Genealogy, Genetics, and the Power of Words
A Review of The Genealogical Adam & Eve: The Surprising Science of Universal Ancestry.
Editorial Note on the Series: In recent years, Christian scholars have been actively discussing whether a “historical Adam” can fit with evolutionary science (for a sample of the diversity of positions, see this 2014 “scorecard” and BioLogos resources on Adam and Eve). While some say no, others say yes, proposing a variety of scenarios that view Adam and Eve as real historical people and accept the scientific evidence for human evolution. However, in the discussion, some have made premature claims (including some articles at BioLogos, recently updated) that evolutionary science and population genetics rule out scenarios with a recent universal human ancestor or with a de novo created ancestral pair.
Computational biologist Joshua Swamidass’s recent book, The Genealogical Adam and Eve: The Surprising Science of Universal Ancestry, challenges these premature claims. Swamidass argues that when we think about ancestry genealogically rather than genetically, it is possible that all humans existing by the time of Jesus are descended from a pair existing only a few thousand years before. He also makes the case that this couple could have been created de novo and have descendants interbreeding with the surrounding population. Swamidass argues that this new approach allows us to retain many elements of the “traditional Christian view” concerning Adam.
BioLogos has invited three leading scholars to engage these arguments: a biologist, an Old Testament scholar, and a theologian, all working at the intersection of science and Christian theology. We hope their reviews will equip readers to engage the ongoing conversation about Adam and Eve.
Michael J. Murray
Philosopher and Senior Visiting Scholar, Franklin and Marshall College
President of BioLogos
I am grateful for this opportunity to engage with this new book by computational biologist S. Joshua Swamidass of Washington University in St. Louis. The ideas in The Genealogical Adam & Eve (GAE) have their genesis several years ago, and represent a fuller exposition of material on the Henry Center’s Sapientia web site, a PSCF article, and a post on Swamidass’s Peaceful Science web site.
GAE adds new, provocative ideas to consider that are consistent with the science we know and a range of faithful approaches to the biblical text.
As Christians and professional biologists at major public research universities, Josh Swamidass and I are motivated by many of the same concerns. We have seen far too many Christians who feel that they must make a false choice between science and their faith, and we want to help our secular colleagues to see that Christian faith is no impediment to taking science seriously.[i] Unlike Swamidass my own upbringing was not marked by a sense of conflict between science and Christian faith[ii], whereas Swamidass comes from a Young Earth Creationist (YEC) background (p. 7). Swamidass no longer holds this view; as the Peaceful Science forum puts it, he “affirms mainstream science, including evolutionary science, the common descent of all living things (including humans), methodological naturalism (though he thinks it’s incorrectly named), and an old earth.”
A key motivation for Swamidass in GAE is removing scientific show-stoppers for “traditional” Christians. The claim that recent, special creation of Adam & Eve (A&E) as ancestors of everyone alive today is incompatible with modern science is certainly one of these. In contrast, Swamidass makes this case (p. 7, 10):
“Whatever one believes about Adam and Eve, evolutionary science does not require us to reject the Genesis narrative. Adam and Eve, ancestors of us all, could have lived as recently as six thousand years ago in the Middle East…it is possible that Adam was created out of dust, and Eve out of his rib, less than ten thousand years ago. Leaving the Garden, their offspring would have blended with those outside it, biologically identical neighbors from the surrounding area. In a few thousand years, they would become genealogical ancestors of everyone.”
Swamidass may or may not hold this view; he does not say. GAE is more interested in establishing a paradigm involving genealogical science, which is capable of being folded into numerous views. Although the recent de novo creation of A&E received the most attention, genealogical ancestry is a fairly flexible paradigm, and does not depend on a particular mode of creation or calling of A&E; it could enhance several extant models for an historical A&E at various points in the timeline in ways that are consistent with what we know from biology.
Swamidass makes two “corrections” about universal ancestry via A&E (p. 12): “1. Genealogical ancestry is not genetic ancestry… 2. Human is a multivalent term, with many definitions.” For me the most penetrating insight in this book, (see especially Ch. 3), is that we moderns tend to think in terms of genetics. For Swamidass, “genetics” refers to the passage of bits of replicated genetic material (DNA), from parents to offspring.[iii] Swamidass asks us to imagine labeling bits of DNA with a colored dye. As the DNA from the gametes of one parent unite with the DNA from gametes from another parent, the total contribution of DNA from the parent with the “labeled” DNA is diminished by half and continues in each successive generation in a process another geneticist has called “homeopathic dilution”. Add to this the phenomenon of crossing over – which limits how chunks of DNA along chromosomes are inherited, and the total contribution for most of our ancestors becomes absolutely zero and does so fairly quickly.
Some Christians who focus on popular headlines could draw the incorrect inference from this that “genetics” tells us nothing useful about human origins. This would be a major mistake. People alive today carry in their genomes an evolved history, something Swamidass affirms[iv]. Christian biologists will need to continue to help the church to grasp this impressive evidence[v].
The other point of this “correction” is that the OT cannot be talking about modern genetics.[vi] The Bible’s focus is on genealogy, the connection by lineal descent of parents to their progeny.[vii] This is an important reminder for biblical studies, but Swamidass invites us to consider how genealogies work scientifically. GAE does a good job of laying out how genealogies work, based on work dating back to 1999 by Joseph Chang and colleagues[viii] and subsequently noticed by writers such as Richard Dawkins.[ix] Genealogical science is an interesting affair. The basic counterintuitive point about genealogies is easy to grasp. Each of us has two parents, each of our two parents had two parents (our grandparents), and so forth. As one goes back in time from the present just a few generations, due to this generational doubling the number of theoretical ancestors increases rapidly, so that in a small number of generations our theoretical ancestors vastly exceeds the number of people who have ever lived. This paradox is resolved, however, once we recognize that we share many ancestors in common. The mathematics of genealogical ancestry led Rohde et al (2004)[x] to the conclusion that the Most Recent Universal Genealogical Ancestors (MRUGAs) of people alive today lived as recently as 5000 years ago. There is nothing particularly unique biologically about universal genealogical ancestors (UGAs); there are many UGAs of people alive today. Importantly, few genealogical ancestors leave a genetic trace. This means that in the absence of a TARDIS or other time machine to go back and observe events, there is no obvious way to establish genealogical relatedness in the present biologically.
In their paper, Rohde et al admit there is one major uncertainty in their modeling: the effect of strong geographical isolation. They mention Tasmania, which may have been completely impassable from the Australian mainland starting about 14,000 years ago until fairly recently. If the isolation was complete, this pushes MRUGAs to a time prior to the impossibility of travel to Tasmania. Even so MRUGAs would still be remarkably recent.
GAE is unique in that it is the first[xi] thorough application of these genealogical studies to the question of Adam and Eve. The central possibility Swamidass suggests is that a specially created, biologically compatible pair of individuals in the recent past (circa 4,000 BC) would not be detectable today, yet might have been UGAs of everyone at the time of the writing of the New Testament. Swamidass sets this time frame because it comports (a) with how many conservative Christians read their Bibles, and (b) with how many interpret Paul in Acts 17:26.
How then does the apparent evidence from paleoanthropology, human genomes of today and the genomes of hominins from the past square with a recent, de novo creation of a special pair? Much hinges on people “outside the Garden” (p. 10; henceforth POTG), GAE’s shorthand for a group of individuals carrying an evolved history in their genomes capable of interbreeding with A&E’s descendants. This solves the perennial problem of where Cain got his wife (Gen. 4) and other issues, but also means that the data from genetics stands.[xii] That a recent A&E would have existed alongside other people is a common assumption by those favoring a recent representative model of A&E (see, for example, Denis Alexander’s excellent treatment[xiii]), and Swamidass delves into the complex historical notions of so-called “pre-Adamite” peoples in GAE[xiv]. I was very interested in Swamidass’s description of Young Earth Creationists who appear to be open to the notion of biologically compatible beings “outside the garden”.
An entailment of GAE is substantial biological compatibility of the progeny of a de novo created pair with POTG. How similar they would need to be at a genomic level is unclear; the similarity might need to be deep (p. 80). But if there were detectable genetic differences, such as in retroviral and other sequences present in the evolved genome of Homo sapiens[xv], they would not be detectable today. What we would then expect in the present is what we see: genetic evidence that Homo sapiens arose through common descent, all while preserving the possibility that A&E are genealogical UGAs who have left no detectable trace genetically.
This is a valuable clarification. Why? Because it opens up new possibilities for Christians committed to our lineal descent from an historical A&E who may have been told that science made this impossible[xvi]. Interestingly, when pointed out in precisely this way, including the notion of POTG, and given the additional assumption of the possibility of the miraculous, de novo creation of A&E, the basic biological point GAE makes seems uncontroversial to even an atheist biologist such as Jerry Coyne. He of course finds miraculous intervention to be nonsensical given his precommitments. But for some Christians, such as Darrel Falk, GAE came as a surprise. As Falk says on the GAE dust jacket:
I am one of the many scientists who have maintained that the existence of Adam and Eve as ancestors of all people on earth is incompatible with the scientific data. In this book, Joshua Swamidass effectively demonstrates that people like me, stuck in a specific genetic paradigm, were wrong… I failed to appreciate the biblical ramifications of this fact.
The Power of Words
The other “correction” in GAE is the focus of Part 3: lack of clarity surrounding the word “human” and related terms. Swamidass says that he is “recovering traditional doctrine of monogenesis and sole progenitorship, not making an overly clever redefinition.” (p. 98). However, as I have sought to inhabit his use of terminology, I believe that some misunderstandings of Swamidass’s writing arise because he uses words in slightly nonstandard ways. Confusion on what Swamidass meant by “humans”, for example, led to a response by Dennis Venema on the Sapientia web site that I wrote about in 2017. A few specific examples of this complexity of terminology are worth highlighting.
Human. Ch. 8 shows what a slippery thing it is to cleanly define “human” biologically or from fossil evidence. Swamidass instead suggests that we should recover theologically informed understandings. Unfortunately, as Swamidass says, it is unclear that theologians have a corner on the clarity market! “Ask ten scholars to explain the image of God, and more than fifteen different answers might be found” (p. 108).[xvii] How does GAE define “human”? Ch. 11 (p. 134; also see Table 14.1) defines two types of “humans”: (1) “biological humans”, defined scientifically, and (2) “textual humans”, those descended from A&E. Today, these labels refer to the same set of people (all of us), but earlier in history this would not be true. POTG are the biological humans in the past who were not textual humans. The fate of pre-textual, biological humans has troubled some. Do they possess the imago Dei? Such concerns are not new and not specific to GAE.[xviii] Swamidass understands Gen. 1:26-27 to mean that both those “outside the garden” and the Adamic lineage are image-bearers; POTG are not some sort of biologically compatible “subhuman” hominins. Given Swamidass’s passion for racial equality, he of all people would never condone such an idea.
Monophyletic. As a biologist, I was initially confused by GAE’s use of “monophyletic” (starting on the bottom of p. 80, but especially the definitions on p. 120). The standard definition of this word is something like “groups of organisms that share a common ancestor”[xix], whereas Swamidass means “the same biological type” (p. 85, 120). This non-standard use has been noticed by another reviewer recently, and addressed by Swamidass. Once one concedes how he uses this word, Swamidass does a good job explaining why science affirms the unity of humankind. This point is an important one misunderstood by some Christians. As Swamidass points out, Darwin was a strong supporter of the unity of humankind. The best science of today confirms Darwin’s view.
Monogenesis and sole progenitor. GAE’s use of “monogenesis” and “sole progenitor” is more challenging. In my experience when most non-specialists are asked to define “monogenesis”, they have in their mind’s eye a situation in which A&E are the single node by which all people arise, as opposed to one of many possible universal ancestors who are inserted into an interbreeding population. In contrast, “monogenesis” in GAE means “origin by genealogical descent from one couple” (p. 119). While there may be ways to consider a reduction of an evolved population to two breeding individuals, this is not what GAE means by “monogenesis”. Similarly, “sole progenitors” for Swamidass means “the one theologically special pair from whom everyone today is genealogically descended”, whereas to most non-specialists (and most biologists) “sole progenitors” means “the one and only couple from whom everyone is descended without predecessors”. While GAE clearly defines how it uses these terms, I wondered in this section if there were ways to use adjectival modifiers as GAE does for “human” to clarify the nuances.
Universal. Early in GAE, Swamidass says, “The genealogical hypothesis is that Adam and Eve are universal genealogical ancestors.” (p. 41, italics mine). The word “universal” seems clear here: a natural way to construe the argument in GAE is that all people alive at the time of the Apostle Paul’s ministry must be genealogically descended from A&E. As we saw, however, Tasmania and other geographically isolated pockets could make placing A&E at circa 4000 BC difficult, and may require an earlier date for A&E as recent UGAs. To Swamidass and to me this is not a major issue, since many Young Earth Creationists are comfortable with the idea of gaps in the biblical genealogies (GAE n. 10, p. 166). However, perhaps in response to the Tasmania issue, GAE later qualifies the word “universal”: “…even if a rare population is genealogically isolated, we do not face an ultimate problem. At stake here is merely the difference between total universal ancestry and nearly universal ancestry, with a few rare populations undetectably left outside Adam and Eve’s lineage…moreover, the evidence cannot tell us definitively anyway.” (p. 67) I found this confusing. “Total universal” seems to be a redundant turn of phrase, and detectability does not seem to affect whether A&E are actual universal ancestors or not. Although it is likely true that we should not seek airtight articulation between theology and science on this point, to the “traditional” believer, who might hold to a truly universal, single-node ancestry model, these qualifications could be confusing.
Elsewhere in GAE, Swamidass discusses contingent historical possibilities that would have allowed movements of small numbers of travelers below the limits of detection. Some will prefer other scenarios with fewer unverifiable assumptions, as my scientific colleagues might. They are usually seeking positive evidence for some hypothesis. For scientists, lack of positive evidence is usually a reason not to favor a hypothesis on the grounds of parsimony[xx]. However, if one’s hermeneutical and theological commitments seem to require a recent, de novo created A&E who are UGAs, then one’s demand for positive evidence may become less important and one’s tolerance for low probability events that have not been disproven increases.[xxi] Physics graduate student Daniel Ang, a moderator on the Peaceful Science forum, encapsulates this essential difference in GAE’s approach well, and I refer interested readers to his discussion.
I found GAE to be a fascinating read. It stimulated me to deeper thinking about many things biological and theological. Who else might benefit from GAE? As Swamidass recently explained in an interview, a key audience for GAE are “traditionalists”, whom he defines as people committed to a particular view of Scripture – especially Genesis 1-3 – that favors a recent, de novo creation of Adam and Eve. Many Christians who accept the evidence for humans as an evolved species, as well as non-Christians such as biologist Nathan Lents, have expressed the hope that GAE will provide greater space for acceptance of evolutionary biology among such “traditional” Christians. I pray that this will be so. There are some Christians who accept evidence for an ancient earth and other scientific data but feel compelled to reject evolutionary science because they thought an historical A&E were impossible. GAE is new option for such believers.
For others, GAE involves additional hurdles. Ann Gauger, of the Discovery Institute, a Roman Catholic who is skeptical of evolution, has said about GAE: “I count the cost as too high”. Many Young Earth Creationists operate from within a hermeneutic that includes many other elements beyond a recent de novo A&E, such as fixity of species, a recent, 144-hour creation framework, and a worldwide catastrophic Noahic flood. These starting points seem at odds with key assumptions in GAE of an evolved population with an ancient history (the POTG). Given his background and passions, Swamidass may be well equipped to help move conversations with these constituencies forward.
On p. 203 of GAE Swamidass writes, “I suppose I could have just made the scientific case and walked away…Somehow, I was seduced by the grander questions.” So he should have been, and so should we all. I look forward to future engagement of professional biblical and systematic theologians with GAE’s core ideas. The brief reflections in the Online Appendices of GAE and the reviews here by McCall and Collins are a start. A first book-length follow-up has just been released by Jon Garvey. Space precludes analysis of Swamidass’s imaginative thought experiments about aliens, Narnians, and the like, not to mention the perplexing mystery of the fate of “biological humans”, how one might affirm their solidarity in universal sinfulness with those genealogically descended from A&E, and to what extent early Homo sapiens populations lacked organized aggression (e.g., p. 170). Swamidass’s intriguing threefold notion of the spread of human sinfulness (p. 185), which adds the notion of existential indebtedness through genealogical descent, is especially thought-provoking. I view this entire section as “public brainstorming” that should be encouraged.
As Swamidass says (p. 223),”The grandness of the question unsettles simple answers.” Amen!
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