Is the Y Chromosome Disappearing? Update

The Y Chromosome is Disappearing: Is This the End of Males?
The Debate Continues Based on Few Facts and Much Speculation

by Jerry Bergman, PhD

A book published back in 2003 titled Adam’s Curse: A Future Without Men by Bryan Sykes predicted that in the future “the human race will reach the ultimate evolutionary crisis that has been millions of years in the making: The extinction of men.”[1] His prediction is that the Y chromosome will disappear, resulting in the extinction of males as we know them. Is this what is happening really?

The Y chromosome is used in all primates, most mammals, and even in some insects and plants, to produce males.[2] Some animals, such as alligators and turtles, use a complex system that enables the temperature in which embryos develop to determine the sex.[3] Already, evolution faces a problem: a defining trait of primates—the Y chromosome—is found scattered in a wide variety of lifeforms including some plants and insects. Some strange exceptions exist. Birds are ZZ/ZW and the duck-billed platypus, a mammal, boasts ten sex chromosomes![4] Specifically, platypuses

have five male-specific chromosomes (Y chromosomes) and five chromosomes present in one copy in males and two copies in females (X chromosomes). These ten chromosomes form a multivalent chain at male meiosis, adopting an alternating pattern to segregate into XXXXX-bearing and YYYYY-bearing sperm.[5]

Some rodent groups lack the Y chromosome, such as the spinous country rat[6] of Japan which also uses XO in both sexes.[7] Another problem is most all genes are differently expressed in males and females that are not on the sex chromosomes. One example is the gene vital for female growth and sexual development that encodes for estrogen receptors, ESR1, which is located on chromosome 6.

Evolutionists postulate that both bird and mammal sex chromosomes evolved from autosomal (non-sex) chromosomes.[8] How sexual life reproduced before sex chromosomes evolved is unknown, as is the far larger question, namely how did sex itself evolve![9] The standard theory is the different sex chromosomes, the X and Y in mammals, and the Z and W in birds, evolved separately from different pairs of autosomes. No evidence exists for this theory, and an analysis of the most ancient human DNA known, from Neanderthals, revealed intact X and Y chromosomes.[10] The evolution of the sex chromosomes from the autosomal chromosomes is accepted only because evolutionists cannot figure how else the sex chromosomes could possibly have originated.

The XY chromosome in the fertilized egg produces a male, and XX, even XO (Turners Syndrome) or XXX (trisomy X), all produce females. Likewise, one Y always produces a male. Even XXY (Klinefelter syndrome) produces a male with some female traits such as minor breast enlargement, illustrating the central role of the Y chromosome in determining the male sex. I reviewed this topic in 2018 (24 Feb 2018) but new claims since then indicate another visit is in order.[11]

What is the Y Chromosome and Why is It so Important?

Humans have 46 chromosomes. The structure that carries the DNA code which makes Homo sapiens human is the set of 23 somatic chromosomes, plus the two sex chromosomes, X and Y.[12] One assumption is the X and Y chromosomes were, in the past, both equal in length and in the number of genes. The theory is the male Y chromosome eventually lost nearly all of the 640 genes it once shared with the X chromosome, and the essential genes were somehow transferred to the somatic chromosomes.[13] Thus, it now has only 27 unique genes compared to thousands on most somatic chromosomes.

This idea is not based on evidence, but on speculation on both ends of the timeline: what was assumed to be true in the past and assumptions about the future – not on data. The story has produced good reasons, however, why the Y chromosome will not disappear. Conversely, other researchers speculate that it will eventually disappear. One headline supporting the disappearance opinion proclaimed, The Y chromosome is disappearing – so what will happen to men?[14] The report added, although the Y chromosome

carries the “master switch” gene, SRY, that determines whether an embryo will develop as male (XY) or female (XX), it contains very few other genes and is the only chromosome not necessary for life. Women, after all, manage just fine without one.[15]

Another headline published at about the same time as the one just cited declared, “Study Dispels Theories Of Y Chromosome’s Demise.”[16] A key fact is, in the present day, the Y chromosome is a comparatively tiny structure, about 45 total genes compared to around 1,000 on the X, as is shown in the following illustration.

The reason for the diametrically opposed positions on the disappearance of the Y chromosome is that both positions are based on speculation and very few facts. Both sides largely agree on those facts.

A New Report Published in May of 2020

Not to be outdone, Isobel Whitcomb announced the old fear in a new article in Live Science on August 30, 2020. Once again, she raised the suggestive question, “Is the Y chromosome dying out?” She added, “The Y chromosome may be in trouble.”[17] She starts with the well-known fact that if you have two X chromosomes you normally develop ovaries, and if you have an X and Y chromosome, you normally develop testes. She then admits that research only suggests it has shrunk over time.  Then she calls on evolutionary geneticists who begin their habit of storytelling:

“Our sex chromosomes weren’t always X and Y,” said Melissa Wilson, an evolutionary biologist at Arizona State University. “What determined maleness or femaleness was not specifically linked to them.” When the very first mammals evolved between 100 and 200 million years ago, they didn’t have any sex chromosomes at all. Instead, the X and Y were just like any other set of chromosomes — identical in size with corresponding structures…. animals don’t need sex chromosomes.[18]

Then, Whitcomb claims, “The only special feature of the Y chromosome is one gene, SRY, which acts as an on-off switch for the development of testes.”[19] And yet another study contradicted this claim, concluding, “A comparison of Y chromosomes in eight African and eight European men dispels the common notion that the Y’s genes are mostly unimportant and that the chromosome is destined to dwindle and disappear.” One reason for their conclusion was a finding that the worldwide genetic variation on the Y chromosome was very small compared to the comparatively large variety seen in the DNA of the non-sex chromosomes. The researchers believe that the large similarity of the Y chromosome in humans is evidence that the specific Y chromosome genes—although small in number—are very important for functions besides determining sex.[20]

The authors found that mutations are more prone to damage the 27 unique genes in the Y chromosome than in somatic chromosomes.[21] That is because the Y chromosome has no mate, thus recombination with another Y cannot occur as it does with all other chromosomes. Furthermore, as a result, “all sites on the Y are effectively linked together. Thus, selection acting on any one site will affect all sites on the Y indirectly.”[22] For detailed complex reasons I will not get into here, the study concluded, “there has to be a lot more function on the chromosome than people previously thought.”[23]

Why It is Believed that the Y Chromosome is Losing Genes

Evolutionists believe the Y is shrinking because of mutations. They know that “genes develop mutations, many of which are harmful.”[24] Meiosis separates the chromosome pairs and one way of reducing the mutational load is by recombination. This occurs when paternal and maternal chromosomes randomly mix and match, again forming chromosomal pairs. For several reasons, this process makes it more likely that only functional DNA copies will be passed on to the offspring. All chromosomes including the X (for the female XX) take part in this recombination except the Y chromosome, because the Y does not have a swapping companion: thus crossing over is normally not possible (see figure 2). Y and X chromosomes, moreover, are not similar enough to recombine, and only rarely do two Y chromosomes exist in one individual.[25]

Summary

Several salient points stand out. The first is that the literature flip-flops on the question of whether the Y chromosome is shrinking. Only a small sample of articles and papers was referenced here. One says the Y chromosome is shrinking and will eventually disappear. Another argues it is not shrinking and will, as a result, not disappear. Soon another report comes out giving new reasons for the case that the male chromosome is, in fact, shrinking, which is met by yet another study that argues for the opposite, again giving plausible reasons.[26]

All of these contradictory reports depend on a few well-supported facts that are constructed on a foundation of evolutionary assumptions. Darwinism gave birth to evolutionary imagination that is used to interpret the world, and all life in it. Evolutionists use their imaginations to envision an old, slowly-evolving world, accumulating rare beneficial mutations over hundreds of millions years that are preserved by positive natural selection, while dispensing with obsolete genetic material through negative natural selection. Usually the big problem is ignored, namely, the evolution of sex itself, and its complex systems of chromosomes, meiosis, recombination and other processes designed to produce offspring that are a blend of their parents. This, F. Lagard Smith described in 2018, is “Evolution’s fatal flaw.”[27]

References

[1] Sykes, Bryan. 2003. Adam’s Curse: A Future Without Men. New York: W.W. Norton & Co.

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

[3] Whitcomb, Isobel. 2020. “Is the Y chromosome dying out?” https://www.livescience.com/y-chromosome-dying.html.

[4] Grützner, Frank, et al. 2004. In the platypus a meiotic chain of ten sex chromosomes shares genes with the bird Z and mammal X chromosomes. Nature 432:913-917.

[5] Grützner, et al., 2004, p.  913.

[6] “Sex Chromosomes: Why the Y Genes Matter”. 2015. Science 2.0, May 30.

http://www.science20.com/news_articles/sex_chromosomes_why_the_y_genes_matter-155840

[7] Graves, Jennifer A. Marshall. 2006. Sex Chromosome Specialization and Degeneration in Mammals. Cell 124(5):901-914, March 10, p. 912.

[8] Grützner, 2004, p.  913.

[9] Smith, F. LaGard. 2018. Darwin’s Secret Sex Problem: Exposing Evolution’s Fatal Flaw—The Origin of Sex. Bloomington, IN: WestBow Press.

[10] Pääbo, Svante. 2015.  Neanderthal Man: In Search of Lost Genomes. New York: Basic Books, pp. 179-181, 243.

[11] Bergman, Jerry. 2018. “Is the Y Chromosome Disappearing?” Creation-Evolution Headlines, February 24. https://crev.info/2018/02/y-chomosome-disappearing/

[12] Griffin, Darren and Peter Ellis. 2018. “The Y chromosome is disappearing – so what will happen to men?” The Conversation, January 17. https://theconversation.com/the-y-chromosome-is-disappearing-so-what-will-happen-to-men-90125

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

[14] Griffin, Darren. 2018. “The Y chromosome is disappearing – so what will happen to men?” PhysOrg, January 18.  https://phys.org/news/2018-01-chromosome-men.html.

[15] Griffin, 2018.

[16] Sanders, Robert. 2014. “Study dispels theories of Y chromosome’s demise.” Berkeley News January 9. https://archaeologynewsnetwork.blogspot.com/2014/01/study-dispels-theories-of-y-chromosomes.html.

[17] Whitcomb, 2020.

[18] Whitcomb, 2020.

[19] Whitcomb, 2020.

[20] Sayres, Melissa A. Wilson, et al. 2014. Natural Selection Reduced Diversity on Human Y Chromosomes. PLOS Genetics, January 9.

[21] The number given varies. The National Human Genome Research Institute states that “the X chromosome is about three times larger than the Y chromosome, containing about 900 genes. While the Y chromosome has about 55 genes. “ https://www.genome.gov/about-genomics/fact-sheets/X-Chromosome-facts. Evidently the actual number in not known.

[22] Sayres, et al., 2014.

[23] Sayres, et al., 2014.

[24] Whitcomb, 2020.

[25] Whitcomb, 2020.

[26] “Why the ‘wimpy’ Y chromosome hasn’t evolved out of existence.” ScienceDaily, August 6.
https://www.sciencedaily.com/releases/2020/08/200806111839.htm

[27] Smith, 2018.

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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.