Because mammalian eggs are produced early in life, while sperm are created continuously, fathers are responsible for a greater share of new mutations passed down to their offspring than mothers. This slightly complicates genetics-based time-since-last-common-ancestor estimations, leading to recent results to the effect that the human-chimp split happened about twice as far back as previously thought. Adam Benton has more information, if you’re interested.
This new paper has prompted Jeffrey Tomkins, the ICR’s go-to geneticist, to publish “Chimp DNA Mutation Study–Selective Yet Surprising.” Tomkins is known for contesting the typically-cited genetic similarity figures of 94-99% and having calculated using his own method a “conservative” (i.e. maximum) figure of nearer 70%.
There are various ways in which mutations modified the genome of the last common ancestor of humans and chimps in each group since that time. On the one hand (the left one in this case) they modified, added, or deleted individual nucleotides, which leaves a signature in these comparisons in the form of single nucleotide differences. A percentage difference can be calculated and knowing the rate of these changes (and accounting for things like the difference between the contribution of males and females) we can determine the amount of time it took.
On the other hand mutations can also modify large sections of DNA, physically moving, reversing, adding, and deleting them. When DNA has been removed or added in one lineage but not the other, like in the above, we would get a section that does not “align,” or align poorly. These sections are important when considering the overall picture of differences between two species’ genomes, but are rightly discarded when percentages and splitting times are calculated.
To Jeffrey Tomkins and his supporters this is apparently a conspiracy – the selective omission of contrary evidence. His own research derives the 70% figure in part by leaving some of these sections in. The trouble is that sections that don’t align aren’t comparable: the deletion of a continuous segment of 1000 bases are not equivalent to 1000 individual nucleotide deletions, because the former can be removed a single stroke – they amount to a single mutation, and happen by a different mechanism at a different rate to the latter variety. Tomkins is entitled to think that his figure is a more honest reflection of the true differences between humans and chimps at the genetic level if he wants to – but more on that some other time, maybe – but it is not useful when we want to calculate how long ago humans and chimps split from each other.
Indeed, the 2013 Answers Research Journal paper of his that Tomkins cites here actually looks chromosome-by-chromosome at the percentage of DNA sequences that align well (and not including those that don’t align at all). It does not even look at, on the other hand, individual nucleotide differences. Because of that this data, while not uninteresting, is nevertheless entirely irrelevant to the question of how long ago the most recent common ancestor lived.
Which brings us to what he says today:
The researchers then compared selected DNA segments between chimpanzee and human that were highly similar, omitting the many non-similar regions. They state, “In the intersection of the autosomal genome accessible in this study and regions where human and chimpanzee genomes can be aligned with high confidence, the rate is slightly lower (0.45 × 10−9 bp−1 year−1) and the level of divergence is 1.2%…implying an average time to the most common ancestor of 13 million years [page 1274, emphasis added].” There are basically two notable points from this summary statement that I will address.
The first important point is that the comparative data was clearly cherry-picked—the scientists only used the regions that were about 98% similar and essentially threw out everything else. These are the regions that the researchers stated “can be aligned with high confidence.” It appears that all the dissimilar DNA regions got tossed out because they didn’t fit the evolutionary paradigm and would have made the whole idea of chimps evolving into humans completely impossible.
He is, as I said, insinuating conspiracy. And quite the conspiracy it must be, if the facts are in the open yet “seldom discussed”:
It was initially noted by another group of evolutionary scientists that when comparing random chimp genomic sequence only “about two thirds could be unambiguously aligned to DNA sequences in humans.” In confirmation of this widely known, but seldom discussed, inconvenient fact among those evolutionists working in the field was a comprehensive study published in 2013 by this author.3 In that research, I compared each individual chimpanzee chromosome to human (piece-by-piece) and it was shown that the chimpanzee genome was only 70% similar on average to human, with only short regions being highly similar.
As you can see, he thinks his 70% paper is relevant here. It isn’t.