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Chances are you have heard the rumor that science has pretty much obsolesced the Judeo-Christian creation narrative, particularly when it comes to Adam and Eve. So pervasive is this rumor, in fact, that Christians and Jews themselves are beginning to dismiss the Edenic pair as either an allegory or a myth. But is the rumor true? Do we know for certain that the human race did not arise from a single set of parents? Turns out it's a complicated question and one that is hotly debated among scientists, especially in the area of genetics, where the battle over human origins seems to be centered these days. Fortunately for us, Dr. Ann Gauger, a senior research scientist in molecular genetics at the Biologic Institute, whose discussion of this very topic was recently published in the book Science and Human Origins (Discovery Institute Press, 2012), has agreed to explain to us what the actual science really reveals about the possibility of an original first couple.
Why did you even bother to look into the question of Adam and Eve?
It was not my idea. A theologian friend brought me the question. He had been dialoguing on various websites and discovered that there were many people out there who were using genetic analysis to argue that there couldn't have been a single first set of parents of the human race. I had never actually considered the question before, because the prior question for me is whether the Darwinian evolution story is true. If Darwinism isn't true, then we don't have to worry about the question of Adam and Eve. Even so, I decided to look into the matter because Christians themselves were starting to contend that the scientific evidence demands that we revise Christian theology. As you'll soon see, I think this is a very poor position to take. Such arguments are way, way, way premature.
What is the scientific evidence against an original couple?
There are two or three different ways that scientists come at this question, but the very strongest case they have involves the new onslaught of information on our genome that we have acquired from DNA sequencing. We now have full human genome sequences for numerous individuals, and we also have partial genome sequences for primates such as chimpanzees and macaques. Scientists can look at this sequence data and see how much variation there is in our genome and whether or not we can account for the amount of variation that we see. If we trace a variation back over time, we can estimate how long it took for that variation to accumulate. There are a few genes where the variation is extreme, and it is these genes that some scientists present as proof that we could not have come from an original couple.
There is a particular set of genes in our DNA, called the MHC complex, that is highly, highly variant. In fact, one of the genes in this complex has over 600 variants, perhaps even as many as a thousand. An evolutionary biologist named Dr. Francisco Ayala, partly in response to the story that came out in the late eighties saying that we all descended from a single woman in Africa called "Mitochondrial Eve," deliberately set out to prove that an original couple was impossible because of this highly variable gene, which is called HLA-DRB1. Dr. Ayala sequenced the portion of the gene where all of this variation resides and then compared it to the same sequenced region in chimpanzees and macaques. Based on how the DNA compared, he drew ancestral trees, estimating back five to seven million years, when the trees ostensibly converged into a single version of the gene. What he found was that, at the time of our supposed split from chimps, there were 32 different variants in this gene, which is far too many for us to have come from a single couple. In fact, to preserve 32 different lineages, you would need a starting population of around 100,000.
What is wrong with this evidence?
Trying to reconstruct history from a string of DNA sequence is not easy and depends on a number of assumptions. First, you have to assume that the mutations occurring in the DNA happen at a steady rate and that they are random. Second, you have to assume that the mutations are not under selection, meaning they are neither good nor bad for the organism that carries them. And third, you have to assume that recombination (the rearrangement of genetic material) is happening in a uniform fashion without any signs of favoritism. If one or more of these assumptions prove false, then the findings are not reliable. Dr. Ayala's chosen piece of DNA violates all three of these assumptions.
In what ways?
A few years after Ayala published his study, another group of researchers, T. F. Bergstrom et al., found that he had chosen a piece of DNA that was actually under strong selection for variation, which violates the first assumption. Not only that, but it was subject to high rates of mutation, violating the second assumption. Finally, this piece of DNA that Ayala had chosen turned out to be susceptible to high rates of gene conversion, which of course violates the third assumption. These researchers then applied Ayala's methodology to a piece of DNA right next to the piece that he himself had selected—one that was not under strong selection—and found that there are actually only four lineages that predate five million years. Now four lineages are definitely within the reach of two first parents. They don't prove that Adam and Eve existed, but they definitely leave open that possibility. In other words, genetic sequencing has not yet verified anything about an original couple.
Does such research throw common descent into question as well?
Ah, this is interesting! When looking into the question of Adam and Eve, I found another paper that examined chimp, human, and macaque DNA in the entire MHC complex. These researchers compared the little, highly variable piece of DNA that Ayala studied with all of the DNA on either side of it—what are called introns. As one would expect, when looking at most of the MHC complex in each of these species and then comparing the resultant ancestral trees, these scientists found that all of the chimp introns matched up closest to each other, all of the macaque introns matched up closest to each other, and all of the human introns matched up closest to each other. When doing the same to the little 200-base bit that Ayala studied, however, they found that the introns were scrambled. You have chimps with humans, and humans with macaques, and macaques with chimps. Now, if common descent is true, we last shared a common ancestor with macaques 25 to 30 million years ago. But this little piece of DNA would seem to indicate that we still have a similarity to macaques, which is impossible over that length of time. In short, it does not comport with the theory of common descent.
Why is this piece of DNA different from the rest of the MHC complex?
We don't know for sure, but I can speculate. If we did, in fact, come from just two original parents, then the first thing that humans would need to do is generate a lot of diversity in this set of genes so that we could protect our population from disease. Well, it turns out that this particular gene with the strange 200-base bit might serve as the mechanism that quickly generates the diversity needed for population survival. It's right there in the literature! Anytime a population has crashed and been reduced to just a few individuals, something ended up happening that caused new variants to pop up at a much faster rate than expected. When a study was done on a neighboring gene in the MHC complex—not the one we've been talking about, but another one very close by—it was discovered that the mutation rate there was indeed much, much higher than in the rest of the DNA. This is extraordinary, and perhaps someday I will get a chance to perform the same test on the 200-base piece in question. I think that what we will find is a designed system for generating diversity to protect against population bottlenecks, which would be totally consistent with the idea of an original couple.
Do you think we will ever be able to know the truth about our origins?
I would say that unless somebody figures out how to go back in time, we will never be able to establish for certain that we arose from an evolutionary process. Now, I think we might be able to establish that we absolutely did not arise by an evolutionary process. That's a pretty strong statement, I know, but it's easier to demonstrate that we can't get from A to B than to say, "Well, it looks like we could, but we just can't prove it yet." I actually believe that we will someday falsify Darwinism, which will be great because then the question arises, "If it didn't happen by a gradual process, how did it happen?"
Is there another naturalistic explanation waiting in the wings to replace Darwinism?
There will always be people who will continue to posit naturalistic explanations because there will always be people who don't want to consider the alternative. However, I think that the more we learn about the complexity of life, and the genome in particular, the less likely it becomes that the problem of origins will be solved by naturalistic means. Things in biology are just getting more and more intensely profound and complicated, not less so. It used to be said that only two to three percent of our genome coded for protein, and the rest was junk, speaking loosely. Well, the ENCODE project is revealing that this is a complete falsehood. When I first started studying biology, a gene was a single stretch of DNA. Now we know that genes can be embedded within genes, that genes can overlap genes, and that genes are actually comprised of bits of DNA from several different chromosomes. We also know that not every protein that exists in cells is actually encoded. Rather, there's RNA editing going on that puts new information into a gene before it's ever copied into a protein. Where does that information come from? It's mind-boggling. There's nothing else in the universe like life.
What has been the reaction to your published statements on Adam and Eve?
The only substantive response I received was from a graduate student from New Zealand, and all he said was that I only critique one line of argument from 1995 and do not address the current literature. My response was that the current literature exhibits the exact same problem as that found in Ayala's research, which is that the assumptions underlying population genetics are such that we cannot guarantee that they match reality. Just because you get a model that looks like it fits the data doesn't mean that it actually represents what really happened. As I say in the book Science and Human Origins, Adam and Eve have simply not been disproven by science yet, and those who claim otherwise are misrepresenting the scientific evidence. •
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