Do Humans and Chimpanzees share a Common Ancestor? Chromosome 2 Fusion (Irrefutable Evidence?)
48#evolution #creation #christianity #origins #debate #apologetics #science #genetics
Apologists of evolutionary theory look to the apparent chromosome 2 fusion in humans as evidence for common descent. When this argument is examined, it becomes evident that this is a dispute largely agnostic to the overall ancestry debate. In other words, looking to a possible chromosomal fusion in the human lineage as a way to differentiate (or discriminate) between the creation and evolution models will not work. This is simply because both models can account for the data. As a matter of fact, the Biblical model of ancestry provides the more parsimonious (the simplest) answer.
The Biblical creation model comprises 2 bottlenecks post-Flood. Right after the Flood, the human population is 8 (Noah, his wife, Shem, Ham, Japheth, and their wives). People don't spread out around the planet right away. This means we have several hundred years where humans are mostly situated in a single geo-graphical location (rather than spreading out to different parts of the planet). At the tower of Babel, we see most of the human population (some isolated human families may have spread out prior to Babel, but the Bible appears to be silent on this) isolated to one major area. God then confuses the languages which results in people spreading out and filling the earth. This time period from when Noah and his family walk off to Ark to the tower of Babel dispersal could explain how a fusion could become fixed in the population before people move out around the planet. In other words, the separate ancestry model can better explain why all humans today have 46 chromosomes rather than 48 (if they were created with 48 chromosomes).
This is not to say there really was a fusion in the human lineage. I am simply pointing out the agnostic nature of this argument that defenders of common descent argue is undeniable evidence for their viewpoint. There exists scientific evidence against a fusion. One of the biggest reasons proponents of evolution believe there are traces of an ancient fusion in the human genome involves telomeric repeats. But finding head-to-head telomeric repeats in a human chromosome cannot be irrefutably interpreted as being the result of a fusion. It turns out these elements are found within the human genome at locations not applicable to a fusion. They simply represent functional stretches of DNA fulfilling a purpose to the overall management of the human genome.
If these telomeric calling cards (in a head-to-head arrangement) were only found at the reputed fusion site, the evolutionary community may have a point. For awhile this was thought to be the case. A fellow Young Earth Creationist and myself discovered telomeric-sequences in a head-to-head (the so-called calling cards of a fusion) arrangement at other locations within the genome that are not pertinent to an ancient fusion. This was a novel discovery. It also adequately answers an evolutionary challenge.
The head-to-head arrangement of repetitive telomeric DNA (TTAGGG/CCCTAA) has now been demonstrated to not be completely unique to the so-called fusion site—as these DNA elements have been found in other places within the human genome.
The innovative research performed by a fellow Young Earth Creationist and myself has resulted in compelling evidence for telomeric repeats (interstitial or internal telomeric sequences) in both forwards and in reverse existing on multiple chromosomes (1, 2, 6, 9, 10, 15, 16, 18, 20).
Most importantly, we also discovered a similar signature in chromosome 9. The telomeric-like hexamer sequence and its reverse complement are arranged head-to-head in a similar fashion to the purported fusion site. Was the reputed fusion site cherry-picked? It appears so. It is important to note that chromosome 2 is moreover the second largest chromosome in the human genome. Chromosome 9 is much smaller, and yet it contains fewer gaps between the telomeric repeats, with the chromosome 2 site containing numerous gaps. The asserted fusion site is only 798 bases in length. If this really was the mark of an ancient fusion event, this region should be much larger than 798 bases. There are only roughly 10 intact TTAGGG telomere sequences that exist at the site. And there are only about 43 of the reverse complement telomere sequences that are recovered intact.
In summary, the chromosome 2 fusion argument does not provide the evolutionary community with discriminatory evidence for common descent. If there was a fusion event in the human lineage, the Biblical model of ancestry can easily account for it. As a matter of fact, the separate ancestry model can better account for it! The evolutionary community has to address both the fixation problem for a fusion as well as the good evidence against a fusion happening at all.