Countdown to Extinction

There are only a handful of articles left in the November 2012 edition of Acts & Facts that are worth close inspection. One of these, oddly enough, is by the prolific Brian Thomas. Most of Thomas’ Acts & Facts articles seem to be repeats of stuff that we have already covered, but his November article – Human Mutation Clock Confirms Creation – is a rare exception in that it seems to be largely new.

The idea, of course, is not. Brian’s argument is that of genetic entropy, which is the idea that a build up of genetic mutations will eventually be the end of us and also precludes the possibility of our ancestors having survived long enough to evolving into humans. As evidence he points to an August Nature paper that apparently showed a mutation rate of “an average of 63.2 new mutations” per generation. But first, Thomas takes the time to estimate the number of generations that have graced the Earth:

The most widely accepted evolutionary conjectures assert that mankind evolved from an unidentified ape-like ancestor at least 2.4 million years ago. Humans may have experienced 120,000 generations in that time. In contrast, Scripture tells us that there were about 100 generations from Adam to Christ. Considering another 100 generations since Christ, a total of about 200 generations have passed since the time of creation.

It’s worth remembering that, for extra-biblical generations, Thomas is using the figure of 20 years/generation that seems to be common among creationists making the same argument – hence, 100 generations in the last 2000 years. The 2.4 million years figure is disputable, but it’s also not particularly relevant. Meanwhile, the “100 generations from Adam to Christ” are apparently calculated with the following methodology (according to a footnote):

Average the numbers of generations listed in Mary’s genealogy from Matthew 1 plus those given in Genesis 5 with the number of generations listed in Joseph’s genealogy from Luke 3.

Many of you may already know about the problem with these two famous biblical genealogies. For those that don’t, here’s a rundown:

The first few verses of Matthew 1, the first chapter of the first book of the New Testament, are devoted to a claimed genealogy of Jesus. This runs from Abraham to Jesus, via King David, concluding:

1:16 And Jacob begat Joseph the husband of Mary, of whom was born Jesus, who is called Christ.

Fair enough (the whole ‘Jesus wasn’t actually Joseph’s son’ thing is acknowledged in a round-about way, and doesn’t change anything here). However, Luke 3 also offers a genealogy of Jesus. This goes in the opposite direction, starting with Jesus and going all the way back to Adam, via both David and Abraham as before. This begins:

3:23 And Jesus himself began to be about thirty years of age, being (as was supposed) the son of Joseph, which was the son of Heli,

As you can tell, there’s a bit of a contradiction here – is Joseph’s father Jacob or Heli? Comparing the David-Joseph portions of both lists shows that the differences are much more widespread, with very few names appearing in both. This is an obvious problem for biblical innerency, and the common solution is to claim that one genealogy of the two actually belongs to Mary. As you can see from the above verses this is biblically baseless, and requires that the Mary genealogy jumps from Joseph to his father-in-law without warning.

Having decided that one genealogy belongs to Mary, and the other to Joseph, the question is which is which. According to Brian, Matthew goes with Mary and Luke goes with Joseph. But this seems to be the wrong way around – the Matthew listing is comprised of ‘begats,’ which leave no room for the necessary shenanigans. Oops.

Of course, while that’s all very interesting it’s also, once again, irrelevant. Getting to the more important part we learn:

In what is by far the most extensive of these kinds of reports, geneticists tallied each new mutation in 219 people, including 78 parent-offspring trios of Icelandic families. They found an average of 63.2 new mutations per trio, meaning that about 60 new mutations are added to each new generation. Prior studies indicate that up to ten percent of new mutations are deleterious (harmful), most mutations cause no noticeable change, and beneficial mutations are virtually unknown.

The “up to ten percent” line may be useful elsewhere as a quote, especially given that it’s about accurate, so I’ll remember that. Thomas’ assessment is correct enough for today, though there is of course plenty still wrong with it.

The paper in question is Rate of de novo mutations and the importance of father’s age to disease risk (pdf), from Nature. While Brian’s figures seem to be correct, there is another factor at play – the age of the father. For while the mother of a child tends to provide about 15 new mutations, the amount provided by the father varies considerably. Apparently, a 40 year old father will give their child 65 mutations, but if he is 20 he will only give 25. Given that Thomas is using a 20 year generation time it is clear that he should not be talking about the average mutation rate here.

Plainly, human DNA sequence quality is relentlessly worsening. [Alexey] Kondrashov wrote [in his News and Views article], “Because deleterious mutations are much more common than beneficial ones, evolution under this relaxed selection will inevitably lead to a decline in the mean fitness of the population.” An inevitable “decline” in a population’s “fitness” is certainly not what most people ascribe to “evolution”!

It’s worth realising here that the “relaxed selection” Kondrashov is talking about is the result of our modern lifestyles, when compared to our civilisation-less ancestors. He adds, immediately following the part quoted:

Indeed, data obtained from Drosophila fruitflies in experimental situations of relaxed selection suggest that this decline can be quite rapid.

My interpretation of that is that, under certain conditions, the genetic entropy really could be a problem. But this cannot be applied to the past to show that we could not have evolved, though it could possibly be used to show that we wont last very long.

Each new DNA typo is a tick from a genetic clock counting down to zero. And everybody knows what happens to a clock that stops ticking. Eventually, mutations render vital DNA sequences illegible to cellular machinery, and nobody but the Creator can reverse this inevitable genetic decline.

Everyone loves a mixed metaphor – a clock that stops ticking is right twice a day, no?

This process sets a reasonable maximum limit to the total number of possible human generations. At 60 new mutations per generation, evolution’s 120,000 generations would produce 7,200,000 mutations among the three billion letters that comprise the human genome. This greatly exceeds the human genome mutation tolerance.

Thomas cites this to a 2008 paper in the Journal of Creation. Specifically, he says:

One study estimated human genome collapse after 32,800 years in a population of 1011 and a 1.5 percent fitness decline per generation. See Williams, A. 2008. Mutations: evolution’s engine becomes evolution’s end! Journal of Creation. 22 (2): 60-66.

Where he says “1011” he actually means “ten to the eleventh power,” or a hundred billion. Williams’ paper includes a variety of flawed, contradictory ways of calculating the amount of time it would take for humans to go extinct via genetic entropy. This particular value is in fact calculated by cumulatively multiplying a hundred billion by 98.5% every 20-year generation, until there are less than two people remaining. You can see what I mean by “flawed.”

Another, more complex system used by Williams involves assuming that the entire genome is functional and made up of a large number of discrete, functional units. A certain number of mutations are required to knock out a unit, and after a certain number of units are knocked out you can no-longer survive and breed. Of course, these assumptions are largely baseless – but they do come out with much longer periods of time than the 98.5% calculation.

I find it interesting that very few of the models used by creationists take into account the fact that, as a species, we reproduce sexually. For example, while you may inherit 60 mutations from your parents only some of them will actually be passed down to your children, and some more will come from the other parent. There is also the problem of actually fixing the mutations in the population – is it enough that we are all afflicted by different genetic disorders? And don’t forget that we have two copies of each chromosome, so while there may be a mistake on one the other is still there as a backup. These problems and more would complicate any real calculation of whether or not natural selection is sufficient to overcome the mutational load, but it appears that either Excel or the creationist themselves are incapable of comprehending the world of sex.

Thomas concludes:

In contrast, the biblical estimate of 200 generations would have produced about 12,000 non-lethal mutations by now—enough to cause increasing diseases, but not yet enough to ruin the human race. The mutational countdown is steady and relentless. The reason we have not yet reached the end must be because we began our journey recently—only thousands of years ago.

Or, because we have only recently managed to relax the selection pressures that have inadvertently saved us from doom. It’s a brave new world out there…

By the way, back about a month ago I said this:

13,407,517 – remember that number for a later article.

That figure was the number of SNPs – i.e. mutations – found by a study between some Africans and the “human genome reference sequence.” That’s a hell of a lot more than the twelve thousand Thomas thinks have had time to accumulate, no-matter how you slice it. I wonder how he explains that?

3 thoughts on “Countdown to Extinction

  1. Oddly enough arch conservative Pat Robertson has been saying that 6,000 years and 100 generations are not in the Bible but are interpretations by Bishop Ussher and thus not from God. Not that this will upset Ken Ham or ICR who will just call Robertson a compromiser.

    • I too can’t wait for the fallout from Pat Robertson’s comment. If Creationists act like I think they might, there won’t be enough popcorn in the world.

  2. Short wait, it has started:

    It has links to Ken Ham’s reactions too.

    There have all along also been anti-evolution Old-Earth Creationists (OECs) too, f’instance, Hugh Ross at…

    …but OECs are a marginalized minority among anti-evolution so-called “scientific” creationists, most of them are YECs. I am not a fan of Pat Robertson’s, but his recent public statement about the Bible and the age of Earth boosted my slim esteem for him upwards perhaps a quarter of a notch.


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