Popular press wildly overblows “gene for humanity”

November 24, 2012 • 1:10 am

I’m about to describe one of the worst examples of science journalism I’ve seen in ages. It is a lesson on how the popular press overblows interesting scientific findings into world-shaking discoveries.

miRNAs, or “microRNAs”, are small molecules of RNA, produced by the DNA, that have recently been discovered to play an important role in gene regulation, usually by binding to a “regulatory portion” of a gene and silencing that gene (i.e., preventing its expression).

A new paper in Nature Communications by Hai Yang Hu and others (some of them from the University of Edinburgh) report a new miRNA that is specific to the human lineage: it’s not present in our closest relative, chimpanzees, or in 10 other species. By looking for miRNAs specific to humans, their clear hope was to find genes important in “humanness”: those traits that set us off from other species.

And indeed they did find one, which is what their report is about. But the popular press has distorted this finding to an unbelievable length, claiming that this is THE gene responsible for “humanity,” the one moiety of DNA that is what makes us human.

First, what did Hu et al. find? Here’s the abstract of their paper:

MicroRNA-mediated gene regulation is important in many physiological processes. Here we explore the roles of a microRNA, miR-941, in human evolution. We find that miR-941 emerged de novo in the human lineage, between six and one million years ago, from an evolutionarily volatile tandem repeat sequence. Its copy-number remains polymorphic in humans and shows a trend for decreasing copy-number with migration out of Africa. Emergence of miR-941 was accompanied by accelerated loss of miR-941-binding sites, presumably to escape regulation. We further show that miR-941 is highly expressed in pluripotent cells, repressed upon differentiation and preferentially targets genes in hedgehog- and insulin-signalling pathways, thus suggesting roles in cellular differentiation. Human-specific effects of miR-941 regulation are detectable in the brain and affect genes involved in neurotransmitter signalling. Taken together, these results implicate miR-941 in human evolution, and provide an example of rapid regulatory evolution in the human linage.

So the facts are that this miRNA, miR-941, is not found in our closest relatives, but emerged in our genome between 6 and 1 million years ago—the period of human evolution. It is highly expressed in our brain compared to other miRNAs.  Other analyses show that the early Denisovans had the gene, and modern human populations vary in copy number, with individuals having between 2 and 11 copies.  Finally, the number of potential binding sites of this regulatory molecule has decreased in humans, which the authors suspect means that some of the binding sites that remain are important in humans (but not other species’) gene regulation. There’s one more interesting observation. As the authors note:

Another hint for the potential involvement of miR-941 and its host gene in neuronal functions comes from studies of a microdeletion in chr20 q13.33 chromosomal region containing pre-miR-941. Individuals containing this microdeletion display mental retardation, developmental delay, as well as speech and language defects.

True, but as the authors note, that “microdeleted region” contains a lot more genes than just miR-941:

Besides the pre-miR-941 cluster, the deleted region usually contains more than 20 protein-coding genes. Still, it remains possible that miR-941 might be responsible for or contribute to the disease phenotype.

“Remains possible”! Indeed, but it also remains possible that deletetion of any of the other 20-odd genes, or a combination of them, could also cause the syndrome. Indeed, I suspect that since the effects of the deletion include developmental delay and speech defects, more than one gene might be responsible.  DNA sequencing of this region, and comparison to the sequences of chimps, would be most enlightening here.

The upshot: we have a human-specific molecule, miR-941, that regulates gene expression in our brains, and some of the genes it might have regulated have dropped out of the pathway. What does that mean?  We don’t really know. We don’t know what the miRNA does; only that it does something in the human brain that it doesn’t do in the brains of other mammals. And when the region containing it and many other genes is deleted, we get humans with mental retardation, developmental problems, and speech defects. The authors engage in some speculation about the importance of this gene in human evolution, but are very careful to hedge their conclusions:

In conclusion, we show that the emergence and rapid expansion of miR-941 precursor sequence took place in the human evolutionary lineage between six and one million years ago, and was accompanied by an exceptional increase in miR-941 expression level. The emergence of miR-941 was accompanied by accelerated loss of its binding sites, presumably due to deleterious effects of miR-941-guided regulation. Functionally, miR-941 could be associated with hedgehog- and insulin-signaling pathways, and thus potentially has a role in the evolution of human longevity. Furthermore, human-specific effects of miR-941 regulation are detectable in the human brain and affect genes involved in neurotransmitter signaling. Deletion of the genomic region containing pre-miR-941 results in disruption of human-specific cognitive functions including language and speech. Taken together, the unusual features of miR-941 evolution, as well as its potential association with functions linked to human longevity and cognition, suggest roles of miR-941 in the evolution of human-specific phenotypes.

Note: their results “suggest roles of miR-941 in the evolution of human-specific phenotypes.”

So what does the “popular press” do with this finding? They conclude that miR-941 is THE ONE GENE that makes us human, and differentiates us from the other apes. In a breathless piece called, erroneously, “Scientists reveal single gene is the difference between humans and apes,” (there are of course many genetic differences between humans and other apes), the website Medical Daily claims that this is the Gene For Humanity. The Medical Daily report:

Now, researchers believe that they have found the definitive difference between humans and other primates, and they think that the difference all comes down to a single gene.

Researchers from the University of Edinburgh in Scotland [JAC note: and other places, like China, which is where Hu works!] attribute the split of humanity from apes to the gene miR-941. They say that the gene played an integral role in human development and contributed to humans’ ability to use tools and learn languages.. .

Hu et al. do nothing of the sort. Read their paper (free at the link below)! Medical Daily continues with its litany of exaggeration and errors:

Humans share 96 percent of their genes with other primates. Of the 4 percent that humans alone have, a significant portion of it has been widely labeled “junk DNA”. Researchers have since [said] that “junk DNA” is functional, even though it does not code. This is the first time that a gene that humans and other primates do not share has been shown to actually have a specific function within the body.

First of all, not all “junk” DNA is functional. Larry Moran has written extensively about this on Sandwalk (e.g., here and here.) There is no basis for implying that all, or even most, junk DNA actually does something.

The claim that this is the first novel human gene that has a specific function may well be right (that conclusion is above my pay grade), since miR-941 does appear to regulate the insulin and “hedgehog” (a gene involved in development) pathway, but it may have many other functions that we don’t know.  And there are other genes that are unique to humans and not other apes; we just don’t know their function yet.  Those, too, can be “humanness” genes. I suspect, in the end, there will be dozens to hundreds of genes that explain our differences from other apes: genes involved in bipedality, loss of hair, delayed infant development, cognition, and so on. But that’s not what Medical Daily wants it readers to think: there must have been one gene:

The gene is highly active in the regions of the brain that control language learning and decision making, indicating that it may play a significant role in the higher brain functions that make humans, well, human.

It’s hard for me to believe that cognition and language all come down to the evolution of a single miRNA, and, indeed, the authors never make such a suggestion. That would imply that cognition and language arose relatively suddenly, during the period when the new miRNA arose and became “fixed” (i.e. spread to all humans).  Yet our increase in brain size took place over several million years and, I think, our mental capacity increased apace.

This is an appallingly bad example of science journalism. It’s not the fault of the authors, who are careful with their suggstions. It’s the fault of Medical Daily, which wanted to make a big splash. Shame on them. In the end, miR-941 may play a role in the difference in cognition and speech between chimps and humans. But I’d bet thousands of dollars that it doesn’t play a huge role in that difference.

This all reminds me of the gene FOXP2, once also touted as the “humanness” gene because it evolved rapidly in the human lineage and mutations in the gene affect language ability.  That gene, too, hasn’t panned out as a critical factor in the evolution of “humanness.”  We differ from our closest relatives in many, many genes, and singling out one of them as a “humanness” gene is, and will always be, a mug’s game.

Hu, H. Y. et al. 2012. Evolution of the human0-specific microRNA miR941. Nature Communications 3, Article number: 1145 doi:10.1038/ncomms2146

37 thoughts on “Popular press wildly overblows “gene for humanity”

  1. I think there are a lot of articles that sensationalize an ambiguous or nebulous research finding to cater a segment of the population who want to feel smart and have something to talk about over dinner. There must be a contingent of such journalists writing in none scholarly missives, a mixture between science and fiction. It’s nice to be reminded of that.

    1. I suppose that journalists (and especially freelance journalists) often face the choice to write in a sensationalist way, or not to write at all. Only the very best media opt for the third choice, namely giving the correct information.

      1. The sad fact is that of two articles, one giving the correct information and one the sensationalist version, 99.762% of subeditors would choose the second.

        1. The sad fact is that editors will publish whatever they think sells copy, and if that fails, will give a slant, or add a downright lie to a story, if they think it will help sell copy. They are far less interested in the veracity or accuracy of their reporting than in the size of their circulation figures. http://imgmax.com/image/4704.html

          At other times, journalists can be led, or forced, by political manipulation. http://imgmax.com/image/4705.html

  2. That’s why I come here daily to find out about stuff. I get my science news here! And Dawkins’ site, and a few other sites such as MindHacks and Science based Medicine.

  3. It’s as if all science papers need to lead, in bold, with a disclaimer section, where the authors anticipate wild speculation that might result from the paper and debunk it right off the bat. Any ‘journalist’ that then missed that could be accused of outright lying. All publishing sites would also be obliged to display the disclaimer as well as the abstract.

  4. Recently disecovered?

    Identification of novel genes coding for small expressed RNAs. Lagos-Quintana M, Rauhut R, Lendeckel W, Tuschl T. Science. 2001 Oct 26;294(5543):853-8.

    An extensive class of small RNAs in Caenorhabditis elegans. Lee RC, Ambros V.
    Science. 2001 Oct 26;294(5543):862-4.

    An abundant class of tiny RNAs with probable regulatory roles in Caenorhabditis elegans. Lau NC, Lim LP, Weinstein EG, Bartel DP. Science. 2001 Oct 26;294(5543):858-62.


    1. But even at that, the press release quotes an author as saying “. We’re now hopeful that we will find more new genes that help show what makes us human”, explicitly anticipating and rebutting the claim that this is THE ONE.

      1. LOL. You skeptics. It IS the ONE – the God Gene.

        Why would our Lord waste effort when He could infuse a soul into primitive man with one little piece of genetic material? Talk about parsimony! Our heavenly Father chose to do it with a single, masterly stroke.

        We now have definitive proof of His existence. Ergo Jesus. Ergo the bible is true. Ergo you heathens are all screwed.

        Now if you’ll excuse me, I have two more chapters of C.S. Lewis to finish before dinner.

      2. One Gene to rule them all,
        One Gene to find them,
        One Gene to bring them all
        and in the consciousness bind them.

      3. Oops, I should have updated. Lewis vs Tolkien, best of friends. Same religiousness, except Tolkien wasn’t half as boring. (No reflection on the comments of course.)

  5. How long before the Daily Mail shouts that it proves were are descended from hedgehogs?

    Great talk in Edinburgh last night, and thanks, Jerry, for the book signature. There were a couple of video cameras, so hopefully videos will be available in due course.


  6. //But I’d bet thousands of dollars that it doesn’t play a huge role in that difference.// You might want to check with Mr. Romney now that he’s got nothing else to do. He might go $10k with you on that.

  7. Could it be that this explaination for human evolution seems plausible to the public because of their limited ubderstanding of genetic change. If Mendel can illustrate change in peas as the result of a single gene then why can’t this happen with humanness? Makes perfect sense to me.

    1. The wider public is familiar with Mendelian inheritance but not its many exceptions? Polygenic traits is an example that Jerry mentions in his post.

  8. That’s a bit of a broad swipe to decry all “popular press” because of one marginal website, Jerry. There are some good science reporters (at least there used to be before a lot of them got laid off), and they serve an important role in deciphering researchers’ often opaque and poorly written papers so that the general public can learn about science. Do you want the public to get educated? Then climb off that horse. Your implicating every science reporter because of one bad example is as misguided a conclusion as that reporter’s.

    1. First, Jerry, in writing Why Evolution is True has done far more to educate the general public than anybody else ever will (unless Richard happens to pop by).

      And Jerry is well aware that there are good science reporters out there. If I recall right, he’s singled out Faye Flam (of the Philadelphia Enquirer), for example.

      But actual science reporters are few and far between in the popular press. Sure, there’re some good popular science publications, such as Science News. But that’s not the popular press.

      The popular press is what you read in supermarket newsstands and see on broadcast TV and hear on the radio.

      If any of the major broadcast news networks have reporters at Faye’s level, that’s news to me. Ditto with the national newspapers. The magazines tend to fare better, but they make up for it by being in the same pile as Popular Mechanics and O. NPR is pretty decent, but overwhelmed by Rush and Hannity and the rest of the bloviators.

      So I’d say that Jerry’s spot-on with this post.



          1. Ah, that’s a damned shame.

            What she really should be doing is a ten-minute segment at least weekly on one of the major networks. Even better if she had her own prime-time show…but, sadly, that’s a fantasy that’ll never come to pass….



    2. I think you should stop generalizing that research papers are “often opaque and poorly written.”

      At least Jerry as given examples of his generalization. You can’t even be bothered to do the same with the paper in question. Maybe you didn’t read.

  9. …”the gene FOXP2, once also touted as the “humanness” gene because it evolved rapidly in the human lineage” and expressed itself as FOXNEWS in those with mutated copies. 🙂

  10. Is it possible that a single genetic change such as the appearance of miR-941 could have changed a primate brain in such a way that it set off the rapid growth of brain size and complexity of function that characterizes the human species? I am thinking of how primate brains have been shown to enlarge in the cortical areas that control arm movement after they learn how to use a rake to get at some otherwise unreachable food.

    Is it possible that miR-941 somehow enabled some cortical areas of the brain to respond more readily to previously non-integrated cortical inputs and thus create neural networks that led to both enlarging brains and more complex neural outputs, and that the skulls of such primates were able to enlarge to house them due to either an miR-941 effect, or some other previously evolved developmental process? Or is that not a biologically plausible theory?

Leave a Reply