October 9, 2020 | Jerry Bergman

Neanderthal Y Chromosome Looks Modern

 

No evidence of the disappearing Y chromosome:
Another theory bites the dust

by Jerry R. Bergman, PhD

A new study analyzed the genome of what they termed “our closest relatives, Neanderthals and Denisovans,” which were then compared with modern humans.[1] Most previous Neanderthal DNA research has been on females because the X chromosome preserves better than the fragile Y. Fortunately, a team of geneticists from the United States, China and Europe were able to study the male Y chromosomes from three Neanderthals and two Denisovans. The team found from their limited sample that the modern human and Neanderthal Y chromosomes were more closely related to each other than the Neanderthal and the Denisovan Y chromosomes.[2] They concluded that Homo sapiens and Neanderthals were more similar genetically than were the Neanderthal and the Denisovian. The U.S. National Library of Medicine summary presented the conventional evolutionary explanation by writing the following:

Neanderthals were very early (archaic) humans who lived in Europe and Western Asia from about 400,000 years ago until they became extinct about 40,000 years ago. Denisovans are another population of early humans who lived in Asia and were distantly related to Neanderthals. (Much less is known about the Denisovans because scientists have uncovered fewer fossils of these ancient people.) The precise way that modern humans, Neanderthals, and Denisovans are related is still under study. However, research has shown that modern humans overlapped with Neanderthal and Denisovan populations for a period, and that they had children together (interbred). As a result, many people living today have a small amount of genetic material from these distant ancestors.[3]

Myth: The Y Chromosome Will Eventually Disappear, Resulting in Male Extinction

X and Y chromosomes differ dramatically in size and content

Given the dates scientists claim Neanderthals and Denisovans lived, from 400,000 to 40,000 Darwin-years ago, one would expect evidence for the shrinking Y chromosome prediction. Yet as far as we can tell, in 400,000 to 40,000 Darwin years, the Y chromosome has not changed one iota in length.

The Y chromosome is used in all primates, most mammals, and even in some insects and plants, to produce males.[4] The assumption that the Y chromosome will disappear is based on the theory that it originally evolved from a much larger autosome chromosome. The evolution of the sex chromosomes from the autosome chromosomes is postulated largely because evolutionists cannot figure how else the sex chromosomes could possibly have originated.

Thus, evolutionists assume that the X and Y chromosomes were once both equal in length and in the number of genes. The theory postulates the male Y chromosome lost nearly all of the 640 genes it once shared with the X chromosome. Furthermore, the essential genes once on the X chromosome were somehow transferred to the somatic chromosomes.[5] As a result, the theory concludes, the Y chromosome in humans now has only 27 unique genes compared to thousands on most somatic chromosomes.

The 2020 Study by Martin Petr, et al.

The 2020 study by Petr, et al. did not focus on the length of the Y chromosome, but rather on comparisons of Neanderthals and modern humans. Nonetheless, they did not find evidence that the 400,000 to 40,000 Darwin-years-old Neanderthal and Denisovan Y chromosomes were significantly longer than those of modern man, which would be expected if the Y chromosome was shrinking. They did find evidence of what are evidently minor differences between the Neanderthal and the Denisovan Y chromosomes.

The Cause of the Differences Found

Geneticists expect major differences in 40,000 to 400,000 Darwin-years-old Y chromosomes due to damage to DNA by the ubiquitous background ionizing radiation on the Earth’s surface. The radiation is from both geophysical sources (in soil minerals including potassium, uranium and thorium and their decay products) and astrophysical sources (such as cosmic radiation). These sources of ionizing radiation disintegrate DNA which is constantly repaired in living organisms. Once the creature is dead, however, DNA is no longer repaired. Consequently, DNA damage accumulates.[6] They explain away the lack of accumulated damage with over such long periods of time by affirming their deep-time belief. They say that although

DNA is a relatively weak molecule’ comparatively speaking, yet under certain conditions it persists in the fossil record.[7]

DNA showing ultraviolet damage to the base-pair bonds. (Wiki Commons)

The researchers noted that “Neanderthals have been shown to have accumulated an excess of deleterious variation compared with modern humans” which may account for some of the genetic differences found. This is the opposite of what we would expect due to the mutation accumulation trend seen today.  One speculates that the “deterioration” occurred due to damage by radiation-caused mutations. This caused the difference found in the Petr, et al. study, especially considering the claim that the Y chromosome DNA tested were from 400,000 to 40,000 Darwin-years old.

The researchers wrongly predicted that Neanderthal Y chromosomes would still have the primitive DNA and “will therefore be more similar to Denisovans than to modern humans.”[8] What was found was

like maternally inherited mtDNA, modern human and Neanderthal Y chromosomes were more related to each other than to the Denisovan Y…. all but the earliest Neanderthal mtDNA samples are far more similar to those of modern humans than to those from Denisovans.[9]

[Ancient] nuclear and mtDNA sequences revealed phylogenetic discrepancies between the three groups that are hard to explain”

Hard to explain, that is, by evolution. But the data make sense given what we know about mutations.[10]

Problems with the Study

One problem with the study is the small sample size. This is expected due to the fact that virtually none of the male Neanderthal and Denisovan remains studied so far have contained well-preserved Y chromosome DNA. The problem of DNA preservation is enormous. Even in cases where the body was known to be buried only a decade ago the DNA is often close to worthless.

Another problem is the time span. If the samples were actually 400,000 to 40,000 years old—based on mutation rates documented in contemporary studies—the DNA would have long deteriorated to the point that few organized DNA strands would have remained even under good preservation conditions. Professors Meisenberg and Simmons note that the

mutational load is kept in check by natural selection.  In most traditional societies, almost half of all children used to die before they had a chance to reproduce. Investigators can only guess that those who died had, on average, more “mildly detrimental” mutations than those who survived.[11]

Sanford’s book examines the impact of near-neutral mutations that are invisible to selection.

Mutations are widely recognized as a major cause of many diseases, including cancer and heart disease. An estimated 99.9% of all mutations are, in the long run, harmful. In a review of the mechanisms that drive genetic degeneration, Charlesworth and Charlesworth concluded that “most mutations with observable phenotypic effects are deleterious.”[12] Estimates vary greatly, but generally, around one new mutation occurs in “each round of cell division, even in cells with unimpaired DNA repair and in the absence of external mutagens.”[13]

As a result, for germ-line mutations, “every child is born with an estimated 100 to 200 new mutations that were not present in the parents.”[14] Cornell University Professor John Sanford puts the number of point mutations at about 200 in each generation, and for all new mutation types the number is closer to 1,000 in each generation.[15] Given this data, the fact that some intact DNA strands still exist in the Y chromosome is evidence that they are not nearly as old as claimed.

Summary                                                                                                                                 

This study is one of many that is slowly filling in our knowledge about human life on the early Earth. As the evidence builds, the trend is supporting, not evolution, but a creation worldview. I am looking forward to the next research studies in this self-correcting enterprise called Science.

Packing 6 feet of DNA into a cell nucleus is a highly complex process. (Wiki Commons). See the Illustra film, “18 Trillion Feet of You” to see how it is done.

References

[1] Sci-News News Staff. 2020. Scientists Sequence Y Chromosome DNA of Denisovans and Neanderthals. Sci-News,. September 25. http://www.sci-news.com/genetics/denisovan-neanderthal-y-chromosome-dna-08888.html

[2] Petr, Martin; et al. 2020. The evolutionary history of Neanderthal and Denisovan Y chromosomes. Science 369(6511):1653-1656. doi: 10.1126/science.abb6460.

[3] U.S. National Library of Medicine. 2020. What does it mean to have Neanderthal or Denisovan DNA? Genetics Home Reference, August 17. https://ghr.nlm.nih.gov/primer/dtcgenetictesting/neanderthaldna. [Not a stand-alone website as of October 1, 2020.]

[4] Haskett, Dorothy R. 2015. “The Y-Chromosome in Animals”. The Embryo Project Encyclopedia, May 28. https://embryo.asu.edu/pages/y-chromosome-animals

[5] Hughes, Jennifer F., et al. 2015. Sex chromosome-to-autosome transposition events counter Y-chromosome gene loss in mammals. Genome Biology 16,Article number 104, May 28. https://phys.org/news/2015-05-sex-chromosomeswhy-genes.html

[6] Mitchell, David; Eske Willerslev and Anders Hansen. 2015. Damage and repair of ancient DNA. Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 571(1-2):265-276.

[7] Poinar, Hendrik N. 2002. The Genetic Secrets Some Fossils Hold. Accounts of  Chemical. Research.  35(8): 676–684, February 2. https://pubs.acs.org/doi/abs/10.1021/ar000207x.

[8] Sci-News News Staff, 2020.

[9] Sci-News News Staff, 2020.

[10] Sci-News News Staff, 2020.

[11]Meisenberg, Gerhard and William H. Simmons. 2006.  Principles of Medical Biochemistry.  2nd edition.  Linn, MO: Mosby/Elsevier, p. 153.

[12] Charlesworth, Brian and Deborah Charlesworth. 1998. Some evolutionary consequences of deleterious mutations.”  Genetica, 102/103:3-19, p. 3.

[13] Meisenberg and Simmons, 2006, p. 153.

[14] Meisenberg and Simmons, 2006, p. 153.

[15] Sanford, John. 2014. Genetic Entropy. 4th edition Lima, NY: Ivan Press.


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 1,300 publications in 12 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,500 college libraries in 27 countries. So far over 80,000 copies of the 40 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.

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