How DNA Is Packaged in Sperm Cells
No Evidence Exists for Sperm Evolution:
More Complex than Assumed
Just a Few Months ago
by Jerry Bergman, PhD
Part III: Sperm Design vs Evolution
Sexual reproduction requires both the male seed, sperm, and the female seed, ovum, collectively called gametes. Orthodox evolutionary theory postulates that all life-forms, and all organs, have evolved, and this includes sperm.
A computer search for the evolution of sperm provided many articles on the development of sperm in the testicles, but a rare few about the evolution of sperm from some primitive non-sperm precursor. One article, titled On the Origin and Evolution of Sperm Cells[1] covers the failed attempts to discern the evolutionary origin of sperm, noting that
Sperm cells have intrigued biologists since they were first observed nearly 350 years ago by Antonie van Leeuwenhoek and Johan Ham. The discovery of these ‘animalcules’ (i.e., spermatozoa) launched the field of sperm biology, and the subsequent three and half centuries of inquiry into this small, highly specialized cell has revolutionized our understanding of reproduction and fertilization. An extraordinary diversity of sperm morphology and behavior has been observed across the animal kingdom, and the complexity of the molecular and physiological processes that occur as sperm develop, mature, and then eventually undergo their extraordinary journey to find and fertilize an egg continue to intrigue and inspire biologists to this day.[2]
No ideas were included in Fisher’s report that attempted to explain the evolution of sperm from non-sperm, even though approximately 250 publications each year are on the subject of sperm competition alone.[3]
From Asexual to Sexual: How?
The evolution of how asexual reproduction evolved into sexual reproduction is a critical, but unsolved, area of biological evolution.[4] Part of this area is the evolution of the gametes, sperm and eggs, but the articles reviewed from an internet search largely ignore the topic. Fisher admits that “one of the central mysteries of evolutionary biology [is] why do separate male and female gametes exist?”[5]
She mentions that sperm competition, or the precursor of what became sperm competition, “drives the evolution of gamete dimorphism.”[6] This observation ignores the fact that sexual reproduction cannot occur until gamete dimorphism (meaning a sperm and an egg have evolved) and a means to bring the two together, exists. The claim that “A major consequence of gamete dimorphism is sperm competition, where the smaller gamete competes for the larger gamete” does not support evolution from a non-gamete to a gamete. It is only an example of the main function of natural selection in life, which is to reduce deterioration of a structure and fine-tune it.[7]
The Requirement to Package and Repackage the DNA
Evolutionists must account for the fact that paternal chromosomes are required to make a radical conformational change during sperm development. Paternal chromosome compaction to pre-fertilization sperm includes the requirement of both superior hydrodynamic performance of sperm, and the preservation of paternal genome integrity in the sperm head.
Ultracompaction is used to reduce the space from 20- to 200-fold to achieve the space requirement for DNA and to prevent replication during its trip to the egg. This process of ultracompaction of sperm DNA is “associated with genome-wide replacement of histones with protamines, but the actual role of this radical change in chromatin organization remains largely enigmatic.”[8] The importance of this step is illustrated by the fact that “the global replacement of histones with protamines in sperm chromatin is widespread in animals, including insects.”[9] Histone removal in this important role includes protecting paternal chromosomes and protecting paternal chromosomes from premature division at fertilization.[10]
A diagram illustrating histone function in assembling the DNA. From Wikimedia Commons.
Protamine is a major core protein of spermatozoa. It functions as a DNA binder causing DNA compaction in the nucleus of spermatozoa heads. It is vital for the chromatin formation required for the functions of spermatozoa. This was confirmed by earlier research finding that “protamine deficiency instigated a severe disruption of spermatogenesis affecting male infertility. In addition, the protamine expression disorder caused a decrease in number, motility, and morphology of spermatozoa.”[11]
Although “histones were retained in sperm without affecting its ability to fertilize,” this process of histone removal and replacement with protamine was required because “at fertilization, male chromosomes were aberrantly recognized by maternal factors that control female meiotic progression, leading to a deleterious premature division and early loss of male chromosomes.” In other words, this entire process was another example of irreducible complexity. It highlights the role of sperm chromatin in protecting male chromosomes in the egg. The details of the process of histone removal include the effects of
mutant paternal loss (pal), sperm chromatin retains germline histones H3 and H4 genome wide without impairing sperm viability. However, after fertilization, pal sperm chromosomes are targeted by the egg chromosomal passenger complex and engage into a catastrophic premature division in synchrony with female meiosis II. … pal encodes a ….protein specifically required for the eviction of (H3-H4)2 tetramers from spermatid DNA after the removal of H2A-H2B dimers. Our study thus reveals an unsuspected role of histone eviction from insect sperm chromatin: safeguarding the integrity of the male pronucleus during female meiosis.[12]
Epigenetic Roles
Furthermore, we now know that “specialized sperm DNA packaging also confers a vital, post-fertilization function… the epigenetic identification of paternal chromosomes as distinct from maternal chromosomes. Without this epigenetic distinction, the paternal DNA shatters before the first zygotic division.”[13] One result of this major compaction step is biological competency is lost. Consequently, biological competency must be restored to sperm. This requires reestablishing paternal DNA packaging.
Summary
This entire line of research on sperm illustrates the fact that even small changes in the design of sperm can have catastrophic effects on the ability of sperm to function and birth the next generation. And sperm could not function for reproduction until the design outlined above was established and functional. This again documents the fact that the sperm design is not only complex but irreducibly complex. It also presents another reason why sperm could never have evolved from some asexual reproductive system.
See Dr Bergman’s previous posts in this series:
- Part I: Intricate Design Found in Sperm Cells (15 Nov 2023).
- Part II: More Details on Sperm Design Published (22 Nov 2023).
References
[1] Fisher, Heidi, et al. “On the Origin and Evolution of Sperm Cells.” Cells 12(1):159, January 2023.
[2] Fisher, et al., 2023.
[3] Simmons, L.W., and N. Wedell. “Fifty years of sperm competition: The structure of a scientific revolution.” Philosophical Transactions of the Royal Society. B Biological Science. 375: 20200060, 19 October 2020.
[4] Smith, F. LaGard. Darwin’s Secret Sex Problem: Exposing Evolution’s Fatal Flaw–The Origin of Sex. WestBow Division of Thomas Nelson and Zondervan, Bloomington, IN, 2018.
Bergman, Jerry. 2022. The Three Pillars of Evolution Demolished.
Westbow Press: Bloomington, IN (a division of Thomas Nelson & Zondervan).
[5] Fisher, et al., 2023, p. 2.
[6] Fisher, et al., 2023, p. 2.
[7] Bergman, Jerry. The Three Pillars of Evolution Demolished: Why Darwin Was Wrong. WestBow Division of Thomas Nelson and Zondervan, Bloomington, IN, 2022.
[8] Lopez, Bianca, et al. “Unequal impacts.” Science 382(6671):659-661, 2023.
[9] Dubruille, Raphaëlle, et al. “Histone removal in sperm protects paternal chromosomes from premature division at fertilization.” Science 328(6671):725-731 10 November 2023.
[10] Dubruille, et al., 2023.
[11] Akmal, Muslim, et al. 2016. “The important role of protamine in spermatogenesis and quality of sperm: A mini review.” Asian Pacific Journal of Reproduction 5(5):357-360, September 2016.
[12] Dubruille, et al., 2023.
[13] Levine, Mia. “A case of mistaken epigenetic identity. The specialized packaging of sperm DNA preserves genome stability in the fruit fly zygote” Science 382(6671):643-644, https://www.science.org/doi/full/10.1126/science.adl0365, 9 November 2023.
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 1,800 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.