In this chapter I’d like to spend a little more time discussing attempts at dating using DNA. The mutation rate of the genome is used in evolutionary theory as a “molecular clock,” a way to estimate when two species are said to have diverged from a common ancestor.
For example, if theorists want to work out roughly when humans and chimps supposedly split off from an apelike ancestor, they divide the number of DNA differences between the two species by the rate of mutations assumed to have occurred each year.
However, this method relies on several critical assumptions. The first is that the two species being compared really do share a common ancestry. In the case of humans and chimps, it is assumed that both are related by descent from some kind of apelike ancestor.
The second assumption is that we have an accurate count of the number of DNA differences between the two species being compared. In reality, researchers try to harmonize both genomes as much as possible before counting differences. Furthermore, to make the early claims of a roughly 1% difference between humans and chimps, insertions and deletions were ignored, along with dramatic differences in the Y chromosome.
Third, the molecular clock is usually calibrated to the fossil record, which is assumed to provide an independent method of dating. However, if the fossil record doesn’t reflect a gradual evolutionary change, but simply shows the sorting of materials and organic matter in a worldwide catastrophe such as the Flood, it wouldn’t be a reliable way to calibrate the molecular clock.
Fourth, the mutation rate is assumed to be broadly accurate. For a long time, scientists had used single nucleotide substitutions to calculate a rate of about one mutation in every billion base pairs for humans, implying humans became distinct about six million years ago. However, later research suggested the mutation rate was half of this, which would push the evolution of humans back at least another six million years, if we are truly related to chimps by common descent; but this would create a problem when it comes to aligning the molecular clock with the fossil record.1
The fifth assumption is that the mutation rate is regular and predictable – that is, clock-like. However, evidence indicates that it isn’t. Instead, many mutations are the result of dynamic and highly regulated stress responses, with multiple simultaneous mutations occurring within local clusters in the genome. For this reason, the authors of a review paper on mutations wrote: “Assumptions about the constant, gradual, clock-like, and environmentally blind nature of mutation are ready for retirement.” 2
Whatever the case, the so-called “molecular clock” in the genome can’t be used to prove human origins without circular reasoning. In the case of humans and chimps, it assumes the two species are related by a common ancestor, and that a slow accumulation of mutations over millions of years is responsible for the differences. But if humans and chimps were designed to be distinct from the start, then the differences between their genomes wouldn’t be the result of mutations, so using them as a kind of “clock” would produce very inaccurate dating.
However, there is another feature of eukaryotic cells that has the potential to be used as a kind of clock. As I have discussed elsewhere, most organisms have DNA in their mitochondria (known as mtDNA for short). In humans, this is just 16,569 base pairs in length. It contains genes that seem to be essential for mitochondria to function, and so the genes are preserved by natural selection. However, other parts of the mtDNA sequence don’t code for genes, and so they are potentially freer to mutate without harming the organism.
Comparing these freer parts across the animal kingdom has allowed researchers to notice something interesting. What they found is that each species has its own specific sequence, which is identical or very similar in other members of the same species; a kind of distinctive “barcode” as it were, in their mtDNA.
Based on this, the researchers concluded that most of the current living species on Earth must have arisen recently, and haven’t had time to develop a lot of diversity in their mtDNA. This means there was a genetic bottleneck in the recent past.3
For these deep time researchers, the ‘recent’ past meant within the last one to several hundred thousand years. Rather than use the mutation rate of mtDNA, the study relied on the molecular clock to make an estimation of when the bottleneck occurred – but this would make the dating unreliable, if any of the assumptions of the molecular clock are false.
The researchers weren’t proposing any catastrophic events to account for the bottleneck. However, we would expect to see a genetic bottleneck if there was a global Flood as described in the Bible. Large numbers of species would have died out, and the ones we have with us today would be the offspring of the animals on the Ark.
Now, if we were to look at mutation rates of mtDNA today, we could potentially use this to say how much mtDNA diversity should exist in a population after a specific number of years have elapsed.
For example, let’s start with a single female founder of a population and her children (since mtDNA is usually passed down from the mother to her offspring), and assume one mutation happens in mtDNA per generation. In early generations the number of mutations would be small, but as more generations come and go, more and more mutations would accumulate, and people’s mtDNA sequences would differ more widely.
If we could take DNA samples from enough people in a particular generation, we could calculate the average number of differences between the samples, and make an estimate of when the population began. Conversely, starting with a female population of one, we could make predictions about how different each DNA sample should be, if the population had been around for a specific number of years.
Using this method, and based on current mtDNA mutation rates, creationists have shown that the variation in human mtDNA is not consistent with the evolutionary paradigm, but lines up well with a founding population dating back about 6,000 years ago.4 Of course, this method also assumes that mutations are somewhat regular and consistent throughout the generations.
Whatever the case, if humans are a fairly recent creation, thousands rather than millions of years old, this would explain an apparent anomaly in the Bible. According to the creation account in the book of Genesis, Adam and Eve, the first human pair, were told to be fruitful and become many. But if they were the only humans around to begin with, their offspring would have needed to marry close relatives. Yet this was forbidden in the Law covenant given to Israel through Moses.
There is a simple genetic explanation for why marrying close relatives was outlawed at that time, as well as being a bad idea today. Close relatives could have similar or the same mutations in their genetic information. If both parents have a gene with a damaging mutation, they are much more likely to pass it on to their offspring, potentially leading to a baby with genetic defects. On the other hand, if the parents aren’t closely related, even if one parent carries a defective gene, there is a much better chance that the other parent will have a functional version of the gene, so their offspring can still inherit a working gene.
If God really did create Adam and Eve, as the Genesis account says, there would have been few if any mutations in the DNA of their immediate offspring, so marrying close relatives wouldn’t have been a problem. God only outlawed it much later, once mutations had accumulated enough to cause issues with this. The fact that the Law covenant forbade marrying a close relative reflects a good understanding of genetics.
Incidentally, if humans didn’t evolve from an apelike ancestor after all, but were created directly by YHWH, how old would Adam look at his creation? Presumably he would be a full-grown man. To our eyes, he would look at least a few decades old, yet he would have a chronological age of zero. Was God trying to fool possible observers with an appearance of age? Not at all. He simply created a functional man and woman from the start, which meant Adam’s biological age didn’t match up with his chronological age, his actual age. This same point could apply to anything God chooses to create, whether a loaf of bread, or an entire universe meant for habitation. Why would God need to make a loaf in the same way we need to make it?
While we’re on the subject, another interesting question we could ask is: why did God create Eve from a rib? This was a question that perplexed the Jewish philosopher Philo; or to be more precise, he didn’t take these details too literally, but saw them as figurative. Writing in the first century AD, he asked, “how can any one believe that a woman was made of a rib of a man, or, in short, that any human being was made out of another?” And “why, when there were so many parts of a man, did not God make the woman out of some other part rather than out of one of his ribs?” 5
He went on to give the kind of elaborate answer that theological people do when they wish to interpret a scriptural passage figuratively rather than literally. However, Philo didn’t know that there was a simple scientific answer to his question. Unlike other body parts, human ribs can grow back! 6 It’s also worth noting that bone marrow contains stem cells, which have the potential to become different types of cells found in a body.7
While I think God created Eve from one of Adam’s ribs so the first two humans weren’t independent creations, but were of the same kind, figuratively as well as literally “one flesh,” perhaps he was also using this as an object lesson to those who view the account as a parable or myth. God just happened to pick the part of Adam that could grow back naturally, and that contains stem cells, details that science has only recently discovered.
According to the Genesis account, Adam and Eve could have potentially lived forever, but they chose to become like God, knowing both good and bad. They and their offspring became separated from the source of life. Humans became subject to breakdown and death, which happens in part because of the accumulation of mutations in our cells over time.
Furthermore, as I discussed in the first part of this letter, God made a statement prior to the Flood that sounded very much like a limit to the human lifespan: “My Spirit will not reside with the human forever while he is flesh, and his days will become 120 years.” 8 I think this was done to restrain the human ability to entrench evil. The Bible records a dramatic drop in lifespans after the Flood, which would make sense if the changed environment caused damaging mutations to accumulate at a higher rate.
In any event, human lifespans have varied throughout history, depending on factors such as medical knowledge, the environment and the availability of food. However, even in more modern times, with our much better understanding of what kills us and what keeps us alive, looking at a list of the verified oldest people strongly suggests there is indeed an upper limit to the human lifespan.
At the time of writing, most of the one hundred oldest men, whose ages have been verified, died between 111 and 115 years of age, with one living to 116. For the one hundred oldest verified women, most of them died between 114 and 117 years of age, with one living to 118, and two living to 119. Jeanne Louise Calment, who died at 122 years of age, is the only person in history who has been verified to have reached the age of 120. This exception seems to highlight the rule, stated by God several thousand years ago, that without God, “his days will become 120 years.”
Fortunately, God has provided a way for each of us to reconnect with the source of life.
1 P Moorjani, Z Gao Z, M Przeworski, “Human Germline Mutation and the Erratic Evolutionary Clock”, PLOS Biology, 2016. 2 Devon M. Fitzgerald, Susan M. Rosenberg; “What is mutation? A chapter in the series: How microbes ‘jeopardize’ the modern synthesis”, PLOS Genetics, 2019. 3 Stoeckle, Thaler, “Why should mitochondria define species?”, Human Evolution, 2018. See also the article “Far from special: Humanity’s tiny DNA differences are ‘average’ in animal kingdom” published by Rockefeller University at phys.org on May 21, 2018. 4 See the article “A Young-Earth Creation Human Mitochondrial DNA ‘Clock’: Whole Mitochondrial Genome Mutation Rate Confirms D-Loop Results” by by Dr. Nathaniel T. Jeanson, published on September 23, 2015 in Answers Research Journal. 5 Philo Judaeus, Allegorical Interpretation II, Section VII. 6 See the article “Humans And Mice Can Regenerate Missing Rib” posted by Cristy Lytal at futurity.org on September 15, 2014. 7 See the letter titled “Adam’s rib and the origin of stem cells” in American Journal of Hematology, first published 11 February 2011. 8 Genesis 6:3.