I've listened to and enjoyed many of the Unbelievable ? debates on science and religion, most recently The Scientific Case for Adam and Eve. Could atheist biologist Nathan Lents, professor of biology at John Jay College in New York, conceivably support a hypothesis that human evolution was "propped up" by an injection of DNA from mythical biblical progenitors ? Seems unlikely, but this is the argument put forward by geneticist and christian apologist Joshua Swamidass, author of "The Genealogical Adam and Eve: The surprising science of universal ancestry".

Stephen Jay Gould in a 1997 article for Natural History magazine coined the term "non-overlapping magisteria" for the twin authorities of science and religion. If the volume and variety of articles on "theistic evolution" are indicative, modern theists largely ignore Gould's position statement, and expend their energies attempting to weave threads of biblical and supernatural narrative into established scientific theories.

I have a theory of my own. Those with deeply-held religious beliefs who are also trained in science must deal on a daily basis with the cognitive dissonance that comes with trying to adhere to two conflicting world views.  The extent to which otherwise rational scientists will go in this regard can be quite astonishing. They bring the full weight of their education, experience and intellect to bear on the problem with some surprising results.

Both Joshua Swamidass and Nathan Lents talk coherently and eloquently about the mt-MRCA and Y-MRCA but also discuss why from a genealogy point of view, we can trace our ancestors back just a few hundred years by reference to the phenomenon of pedigree collapse. However, as Joshua Swamidass would say "here's the kicker". He states confidently that "Science doesn’t actually give us a definition of ‘human’” and “You can say ‘Homo Sapien’ but there’s really no clear definition of ‘Homo Sapien’”. I think what he means is that Homo Sapiens didn't magically appear one day as a new species, but it's incorrect to say that there's no clear definition in scientific terms. Here's a clear definition: "the only member of the genus Homo that isn't extinct".

He goes on to say: “If you talk to ‘Paul’ 2,000 years ago about ‘Homo Sapiens’ that lived 100,000 years ago, he wouldn’t have known that those ‘humans’ existed”.

We begin to lift the science veneer and get our first glimpse of the dissonant hairy underbelly of Joshua's religious belief. It goes without saying that a historical figure from the 1st century CE would have no understanding of the history of human kind. We are being led toward the idea that science somehow doesn't understand "what it is to be human", but to be fair, he accepts that theology doesn't understand either. There's a good reason for this. The question "what does it mean to be human" is similar to "why are we here" and "why is there something rather than nothing". In other words, it's in the bucket of "metaphysical fundamentals" and we shouldn't waste our time trying to answer it, as there is unlikely to be a coherent answer. "It was striking how much disagreement there was among theologians on 'how to understand what human was'". Is it really all that striking, given the nebulous nature of the question.

Getting further into the debate, it becomes clear that thankfully, Nathan's Lents' aim is not to lend scientific support to Joshua's book or his dissonant examination of theistic evolution. Rather, Nathan is anxious about the perception of atheists as being somehow negative, shady and poorer for having no god to give them a moral code or a reason for living. He sees Joshua's book as an opportunity to show solidarity with those of religious faith, to demonstrate that atheists can compromise and find common ground. Whilst this is a laudable aim, I question whether assuaging one's own dissonance by embracing the theist position, rather than opposing it, will ultimately work as a strategy.

Toward the end of the debate, Joshua's coherence deteriorates. He begins to talk about "truth" in relation to human emotions and relationships, perhaps responding to a tug from the inner dissonance. At the conclusion, it felt as though these were two scientists trying to forcibly and artificially reach agreement as a show of solidarity with one another.

The most disappointing aspect of the debate was the lack of clarity around the science in Joshua's book. How do you deal with the observation that the mt-MRCA ("mt-Eve") and Y-MRCA ("Y-chromosomal-Adam"), in addition to being perpetually re-defined as maternal and paternal lines die out, would not have lived at the same time ? As we refine the definitions with new DNA evidence, surely it becomes less likely that these two would align to an actual couple. Also, what about the dates ? Estimates for (current) mt-MRCA put her at about 160,000 years ago. That's roughly 27 times older than the biblical account, depending on which estimate for the date of Genesis you believe. I'd hoped to hear some challenge to the science in the book, but sadly, none was forthcoming.

I haven't read Joshua's book but I get the clear sense that it's an attempt to bridge Gould's magisteria by trading real science (Mitochondrial DNA and human ancestry) with christian apologetics, motivated by the dissonance that comes with being a theist scientist. If the aim of the debate was to give the viewer/listener a warm fuzzy feeling seeing how science and religion really can become natural bed fellows then it didn't work for me - sorry.