Sexual Reproduction: A Continuing Mystery to Evolutionists
by Rich Deem

It is apparent from the fossil record that asexual reproduction was the first form by which living organisms reproduced on the early earth. Many simple organisms, such as bacteria, and simple animals, such as protists and worms still reproduce asexually, but sexual reproduction is, by far, the most widely used method by which species maintain their presence on our planet. The evolutionist is faced with the problem of how sexual reproduction arose in the first place and how it is maintained given the obvious advantages of asexual reproduction. Scientific explanations that could account for the maintenance of sexual reproduction in some species usually have no influence on asexual organisms from which their sexual descendents were supposed to have evolved. Therefore, multiple mechanisms are required to explain the origin and maintenance of sexual reproduction.

There are some basic problems concerning sexual reproduction that are still a puzzle to evolutionists and are very difficult to explain using any evolutionary models. In all sexually reproducing species, the genetic material ( Deoxyribonucleic acid: the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms.DNA) that codes for the organism's design is stored in a pair of Threadlike "packages" of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and two sex chromosomes. Each parent contributes one chromosome to each pair, so children get half of their chromosomes from their mothers and half from their fathers.chromosomes. The process of sexual reproduction involves the formation of gametes (eggs and sperm) that involves the halving of chromosomal pairs. The subsequent recombination of gametes (and Threadlike "packages" of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and two sex chromosomes. Each parent contributes one chromosome to each pair, so children get half of their chromosomes from their mothers and half from their fathers.chromosomes) from different individuals is much more likely to break up combinations of good Functional and physical units of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.genesthan to form them. In effect, sexual reproduction dilutes Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations (both good and bad) so that they are usually not expressed in the offspring. This fact is an obvious problem for evolutionary theories that require the expression of Functional and physical units of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.genesin order for natural selection to operate.

Evolutionists have traditionally explained the existence of sexual reproduction as a means to promote genetic variability and, therefore, increase the rate of evolution. However, this explanation suffers from several problems.1 There is no consistent experimental proof that sexual reproduction promotes genetic variability. In addition, recombination breaks up favorable sets of Functional and physical units of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.genes that have accumulated through selection. This fact alone "should cause sex and genetic recombination to be eliminated from a population at equilibrium under selection alone."1 A third problem is the "cost" of sexual reproduction. The production of males is a "cost" that lowers the fitness of species in a competitive world. In many species, the males does nothing for the species other than providing sperm. For example, the male lion does not hunt for food or take any part in the rearing of young. However, males must be fed by the females, which uses up half of their food resources with no benefit produced in return. The male lion reduces the "fitness" of the species by two-fold. Here is another example of how sexual reproduction costs a species. Let us say that there are a million members of a species of sexually reproducing snails. At some point, there arises one female that is able to reproduce asexually. This female produces two females while her sexual cousins produce one male and one female. Therefore, for each generation, the asexual snails produce twice as many reproducing members as the sexually reproducing species. According to population dynamics, the asexual mutants would completely replace the original population within 52 generations.2 Despite the increased cost of sexual reproduction, it persists over asexual reproduction.

"I emphasize experimental problems, because we have tons of theories, and some are completely crazy."

Alexey Kondrashov, Cornell University

Given these problems, what theories do evolutionists propose for the presence of sexual reproduction? Most fall into two categories: 1) sexual recombination brings beneficial Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations together so that they can be expressed in the population and 2) sexual reproduction purges the All the DNA contained in an organism or a cell, which includes both the chromosomes within the nucleus and the DNA in mitochondria.genome of harmful Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations. However, most of these theories are without experimental support. According to evolutionary geneticist, Alexey Kondrashov (Cornell University), "I emphasize experimental problems, because we have tons of theories, and some are completely crazy."2

One theory states that sexual reproduction facilitates mechanisms for repair and chromosomal segregation. However, recombination is not essential for repair of Deoxyribonucleic acid: the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms.DNA, except for double-stranded breaks. Given that double-stranded breaks in the Deoxyribonucleic acid: the chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms.DNA are formed as a function of meiosis, it would seem odd that meiotic recombination would repair them.3 According to Dr. Brian Charlesworth, "evolutionary degeneration of One of the two sex chromosomes that determines maleness in mammals, carried and passed down from males to males.Y Chromosomes, which are sheltered from recombination, demonstrates that genetic recombination is necessary to preserve the long-term fitness of a large All the DNA contained in an organism or a cell, which includes both the chromosomes within the nucleus and the DNA in mitochondria.genome."4 However, Dr. Charlesworth seemed oblivious to the obvious problem of how evolution could proceed given that the One of the two sex chromosomes that determines maleness in mammals, carried and passed down from males to males.Y chromosome degenerates, although it must be passed down to the next and following generations (actually, for hundreds of millions of years, according to evolutionary theories).

Another theory states that variation maintained by genetic recombination increases the survival of offspring by reducing competition between individuals. However, competition between siblings is limited to certain species. Obviously, this explanation cannot account for the pervasiveness of sexual reproduction in species in which individual competition does not occur.1

With these theories eliminated as possible explanations for the existence of sexual reproduction, evolutionists have proposed that non-random associations and interactions between Functional and physical units of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.genes affect the fitness of populations. The evolutionist must eliminate effects within a genetic The place on a chromosome where a specific gene is located, a kind of address for the gene.locus (location) because such effects are unimportant in asexual organisms. Although such effects might explain the persistence of sexual reproduction, they would fail to account for the reason that sexual reproduction would ever evolve in the first place. Selection might act to favor associations of certain The functional and physical unit of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.gene combinations, but recombination acts to randomly shuffle the deck to break up these favorable combinations. However, if different The functional and physical unit of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.gene combinations are important in different generations, recombination would be advantageous because it would reshuffle the combinations in subsequent generations. However, the relevant parameters must be delicately adjusted for this mechanism to work, and is, therefore, unlikely to be of general importance.5

Another potential theory for the prevalence of sexual reproduction is the interaction of hosts and parasites. However, evidence for the validity of this argument is weak, and most likely represents effects on One of the variant forms of a gene at a particular locus, or location, on a chromosome.allele frequencies. Variant forms of a gene at a particular locus, or location, on a chromosome.Alleles are different versions of a genes that may be found in an individual - for example, the Functional and physical units of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.genes that control eye color. My wife has green eyes and I have brown eyes, although my father has green eyes so that I have A genetic disorder that appears only in patients who have received two copies of a mutant gene, one from each parent.recessive Variant forms of a gene at a particular locus, or location, on a chromosome.allelesfor light eye color. One of our children has blue eyes, one gray eyes and the last brown eyes). In order for this mechanism to be valid, it would be expected that rare genetic combinations would be less infected/parasitized than more common genetic combinations. Studies have shown that this is often not the case.6

"Critical tests to discriminate between alternative theories have been hard to devise."

Barton, N.H. and B. Charlesworth1

In conclusion, the mechanism by which sexual reproduction could have arisen evolutionarily has not been addressed to any significant degree. The 2-fold "cost" associated with sexual reproduction makes it extremely unlikely that it could have arisen naturalistically. There have been many theories proposed to explain the perpetuation of sexual reproduction. None of these theories can account for the maintenance of sexual reproduction in all cases. The one thing that is clear from scientific studies is that sexual reproduction and recombination function to dilute Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations. The vast majority of these Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations are neutral (neither beneficial nor harmful). Of the remainder, most are detrimental. By diluting these detrimental Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations, nearly all of the individuals within a species remain unaffected (since each person has two copies of each One of the threadlike "packages" of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and two sex chromosomes. Each parent contributes one chromosome to each pair, so children get half of their chromosomes from their mothers and half from their fathers.chromosome, the "good" copy allows for normal function of the gene). However, not only does recombination dilute harmful Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations, but also beneficial Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations. Since the beneficial Permanent structural alterations in DNA, consisting of either substitutions, insertions or deletions of nucleotide bases.mutations are usually not expressed, selection cannot act on them and evolution cannot proceed.

The theoretical nature of these principles were recently demonstrated to be true in a just-completed 35 year study of an isolated population.7, 8 The recent study destroys the idea that isolated groups of a population go on to evolve into a new species. Instead of becoming a new species, populations that suffer drastic reductions in numbers are characterized by decreased genetic variability and an expression of detrimental Functional and physical units of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.genes. This happens because normally Possessing two different forms of a particular gene, one inherited from each parent.heterozygous (containing 2 different Variant forms of a gene at a particular locus, or location, on a chromosome.alleles of each gene) individuals become Possessing two identical forms of a particular gene, one inherited from each parent.homozygous, due to inbreeding. As a result, detrimental, non-expressed, A genetic disorder that appears only in patients who have received two copies of a mutant gene, one from each parent.recessive Functional and physical units of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.genes become Possessing two identical forms of a particular gene, one inherited from each parent.homozygous and, therefore, are expressed, resulting in a less fit population. The study examined the effect of a 35-year population decline of an isolated group of greater prairie chickens on their fitness and fertility. The results showed that population decline and isolation of the prairie chicken led to decreased genetic variability, reduced egg viability (from near 100% to less than 80%), and a decline of fertility rates (from 93% to 74%).8 Only after human intervention (which brought in genetically diverse individuals from other areas) did the population begin to recover. This study confirms what we see in the fossil record that species remain unchanged until they do extinct. Even evolutionists are now recognizing this fact:

"Eldredge and Gould not only showed that paleontologists had been out-of-step with biologists for decades, but also that they had unconsciously trying to force the fossil record into the gradualistic mode. The few supposed examples of gradual evolution were featured in the journals and textbooks, but paleontologists had long been mum about their ‘dirty little trade secret:' most species appear suddenly in the fossil record and show no appreciable change for millions of years until their extinction."9

The lack of success of evolutionary models for sexual reproduction is not surprising for those who accept a Creator God. We believe God created species with a limited ability to change in response to changing conditions. When species went extinct, God replaced them with new species. Sexual reproduction and recombination are part of God's plan, since they limit the expression of mutated Functional and physical units of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.genes that would have had detrimental effects upon the individual who possessed the The functional and physical unit of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.gene. In addition, God created humans as males and females for the expressed purpose of marriage10 and unity within the body of Christ,11 as fellow servants and heirs in Him.12


References Top of page

  1. Barton, N.H. and B. Charlesworth. 1998. Why sex and recombination? Science 281: 1986-1990.
  2. Wuethrich, B. 1998. Why sex? Putting theory to the test. Science 281: 1980-1983.
  3. Klechner, N. 1996. Proc. Natl. Acad. Sci. U.S.A. 93: 8167.
  4. Charlesworth, B. 1996. Curr. Biol. 6: 149.
  5. Otto, S.P. and Y. Michalakis. 1998. Trends Ecol. Evol. 13: 145.
  6. Dybdahl, M.F. and C.M. Lively. 1995. Proc. R. Soc. London Ser. B 260: 99.
  7. Soulé, M.E. and L.S. Mills. 1998. No need to isolate genetics. Science 282: 1658.
  8. Wetermeirer, R.L., J.D. Brawn, S.A. Simpson, T.L. Esker, R.W. Jansen, J.W. Walk, E.L. Kershner, J.L. Bouzat, and K.N. Paige. 1998. Tracking the long-term decline and recovery of an isolated population. Science 282: 1695.
  9. Prothero, D.R. 1992. Punctuated Equilibrium At Twenty: A Paleontological Perspective. Skeptic 1: 38-47.
  10. For this reason a man will leave his father and mother and be united to his wife, and they will become one flesh. (Genesis 2:24).
    However, in the Lord, neither is woman independent of man, nor is man independent of woman. (1 Corinthians 11:11)
    See also Matthew 19:4-5
  11. There is neither Jew nor Greek, there is neither slave nor free man, there is neither male nor female; for you are all one in Christ Jesus. (Galatians 3:28)
  12. The Spirit Himself bears witness with our spirit that we are children of God, and if children, heirs also, heirs of God and fellow heirs with Christ, if indeed we suffer with Him in order that we may also be glorified with Him. (Romans 8:16-17)

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Last Modified September 21, 2002

 

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