I am an Elder at a small church in rural Maine and I am trying to educate my self on common decent.
One of the most common objections to common descent (that I am positive I will encounter in my congregation) is that the 98% similarity comes from a comparison of only 2.5% (the proteins coding) part of the genome.
I understand that this is a misrepresentation (or perhaps is just incorrect), but I haven’t been able to find a good resource that explains the whole issue.
Would some one please point me in the right direction?
First off, it’s not 98%; it’s 98.77%. Second, it’s not just protein-coding genes, it’s all the sequences in about 85% of the genome, and later, more complete sequencing hasn’t changed that figure. Protein-coding sequences, as you mention, are only about 2% of the genome, but they’re actually 99.5% similar.
The 98.77% figure refers to point differences — A vs. G, C vs. T, and so on — in sites that can be aligned between species, i.e. that we can say are the same spot. It doesn’t count long or short pieces, called “indels”, that only occur in one of the species. Those make up about 5% of the combined genomes. There are about 35 million site differences between the species and around 5 million indels of various lengths.
John’s answer is already better that I could do, but as I’m sure you know, coming up with bad arguments is easier than understanding good results. My best general response is simply to point out that science works producing useful results.
I think I need to be more clear in my questions lol.
The number I am looking for isn’t the percent similarity or difference between the two genomes.
I am trying to find the percent of the genomes that were used in the comparison.
You mentioned that, in that particular paper, about 85% of the genomes were compared, but comparisons at higher percents have been made and the results have been consistent.
I curious as to what has been the largest percentage of the genomes that have been compared?
I tagged Steve Shaffner (Glibsnort) who was a co-author of the 2005 paper. If anyone can give you a better answer, he can, but he doesn’t post here often.
This article is from the blog of Richard Buggs, summarizing a discussion on this question at Biologos a few ago (where Steve S. responds):
I think Buggs may be wrong about the usual estimate of 98.77% similarity. He claims that it includes one-base indels, but I think it includes only SNPs. Also, I don’t think that overall similarity that counts indels is a useful measure. We should count, if anything, the number of mutations separating the species, and an indel of 1000 bases is just one mutation. We differ by 35 million SNPs and 5 million indels. That’s the best comparative measure.
Hi all, here’s a really new paper out with some nice comparative data from eight primate species, including human, chimp, and bonobo, and providing several new full genome assemblies. If nothing else, this and several other recent papers (look for the two Zoonomia special issues in Science last year) show that we can now talk in detail about how the genomes differ instead of tossing out crude numbers about “similarity.”
People trying to refute the evidence for common ancestry of humans and chimps tend to argue that the percentage similarity Is Really Not That Big. Even if they were right about that, the greater similarity of humans with chimps and bonobos that with Gorillas (and even less with Orangs) continues to be evidence for common ancestry. They usually do not look at that comparison.
AS you know, Dan, I’m not a biologist nor even a scientist, just a retired engineer. I would say that Josh needs to understand first and foremost that resistance that he gets will NOT really be about science. It will be about concordism, both historical and scientific concordism. That concordism is generally not ever understood to be an axiom these churches operate under - it’s so ingrained that it is seen as “the biblical view.” The people they have been taught to trust and have learned to trust are all concordists. I can share some approaches I have tried but it is a tough sell for them and it’s not anything that many of them will reconsider - at least not quickly.
