Over the last few days we have broken a major story about a recently published Nature study which shows that the human and chimp genomes are 14.0 percent to 14.9 percent different. After explaining the technical details of this calculation, and noting that these genetic differences cannot be dismissed as simply reflecting highly mutable junk DNA, we're now ready to ask the big question: What does this mean for evolution, common ancestry, and intelligent design? Unfortunately, it may be premature to seek definitive answers at this point -- although, as we'll see, it's clear that this type of evidence does not bolster common ancestry over common design. What's also clear is that the old icon of evolution that we are only 1 percent genetically different from chimps is overturned by this evidence.

Now that we have a much better grasp of the total degree of genetic differences between humans and chimps, it may be possible to do an analysis of whether there is enough time in the fossil record for these genetic differences to evolve by random mutations and other unguided evolutionary mechanisms. We often call such an inquiry a "waiting times analysis."

Unfortunately, this analysis will be complicated by the fact that many the differences go beyond mere point mutations that could be studied through a relatively straightforward molecular clock analysis. From an evolutionary perspective, many of the large-scale "gap differences" between humans and chimps represent insertions, deletions, duplications, inversions, and other large-scale mutations. In order to do a waiting times analysis, one would have to calculate how often such mutations arise, and the likelihood of them arising by unguided evolutionary mechanisms in the time allowed by the fossil record (usually given as about 4 to 8 million years since our supposed most recent common ancestor we shared with chimps).

It may be a challenging analysis, but now that we have the necessary raw genome sequence data, at least we could start thinking about how to do it.

What About Common Ancestry?

The next question one would want to address is the question of the implications for human-ape common ancestry. As I explained in my first post, quite a few evolutionists have used the supposed 99 percent genetic similarity / 1 percent genetic difference between humans and chimps to argue that we therefore must share a common ancestor. Now that this icon of evolution has been exploded by the evidence, it will be interesting to see if evolution-apologists continue to try to make this argument.

But what if it had turned out that we really are only 1% genetically different from chimps? Would this make for an argument for common ancestry? The answer is "No."

No one questions that humans and chimps have huge portions of their genomes, especially certain protein-coding regions, that are highly similar -- even only 1 percent different. But this does not make for an argument for common ancestry. Whatever the degree of similarity, they could reflect common design based upon a common blueprint as much as they could reflect common descent. As I wrote a few years ago:

The case for human-chimp common ancestry is further significantly weakened once one realizes that there are other potential explanations for functional similarities: notably, design based upon a common blueprint.

Intelligent agents often re-use parts and components that perform common functions in different designs. It's a good engineering design principle to follow! Everyday examples of this include wheels used on both cars and airplanes, or touchscreen keyboards used on both phones and tablets.

It should be noted that common design, as an argument, is not intended to prove species were specially created or designed separately. Rather, it's a rejoinder put forth to defeat the evolutionist assertion that genetic similarity necessarily indicates common ancestry. Genetic similarity doesn't necessarily indicate common ancestry because intelligent agents can and do independently use common parts in different designs to fulfill common functional goals. High genetic similarity could reflect design with a common blueprint rather than common ancestry.

Thus, as I further explained, the percent genetic similarity between humans and chimps really does not address the question of whether the two species are evolutionarily related:

Whatever the exact percentage of human-chimp genetic similarity (however you want to measure it) turns out to be, let's grant that it will be fairly high, probably 84 percent or greater. Does this necessarily require the conclusion of common ancestry? Is the case for common ancestry, based upon the degree of similarity, an objective or rigorous argument that's capable of being falsified? For example, if a 1 percent genetic difference implies common ancestry, but then that statistic turns out to be wrong, then does a 4 percent genetic difference mean common ancestry is false? How about 7 percent or 10 percent genetic difference? 25 percent? At what point does the comparison cease to support common ancestry? Why does the percent genetic similarity even matter? It's not clear that there is an objective standard for falsification here, any identifiable reason why a particular percentage of genetic similarity should be taken to indicate common ancestry.

Here was my conclusion: "the 'percent genome identity' [i.e., percent genomic similarity between humans and chimps] provides no rigorous argument for common ancestry and does not answer many very interesting questions within this particular debate."

At Least Get the Facts Straight

Nonetheless, as I noted, evolutionists have repeatedly asserted over the years that genetic similarity necessarily indicates common ancestry. In my earlier post, I quoted Bill Nye stating 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." I also noted that even the Smithsonian Museum of Natural History in Washington, DC, quotes the same statistic that human and chimp DNA is "98.8 genetically similar," telling the public that "DNA evidence ... confirms ... that modern humans and chimpanzees diverged from a common ancestor..."

After the publication of this recent Nature paper, you can't accurately make those kinds of statements anymore without also acknowledging that some 12.5 percent to 14 percent of the chimp and human genomes are so different that they can hardly be compared, and may even represent sections that are simply absent in the other species' genome. Call them the result of "highly mutable" sections of the genome or whatever other interpretation you like. But they can no longer be ignored. After this paper, if you want to talk about the degree of similarity between the human and chimp genomes, and you claim the human and chimp genomes are only 1 percent different without mentioning the huge sections -- 12.5 percent to 14 percent that are completely different -- then you're saying something that simply is not true.