Ape and Human Y Chromosomes Compared
New genetic differences attributed
to evolution, but evolutionary bias
ignores designed function
by Jerry Bergman, PhD
Some of the most important examples of claimed evidence for the evolution from ape to human are generic comparisons. The chimpanzee–human, last-common ancestor shared by the extant Homo (human) and Pan (chimpanzee and bonobo) genera of Hominini, is estimated to have diverged from five to thirteen million years ago. The difference between these two date estimates is 2.6 times, which reveals that they are more of a guess than an estimate.[1]
A serious problem is that the comparisons are not between modern humans and apes that lived 13 million years ago, but apes and humans that are living today contemporaneously at the same time in history.[2] Given the assumptions of evolution, since humans are higher than apes on the evolutionary scale, it is logical that apes would also have evolved in the direction of humans as time has progressed. The reason is since natural selection functioned in a savanna environment to evolve humans, the same natural selection environmental factors should have also operated on apes 13 million years ago.
Ideal comparisons would be between modern humans and apes that lived 13 million years ago, when both began evolving from their long lost common ancestor. This raises the following question: why did one ape-human common ancestor evolve to branch off into humans while the other members of the “common ancestor” type continued largely as apes and evidently not evolving at all? Why didn’t these common ancestors also evolve in the direction of humans instead of remaining apes, as taught by evolutionists? Because evolutionists believe we have evolved from the common ancestor, our genome originally was the common ancestor genome, as was the ape branch genome of 13 million years ago. As illustrated in the study reviewed below, the same problems exist when comparing different higher primates using genetic analysis.
The Makova research
Ignoring the problem discussed above, a recent sequence of the complete X and Y chromosomes of the living great apes was compared with the human Y chromosome, which was sequenced 21 years ago. Specifically, the newly generated, complete “end-to-end” reference genomes for the sex chromosomes of five great ape species and one lesser ape species was completed.[3] Of note is that the living great ape species that were studied are all now endangered (Penn State, 29 May 2024).
Problems in making comparisons
The Y chromosome has always been challenging to sequence because it contains many repetitive regions (such as TGCTTGCC*TGCTTGCC*TGCTTGCC*TGCTTGCC*TGCTTGCC). The sections have been spaced by a * in my example to illustrate the repetitive region concept. Because traditional, short-read, sequencing technology decodes sequences in short bursts, and then assembles the segments together, it is difficult to place the resulting segments in the correct order. Another problem is the X and Y chromosomes do not exist in pairs in males as do the XX in females. Thus, neither chromosome in males exchanges genetic information with its mate chromosome. This results in the accumulation of many deletions, repetitive elements, and other mutations contributing to the increase of the mutational load in males but not a similar increase in females.[4]
Evolutionists often explain genetic differences by concluding that evolution created these genetic differences. More importantly, though, is the body-design difference which is produced by the genetic difference. The functional explanation is that the genetic difference produces muscle differences in humans, for example the much more complex face musculature in humans, which is why only humans can laugh and smile and apes cannot.[5] The human face possesses around 30 muscles on each side[6] compared to a chimp which has only 23 muscles on each side of its face.[7]
Findings related to the evolutionary claims
One finding of the Makova genetic analysis was a much larger than expected difference between the five primates compared. The researchers did detect some homology (similarity) between Y chromosome ampliconic regions (a segment of chromosomal DNA that has many genetic repeats) but only in DNA pairs of closely related species. Examples given include differences between the bonobo and chimpanzee, and between B. orangutan and S. orangutan. Although similar, these regions still differed significantly.
A creationist explains these differences as a product of functional design. Evolutionists explain them by postulating extremely rapid evolution, which would explain only the genetic contrasts and not the morphological differences. Another finding was that, in contrast to centromere X, which was stable throughout primate evolution, the chromosomal position of centromere Y varies, depending on the animal. Creationists would interpret this finding as a much more varied design for the chromosomal position of centromere-Y, in contrast to centromere X, where its design did not change in the primates evaluated. The reason for these design differences requires a more detailed study, but likely relate to design modifications necessary for effective operation of the specific system of concern in primates. The authors concluded that
Our complete assemblies have revealed the evolution of great ape sex chromosomes in unprecedented detail. In contrast to the X chromosome, the Y chromosome has undergone rapid evolution in all ape species. It has accumulated repetitive elements and experienced elevated rates of nucleotide substitutions, intrachromosomal rearrangements and segmental duplications, probably owing to the loss of recombination over most of its length.[8]
A creationist would summarize the results of the Makova et al. study, looking at design differences, as I have below:
Our complete assemblies have revealed many major design differences in the great ape sex chromosomes in unprecedented detail. In contrast to the X chromosome, the Y chromosome design varies greatly in the ape species evaluated including repetitive elements and nucleotide, intrachromosomal and segmental differences. The next step is to determine the reason for these design differences found in the primate research. (Emphasis added.)
Summary
The Makova chromosomal analysis of the design differences were explained as due to evolution. In contrast, the creation explanation would focus on the reason for the system design differences for the genetic comparisons. Explaining a design difference due to evolution does not explain the purpose or function of the difference, which should be the research focus. Noting only gene differences implies that random mutations are at the heart of evolution. Detailing the designs that result from the gene code differences would support the idea of purposeful design. The idea that the function of the design variations was due to evolution which just happened to improve the function of some body part is fallacious. That same thinking once labeled body parts which had unknown functions “vestigial organs”, but now, those very same body parts are explained by their functional design and their role in biological organization.
References
[1] Mann, A. and M. Weiss, “Hominoid phylogeny and taxonomy: A consideration of the molecular and fossil evidence in an historical perspective,” Molecular Phylogenetics and Evolution 5(1):169–181, doi:10.1006/mpev.1996.0011, 1996.
[2] Mrnason, U,, A. Gullberg, and A. Janke, “Molecular timing of primate divergences as estimated by two nonprimate calibration points,” Journal of Molecular Evolution 47(6):718–727, December 1998.
[3] Makova, K., and G. McCormick, “Complete X and Y chromosome sequences of living great ape species determined.” https://www.psu.edu/news/eberly-college-science/story/complete-x-and-y-chromosome-sequences-living-great-ape-species/?utm_placement=newsletter, 29 May 2024.
[4] Makova, K., and 64 co-authors, “The complete sequence and comparative analysis of ape sex chromosomes,” Nature 630:401-411, p. 404. 13 June 2024.
[5] Burrows, A., et al. “Muscles of facial expression in the chimpanzee (Pan troglodytes): Descriptive, comparative and phylogenetic contexts,” Journal of Anatomy 208(2):153–167, February 2006.
[6] Westbrook, K.E., T.A. Nessel, M.H. Hohman, and M. Varacallo, Anatomy, Head and Neck: Facial Muscles, Treasure Island, FL: StatPearls Publishing, 20 April 2024.
[7] Burrows, A., et al., 2006.
[8] Makova, et al., 2024, p. 409.
Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology for over 40 years at several colleges and universities including Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,900 publications in 14 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,800 college libraries in 27 countries. So far over 80,000 copies of the 60 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.