Hostility towards evolutionary biology in Christadelphian circles owes much to the perceived connection between evolution and atheism. However, it is perception that evolution destroys a historical Adam that arguably lies behind much of this antipathy. As Davis Young notes though, the problem remains acute even if evolution is rejected:
”What intrigues me, however, is that most evangelical Christians seem to be unaware that a rejection of the idea of human evolution and an insistence on a non-evolutionary creation of the human race do not thereby adequately protect biblical anthropology from possible erosion. Even on the presumption of the special creation of humanity there is other scientific evidence that has the potential for affecting our understanding of the doctrine of original sin. Arising out of Warfield's "fundamental assertion" are his two additional subsidiary questions concerning the antiquity and the unity of the human race. Although these questions were discussed vigorously in the 19th century, Warfield admitted in 1911 that "neither of them can be said to be burning questions of today." Given the explosion of extra-biblical evidence bearing on the antiquity and unity of the human race since Warfield's day, however, it is striking that these questions have received relatively little recent analysis within the evangelical community. Although anthropologists have pondered the two questions, Christian scholars in general and theologians in particular seem poorly informed about the pertinent extra-biblical evidence and its implications for Christian theology.” [77]
In short, the relevant extra-biblical evidence is the fact that fossil evidence for anatomically modern Homo sapiens extends back nearly 200,000 years [78] while there is no evidence of a sharp ‘genetic bottleneck’ dating back 6-10 thousand years as one would expect if Adam and Eve were the sole ancestors of the human race. [79-82] Needless to say, these facts are impossible to reconcile with any reading of Genesis which posits Adam and Eve as recent sole ancestors of the human race. If one reads Genesis 4 as history, this would make Cain and Abel the earliest farmers and as the earliest evidence of plant [83] and animal domestication [84] in the Ancient Near East dates back around 11000 and 10000 years ago, respectively, the earliest possible date for Adam and Eve would be no earlier than around 9000 BCE, considerably later than the date of around 195,000 BCE for the human fossils at Kibish in Ethiopia.
These facts alone make universal human descent from a recent ancestral pair extremely difficult to sustain if the first four chapters of Genesis are read as literal, historical, scientifically accurate accounts of our origins. It is the genetic evidence that makes universal human descent from two people untenable, and which has been causing no end of consternation in the evangelical Christian world [85] recently.
In essence, the problem stems from the fact that there is too much genetic diversity in the human genome to have arisen from two people living 6-10 thousand years ago. While the genetics and mathematics behind this are beyond the scope of this article, it boils down to approximating the amount of time it takes for two different forms of one gene to arise from an ancestral gene, given known mutation rates and human generation times. This approach will allow you to calculate the size of the human population during the past. What these data show is that the smallest human population size was measured in the thousands, nowhere near the literalist take on Genesis which asserts an ancestral population of two people.
A recent paper [79] in Nature analysed the genetic data from six people from Europe, East Asia and Africa, confirming what we already know from previous studies, namely that the minimum population size of the human race could not have dipped below the thousands.
Population sizes inferred from autosomes of six individuals. Source: Nature (2011) 475:493-497.
One can see that the effective population size for European and Asian genomes dipped to around 1200 between 20 to 40 thousand years ago, while the African effective population size dipped to around 5700 approximately 50 thousand years ago. Around 20,000 years ago, the human population size increased significantly. Such data effectively falsifies the hypothesis that we descend from two people living a few thousand years ago.
Even if we ignore this evidence, two other problems make the universal descent of the human race from Adam and Eve impossible. Firstly, there are many obligate human pathogens in existence, which Adam and Eve would have carried. An obligate human pathogen is one that lives exclusively on or in a human host. Examples include:
Bacteria: Chlamydia trachomatis (trachoma), Neisseria gonorrhoea (gonorrhoea), Haemophilus influenzae type B (upper and lower respiratory tract infections, meningitis, cellulitis), Bordetella pertussis (whooping cough), Mycobacterium tuberculosis (tuberculosis), Treponema pallidum (syphilis)Ectoparasites: Phthirus pubis (pubic lice), Pediculus humanus humanus (body lice), Pediculus humanus capitis (head lice)Viruses: Orthopoxvirus (smallpox)
While some obligate human pathogens have evolved recently and others are hardly lethal, the pathogens that cause tuberculosis and smallpox have been present for well over 6000 years. When they were expelled from the Garden of Eden, Adam and Eve would have been carrying a lethal load of bacteria and viruses. Any argument which posits a post-Fall creation of pathogens is merely an ad hoc reaction which has no evidence to support it, and is refuted by the fact that the genomic data obtained from these pathogens show that some of them have been around for considerably more than 6000 years. [86] It also should be pointed out that the same problem would recur in any global flood hypothesis, and would be further compounded by the fact that in close proximity to animals that would also be required to carry the pathogens that infect them, Noah and his family would quickly pick up zoonoses (infections from non-human animals) along with the obligate human pathogens they would be carrying.
Secondly, a population size of two is simply too small to withstand the crippling load of mutations that would be fixed as a result of founder effects. [87] Founder effects occur when a population is started with only a few members. In the case of any scenario where Adam and Eve were the sole members of the human race, the genetic variation would be minimal, and any de novo mutations for disorders such as Huntingdon’s disease, CADASIL (an inherited stroke disorder) or red-green colour blindness would quickly become fixed in the small population.
Given these three considerable problems, it is no longer possible to credibly defend a theory of universal recent descent from Adam and Eve. The evidence is simply overwhelming, and any attempt to posit such an idea based purely on a literal reading of selected Bible passages will brand us as obscurantists, as well as place scientifically literate believers in an intolerable position as they will be forced to “check their brains in at the door” if they want to remain members of our community and give assent to such untenable doctrines. The molecular biologist Dennis Venema, who is also an evangelical Christian and therefore cannot be accused of harbouring a militant atheist agenda points out that:
“Taken individually and collectively, population genomics studies strongly suggest that our lineage has not experienced an extreme population bottleneck in the last nine million years or more (and thus not in any hominid, nor even an australopithecine species), and that any bottlenecks our lineage did experience were a reduction only to a population of several thousand breeding individuals. As such, the hypothesis that humans are genetically derived from a single ancestral pair in the recent past has no support from a genomics perspective, and, indeed, is counter to a large body of evidence.” [88]
The recent Christianity Today cover story shows that even in the theologically conservative Evangelical community, this evidence is now becoming impossible to ignore. In response, a number of theological resolutions have been formulated [89-91] which have attracted predictably hostile responses from the fundamentalist wing of the Evangelical body. [92] Irrespective of how this latest debate plays out, the Evangelical Christian world is at least having this debate. Despite Harry Tennant’s advice in the aftermath of the Ralph Lovelock affair to honestly examine the subject of evolution and palaeoanthropology as it related to the faith, we remain in complete denial on this issue. This cannot be allowed to continue if we want our community to avoid driving away its best and brightest, and shrivel into an insular, fundamentalist vestige of its former self.
This article first appeared on my Facebook page here
References
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78. Mcdougall, Ian; Brown, FH; Fleagle, JG (2005). "Stratigraphic placement and age of modern humans from Kibish, Ethiopia". Nature 433: 733–736.
79. Li, H., R. Durbin. “Inference of human population history from individual whole-genome sequences.” Nature (2011) 475:493-497.
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87. http://evolution.berkeley.edu/evosite/evo101/IIID3Bottlenecks.shtml
88. Venema, op cit. p 175
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