Does 'Y-chromosome Adam' Refute Genesis?
by Nathaniel T. Jeanson, Ph.D. *
Secular geneticists believe that modern humans can trace their male genetic ancestry back to a single man and their female genetic ancestry back to a single woman.1 Two new studies suggest that female "mitochondrial Eve" lived at roughly the same time as "Y-chromosome Adam." However, the assumptions they used to reach this dating concordance demonstrate the classic circular reasoning that besets evolutionary age calculations.
Reviewing some basics helps expose this circularity. Each person inherits two copies of the approximately 3 billion chemical letters ("A", "T", "G" and "C") of the human genome—one copy from each parent. However, offspring do not inherit perfect copies. Mutations—changes to the DNA sequence—happen every generation, making each individual genetically different from every other individual. The accumulation of these differences resembles "ticks" of a "clock," counting the time since any two people last shared a common sequence. In principle, winding back the clock should reveal the approximate date when their shared ancestor lived.
However, most of the billions of letters of DNA sequence do not act like simple clocks. Other sources of variety besides mutation can lead to differences between individuals. For example, the DNA sequence in each person is distributed among 46 chromosomes—23 are inherited from Mom, 23 from Dad. Our first parents, Adam and Eve, did not inherit their chromosomes from parents but rather received them by divine creation from God. Theoretically, God could have created Adam and Eve with DNA differences (i.e., differences from each other) from the start.
Even if Eve was a genetic clone of Adam,2 Adam may have possessed two different versions of the chromosomes that come in duplicate. Practically, this means that Adam may have had different versions of chromosomes 1-22 (i.e., 22*2 = 44, plus the X and Y for a total of 46 chromosomes). The differential distribution of these created differences among Adam and Eve's descendants, through a molecular process known as recombination, would lead to variety that is independent of mutation.3
Only two types of DNA sequences could act, hypothetically, like a simple clock. One type is Y chromosome DNA. At creation, the Y chromosome would have been present in a single copy in Adam since males have an XY chromosome pairing and females an XX pairing. Hence, differences among modern males would represent mutations to Adam's created Y chromosome sequence. More immediately, since only Noah and his biological sons boarded the Ark, all modern human Y chromosome diversity traces back to Noah's sons, who inherited their Y chromosome from Noah. Therefore, finding "Y-chromosome Adam" is, effectively, finding "Y-chromosome Noah."4
The second molecular clock candidate is mitochondrial DNA. This DNA sequence of about 16,500 DNA letters exists in addition to the 46 chromosomes, and is found in both males and females in cellular energy factories known as mitochondria. However, only females are thought to pass on their mitochondrial DNA to their offspring. Since Scripture does not specify who the wives of Shem, Ham, and Japheth were, these women may have inherited their mitochondrial DNA from separate mothers. Hence, modern mitochondrial DNA differences trace all the way back to Eve.
Exposing the evolutionary error
Calculating the date of origin for Noah and for Eve might seem straightforward. Simply count the number of Y-chromosome differences among males and the number of mitochondrial differences among all females. Then measure the rate of mutational change that is occurring today. Finally, make assumptions about the rate of change in the past to calculate when the mutational clock started ticking.
Unfortunately for the evolutionists, assumptions in past studies yielded divergent dates for the origin of modern males and females. For example, prior studies put the origin of females 100,000-200,000 years ago, but the origin of males about 50,000 years ago. Two recent studies published in the journal Science obtained the Y chromosome sequences of many more males, and these new data brought the formerly discordant results into general agreement at 120,000-200,000 years ago.5,6
This newfound agreement does not disprove the origin of Adam and Eve about 6,000 years ago, because a set of unjustified assumptions grounded their work. The "agreement" was essentially contrived to make things fit together.
For example, rather than directly measure mutation rates in various ethnicities, the authors assumed a constant rate across ethnicities. Studies published prior to the Science study in question undermine this assumption.7
Also, the authors assumed a constant rate of change through time. Scripture records a dramatic human population-altering event that happened about 4,000 years ago, and the geologic changes associated with the Flood of Noah (e.g., possible accelerated radiometric decay) may have affected the rates of DNA change.8 Furthermore, in the ~4,000 years of earth history that have elapsed since the Flood, why should we assume that the environment has been constant, doing nothing to alter the speed with which DNA mistakes occur?
Finally, the authors calibrated their molecular data to archaeological "dates." These age assignments rely on notoriously unreliable radiometric dating techniques, and, thus, are not independent validations for the molecular data.8 Rather, the "dates" reflect another set of unjustified evolutionary assumptions.
Clearly, the hundred-thousand year dates for "Y-chromosome Adam" and "mitochondrial Eve" do not bear up to careful scrutiny. All molecular-clock calculations require the observer to invoke assumptions about the past, and these Science study authors selected assumptions that fit their predetermined ideas about deep time. In the process, they relied on other disciplines saturated with evolution-friendly conjectures, and their reasoning became decidedly circular. How much better it is to start with the assumptions of Scripture, which plainly describes a recent and literal Adam and Eve, than with the ever-changing speculation of sinful man.9
- Evolutionists do not believe in a literal Adam or Eve. Rather, they claim that modern humans descended from a population of ancestors over the last several hundred thousand years. These two statements may seem at odds, but population genetics permits this seeming contradiction. The background calculations lie beyond the scope of the present article.
- "And the Lord God caused a deep sleep to fall on Adam, and he slept; and He took one of his ribs, and closed up the flesh in its place. Then the rib which the Lord God had taken from man He made into a woman, and He brought her to the man" (Genesis 2:21-22).
- See the following articles by Robert Carter for more discussion of the claims of evolutionists from these data and for a creationist response to their claims: Carter, R. Does Genetics Point to a Single Primal Couple? A response to claims to the contrary from BioLogos. Creation.com. Posted on creation.com April 30, 2011, accessed August 22, 2013. Carter, R. The Non-Mythical Adam and Eve! Refuting errors by Francis Collins and BioLogos. Creation.com. Posted on creation.com August 20, 2011; accessed August 22, 2013.
- "Now the sons of Noah who went out of the ark were Shem, Ham, and Japheth. And Ham was the father of Canaan. These three were the sons of Noah, and from these the whole earth was populated." (Genesis 9:18-19).
- Poznik, G.D. et al. 2013. Sequencing Y Chromosomes Resolves Discrepancy in Time to Common Ancestor of Males Versus Females. Science. 341 (6145): 562-565.
Francalacci, P. et al. 2013. Low-Pass DNA Sequencing of 1200 Sardinians Reconstructs European Y-Chromosome Phylogeny. Science. 341 (6145): 565-569 [http://www.sciencemag.org/content/341/6
- Conrad, D.F. et al. 2011. Variation in genome-wide mutation rates within and between human families. Nature Genetics. 43 (7): 712–714.
- Vardiman, L., A. A. Snelling and E. F. Chaffin, eds., Radioisotopes and the Age of the Earth: Results of a Young-Earth Creationist Research Initiative. El Cajon, CA: Institute for Creation Research, and Chino Valley, AZ: Creation Research Society.
- Genesis 1-2; Mark 10:6.
* Dr. Jeanson is Associate Director of Life Sciences at the Institute for Creation Research
Article posted on August 28, 2013.