whole of humankind was possible at the beginning. As additional groups were hominized, they emerged into an already-given existential situation, and so shared prior to any personal act in the moral condition of humankind. In this sense, they shared “by propagation not by imitation” (DS 1513/790), even if not all humans were lineal descendants of a single couple.
Even on Grisez’s scenario, however, the Fall would have taken place at the dawn of humanity, rather than hundreds of thousands of years later. So if you’d like to modify the second part of your proposal for a Catholic genealogical Adam, Joshua, I’d push the Fall back in time. My two cents.
Well, that’s about enough for now. I’d better get some shut-eye. Cheers.