A Case Study in Confusion

The DNA studies which have examined the most recent common ancestors for the human race along the Y-chromosome male line and the mitochondrial female line have drawn some fascinating responses which provide a case study in confusion. Both scientists and theologians have drawn a series of unwarranted conclusions based on a variety of assumptions that do not necessarily hold related to the question of whether or not the biblical Adam and Eve could have actually been real people.

The studies do not address the question of Adam and Eve. Instead, they are concerned with suggesting that humans first developed in a small population group. The names of Adam and Eve have since been imposed on the study in a provocative way of the sort that once sold newspapers. The studies examine current DNA samples to estimate how many generations ago the human race had a common male ancestor and a common female ancestor. The most recent common ancestor (MRCA) in the male line is determined by examining the Y-chromosome of living males to estimate how many mutations would have to have taken place to account for the differences in the current DNA of males. The most recent common ancestor (MRCA) in the female line is determined by examining the Mitochondria of living females to estimate how many mutations would have to have taken place to account for the differences in the current DNA of females.

The studies require the investigators to make several assumptions. First, they must assume how many DNA mutations take place in a generation (the change from parent to child). This rate does not appear to be fixed and could vary wildly under varying circumstances, so the estimate is a tentative figure. Second, the investigators must also estimate how long a period of time to assign to a generation. A generation is not a fixed unit of measurement like a meter or a pound. It varies from fruit flies to elephants for which we have current estimates based on limited time frames of current observation. For the Adam and Eve studies, however, it is necessary to estimate an average generation length over tens of thousands of years when we do not have enough data to make a calculation. An outside reader for a book project in which I made this observation pilloried my manuscript, saying that "everyone knows" a human generation in biology is twenty-five years. Yet, in the Adam and Eve studies, the researchers have tended to estimate a human generation at fifteen years. A generation is not a standard unit of measure.

One reason that the Adam and Eve studies raised such attention is that they suggest that the most recent common male ancestor, designated as Y-chromosome Adam, lived tens of thousands of years after the most recent common female ancestor, designated as Mitochondrial Eve. What no one seems to notice is that Y-chromosome Adam and Mitochondrial Eve are not the most recent common ancestors. Our most recent common ancestors lived thousands of years after the theoretical subjects of these studies. A DNA study cannot identify a most recent common ancestor because these studies can only deal with the father of the father of the father of the father and the mother of the mother of the mother of the mother. They cannot discover the mother of the mother of the father of the mother of the father of the father. They cannot switch between male and female subjects. They cannot study the way the human race actually reproduces.

My wife and I have a common ancestor who fought in the American Revolution, but he would not appear in her Mitochondrial lineage or my Y-chromosome lineage. In terms of length of generations, my wife stands in the fifth generation from Colonel John Earle, but I stand in the seventh generation. Such a discrepancy in 200 years illustrates the problem. We see the same problem with the ancestry of Jesus if we intend to use generations as a unit of measure for time. In Matthew's account of the genealogy of Jesus, Joseph falls ten generations after Zerubbabel (Mt. 1:13-16). Tradition tells us that Matthew records the genealogy of the House of David to Joseph. According to tradition, Luke gives us the genealogy of the lineage of David to Mary. In that genealogy, Mary stands in the twentieth generation from Zerubbabel over the same period of time (Lk. 3:23-27). A generation is not a standard unit of measure.

Though interesting, the Adam and Eve studies give no information of theological significance. They do not deal with Adam and Eve. We do not know if they lived before or after God made humans in his own image. We have no reason to suppose that they have any correlation to the first common ancestors made in the image of God. As for their living tens of thousands of years apart, no one seems to have noticed that Y-chromosome Adam had parents who would have been a recent common ancestor couple long after Mitochondrial Eve, and that Mitochondrial Eve would have had parents who were a common ancestor couple.

Attributing the DNA differences between currently living humans to the mutations that have occurred since the first humans is perfectly good science. More work must be done, however, before sound estimates can be made about how long ago our ancestors might be called human. And this brings us to another point of confusion. Under an evolutionary model, we may say that we have common ancestors who lived 40,000 years ago, 400,000 years ago and 4,000,000 years ago. What that model cannot tell us is when our ancestors became humans. Science does not yet have a definition for humanity that allows us to know when our ancestors became human. Body form does not do it. From a biblical perspective, the greater question concerns when humans came to be made in the image of God. For this matter, theologians also lack a common understanding.

This brief discussion does not allow room to explore the theological complaints raised against the Adam and Eve studies which many took to mean that humans have no common pair of ancestors, but they should be mentioned together with a suggestion of how theologians may also confuse matters. In a variety of articles, essays, and blogs, several theologians have presented the following basic arguments:

1. The denial of a historical Adam and Eve means the denial of the biblical doctrine of the fall. The problem with this complaint is that the doctrine of the fall was a creative theological innovation of Augustine around the year 400 which was not taught by Christians for the first centuries after Christ nor accepted by the Eastern Church. In the West, Baptists have held to the earlier understanding of the problem of universal sin in their doctrine of the age of accountability.

2. If the doctrine of the fall is not true, then Paul's telling of the gospel is false. This argument builds on the preceding argument by confusing Augustine's teaching about the fall with Paul's teaching about universal sin.

3. If Paul's teachings are false, then the Bible is not true and has no authority. This Enlightenment trail of logical dominoes now affirms a non-biblical basis for biblical authority. The biblical basis for biblical authority declared by God to Moses and affirmed throughout the New Testament is that the Scriptures have been fulfilled.

4. If Paul's teachings are false, then we will have to come up with a new storyline for the Bible. This complaint betrays a commitment to a particular theological tradition over the biblical text.

This brief discussion suggests that we should be slow to jump to conclusions about what scientific data has to say and the theological conclusions we draw from the data.

This article is part of our Symposium on the Historical Adam:

Harry "Hal" Lee Poe is the Charles Colson Professor of Faith and Culture at Union University in Jackson, Tennessee. He has written or contributed to a number of books and articles on the intersection of culture and the Gospel, including his 2004 publication, See No Evil: The Existence of Sin in an Age of Relativism.