Here at Discovery Institute we have a great network of supporters. From scientists to scholars to students to youths to activists, my inbox is always full of inquiries and I’m always behind on answering them. But recently an ID supporter who has the most important job in the world — she’s the mom of five kids — emailed me about a Joe Rogan podcast from last December interviewing evolutionary biologist Bret Weinstein. We’ve highlighted other Weinstein interviews before, and they’re always interesting. But as I listened to this latest interview, I realized that Dr. Weinstein had a fascinating idea that ought to be heard.
Years ago I had the occasion to meet Dr. Weinstein at a conference and found him to be a thoughtful, open-minded scientist. He’s certainly not pro-ID — he endorses an evo-devo-based view of how new species arise — but he’s definitely willing to think for himself and challenge the consensus view when he thinks it’s warranted by the evidence. In fact, around 21:45 in his recent Rogan podcast he says that “initially I thought that intelligent design folks were anti-scientific” but quickly adds “I now know several of them in person and I quite like them and I quite like them scientifically. I actually think they have done an excellent job in pointing out the folly in evolutionary biology.” And indeed, Weinstein himself has courageously suffered for standing up for what he believes at the hands of intolerant academics. So Dr. Weinstein has many highly admirable qualities!
In any case, it’s a long podcast and I won’t take you through the whole thing. But I want to highlight one particular fascinating proposal that Weinstein makes during the interview: the idea that the number of copies of repetitive elements in our genome might be a common mechanism by which our DNA stores integer variables that are relevant to determining development and other biological processes.
Repetitive DNA = Variables in the Genome?
Around 11:00 in the podcast, Weinstein begins to discuss telomeres, and the well-accepted idea that the number of copies of repeats of particular sequences at the ends of chromosomes can determine the lifespan of a cell:
Telomeres are structures at the ends of the chromosomes that are not genes. They are repetitive sequences. They’re written in DNA, but it’s basically just a repeated series of letters again and again and again. And the telomere basically the number of repeats that are there dictates how many times a cell line can duplicate.
[…]
It’s actually a number stored the same way you would store a variable in a computer program.
The telomere, the length of a telomere is a count of how many times a cell line is allowed to divide over a lifetime. It’s a number.
He then extrapolates from this mechanism of storing a number through the number of copies of repeats to consider the possibility that this may be a common method of storing integers in the genome:
And what occurred to me all those years ago was that the ability to store a number in the genome is fantastically powerful. What it means — if you could store a lot of numbers in the genome — is that you could describe creatures by allotting something, either a quantity of material or an amount of time in development, that you could specify things in the language of numbers that you can’t specify in the language of amino acids.
So the hypothesis that I’m putting on the table is that the evolutionary process has built a system in which variables — in which integers — are stored in DNA, and those integers dictate phenomena like developmental timing, like the growth of one of those phalanx the phalanges in the fingers, if you could radically the number that dictated the length of one of those bones then selection would effectively be in a position to play with adjacent forms.
Now a big part of Weinstein’s point here is to propose an evo-devo model where changing the number of copies of repeats in the genome might be a mechanism of evolution. He might be on to something at some level — but let’s bracket that thought for today because I just want to appreciate what he’s saying about the operation of the genome: In short, Weinstein is proposing that the number of copies of repetitive DNA is the means by which the genome stores integer variables. This suggests a potentially powerful function for repetitive DNA.
Not the First Function Proposed for Repetitive DNA
This is hardly the first time that scientists have proposed functions for repetitive DNA. We’ve been talking lately about how ERVs (a form of repetitive DNA) play crucial roles in human embryonic development. Last year we also discussed genetic differences between humans and chimps and how they often entail repetitive DNA that is functional (see here and here) — including different numbers of copies of repetitive sequences. It also seems that much of the intraspecific genetic differences within humans entail differences in the number of copies of repetitive DNA. In fact in 2024 Richard Sternberg, Jonathan McLatchie, and I posted a list of dozens of papers finding function for repetitive DNA.
So function for repetitive DNA is nothing new — but Weinstein’s proposal that the number of copies of repeats might be the means by which our genome stores integer variables is fascinating. We’re beginning to learn that there can be a lot of differences in copy numbers of repeats both between species (e.g., between humans and apes) and also between humans within our species. Some folks want to dismiss these differences as meaningless junk. But could these differences in repeat copy numbers represent a designed mechanism of storing different integer-related variables that determine processes that make species, or individuals within species, different from one-another?
DNA Repeats “Traditionally Dismissed as Junk”
Weinstein later asks if telomeres are a “special case” due to their placement at the ends of chromosomes. He then proposes that this mechanism of storing variables in repetitive DNA might be extremely common to the point that what biologists have “traditionally dismissed as junk DNA” might be a major source of genomic and developmental information:
What there are, are a bunch of sequences that were traditionally dismissed as junk DNA that have been used as a molecular marker in biology for decades. We use something called microsatellites.
Microsatellite is a repetitive sequence in DNA that does not code for a protein (it’s just like a telomere in that way) and they vary in length — they vary in length a lot. So you might have a species in which the genome is very homogeneous but between populations there will have been change in the length of these microsatellites — changes that as far as we know don’t make any difference.
But if you’re a biologist in the field and you want to know if the trees in this valley are more closely related to the trees in valley A or valley B, you can look at a particular microsatellite and you say these trees have a microsatellite at this location that is more similar in length to population A than population B, thus with some confidence we think it evolved from population A.
So we use them as a tool for assessing things like relatedness. But we don’t typically think of them as a storage modality for a kind of information that might be useful.
…And by the way these things are extremely common in the genome. There are many more variable number tandem repeats in the genome than there are genes. And my point is I don’t know whether evolution uses them as a place to store variables that then become important in describing creatures, but evolution is a very clever process. …what I’m arguing is that there is in principle the possibility for a vast library of variables that have developmental implications for the way creatures look. [Emphasis added.]
Again, Weinstein wants to propose that changing these integer variables might be a mechanism of evolution — something that we IDers are open to considering as a designed mechanism for rapid small-scale adaptation. (For example, see this study which found that changing the number of copies of repeats of STRs can rheostatically fine-tune gene expression.) That’s a conversation for another day. For the moment, simply consider his fascinating proposal that the number of copies of repeats might be a mechanism of storing integer variables (or presumably, other types of variables) in the genome. This opens up a world of potential functions for repetitive DNA that open-minded scientists can consider — provided that repetitive DNA doesn’t continue to be, as he put it, “dismissed as junk”!