How many times have you heard it said that the human and chimpanzee genomes are so similar that they are only “1 percent different” at the level of their DNA? This shows, we were told, not only that humans and chimps share common ancestry, but that humans aren’t all that special, which is a common talking point in science journalism and other public discussions. After all, we’re just slightly modified chimps! This “fact” has been discussed so much that it has become what the late biologist Jonathan Wells famously called an “icon of evolution.” 

But now, new data reported in a recently published Nature paper by Yoo et al. has overturned this previous claim. The new findings reveal that human DNA is far more different from chimp DNA than previously thought. 

That should be major news in the science world, yet those involved don’t seem interested in highlighting their discovery. More on that later.

Many times over the years, I’ve discussed how this 1 percent claim about humans and chimps is likely wrong. It is also misleading. No matter how similar humans might be to chimps at the genetic level, anyone who has been to the zoo knows already that chimps and humans are vastly different. After all, we’re the ones writing scientific papers about them—not the other way around. So common sense alone dictates that there is something misleading about that number and how it is used.  But the new data show that the previous statistic isn’t just misleading. It’s flat-out false.

 As I will elaborate in a subsequent article, this team of researchers has published “complete” sequences of ape genomes that were created ‘from scratch’ rather than using the human genome as a template. As a result, for the first time we can attempt a much more accurate assessment of the true degree of difference between the human and chimp genomes. 

The results are groundbreaking:

• At least 12.5 percent and possibly up to 13.3 percent of the chimp and human genomes represent a “gap difference” between the two genomes. That means there’s a “gap” in one genome compared to the other, often where they are so different, they cannot even be aligned.

• There are also significant alignable sections of the two genomes that show “short nucleotide variations” which differ by only about 1.5 percent. We can add this difference to the “gap difference,” and calculate a 14 percent to 14.9 percent total difference between human and chimp genomes. This means that the actual difference between human and chimp DNA is 14 times greater than the often-quoted 1 percent statistic. 

It’s true that large portions of the human genome are still only about 1.5 percent genetically different from the chimp genome. We’ll explore what that means in a subsequent post. But the new data reveal just how little this one fact tells us about the overall picture. We now know that major portions of the two genomes — 12.5 percent to 13.3 percent of the human genome, in fact — are so different that arguably the sections are unalignable and/or not directly present in one genome or the other. 

Burying the Lede

One very peculiar thing about the research just published is that nowhere in the technical paper is this bombshell discovery clearly reported, and nowhere is it stated clearly that human and chimp DNA is some ~14 percent different. Even an explainer article in Nature — which usually do a great job of translating technical findings for the average scientist — does not mention this huge finding. You have to dig deep into the Supplementary Data to find it, and even there it is opaquely stated in technical jargon. 

This data has huge implications for the long-quoted statistic that we are only 1 percent genetically different from chimps, and many people are interested in this question for its implications regarding evolution, origins, and the exceptional status of human beings. Yet the papers almost seemed like they want to obscure the numbers, making them hard to find for the reader, whether a scientist or layman.

How hard would it have been for the original Nature paper or — even better — the explainer article to say that this new data shows that the human and chimp genomes are more like 14 percent to 15 percent different rather than 1 percent? 

And yet for some very strange reason they did not do that. In journalism, this is called “burying the lede” — putting the main point of your reporting, the most notable fact, under a heap of less important verbiage. Sometimes this happens due to incompetence. Other times, it is deliberate. 

Remembering the Icon

As Jonathan Wells taught us, “icons of evolution” are arguments for evolution that get recycled over and over again — yet are not true. How do we know the 1 percent statistic is such an icon? Science popularizer Bill Nye, “The Science Guy,” provided a great example when he wrote in his 2014 book Undeniable: 

As our understanding of DNA has increased, we have come to understand that we share around 98.8 percent of our gene sequence with chimpanzees. This is striking evidence for chimps and chumps to have a common ancestor. 

p. 248

The Smithsonian Museum of Natural History’s website likewise states: 

DNA is thus especially important in the study of evolution. The amount of difference in DNA is a test of the difference between one species and another — and thus how closely or distantly related they are.

While the genetic difference between individual humans today is minuscule – about 0.1%, on average – study of the same aspects of the chimpanzee genome indicates a difference of about 1.2%. 

Similar statements are found in the Smithsonian itself — the nation’s museum! — visited by nearly 4 million people yearly. I took this photo in 2023 when I visited:

Photo credit: Casey Luskin.

A caption below declares that: “DNA evidence … confirms … that modern humans and chimpanzees diverged from a common ancestor…”

David Klinghoffer provides a nice rundown of other sources that have cited this statistic: 

• “We share more than 98 percent of our DNA and almost all of our genes with our closest living relative, the chimpanzee.” (Nature)
• “[A]bout 99 percent of our DNA is identical to that of chimpanzees.” (Kevin Williamson, National Review)
• “Most studies indicate that when genomic regions are compared between chimpanzees and humans, they share about 98.5 percent sequence identity.” (Scientific American)
• “Humans and chimps share a surprising 98.8 percent of their DNA.” (American Museum of Natural History)
• “[H]umans share about 99 percent of our DNA with chimpanzees, making them our closest living relatives.” (Science)
• “Chimps, Humans 96 Percent the Same, Gene Study Finds.” (National Geographic News)

This “1 percent human-chimp genetic difference” statistic has been widely promoted and is widely believed. It’s undeniably an icon of evolution. But Dr. Wells also noted that these icons are like “zombies” — they don’t die easily. Instead, they keep being repeated, long after they’ve been refuted. 

If that’s true, then don’t expect the 1 percent statistic to go away anytime soon. In fact, as I mentioned, the new Nature paper makes it very difficult to dig up the figures I’ve quoted here, so I suspect we’ll continue to see zombie numbers quoted, despite what the newly published data shows. I’ll explain all of that in more detail in a subsequent article. For the moment, suffice to say that the old 1 percent difference statistic is the latest icon of evolution to fall. May it rest in peace.