April 1, 2021

Download PDF

This article was originally published as a chapter in the book “Design and Catastrophe: 51 Scientists Explore Evidence in Nature"

The specialized fields of taxonomy and systematics currently hold the theory of evolution as an essential dogma. This is in marked contrast to the thinking of many early naturalists who did not hold a naturalistic view of the origin of life. The founder of modern taxonomy, Carolus Linnaeus (Carl Linnaeus or Carl von Linné) wrote in the preface to one of his latter works: “The Earth’s creation is the glory of God, as seen from the works of Nature by Man alone.”[1] In his view, the study of nature would reveal the order of God’s creation. It would be good to be free to explore scientific enquiry with similar sentiments, and it is with these sentiments and the postulate that nature is designed to survive environmental disturbance by adapting to stress that this chapter is written. This order in nature can be seen in three specific processes: genetic recombination, epigenetic effects, and gene mutations.

Through the processes of genetic recombination (crossing over), epigenetic effects (DNA methylation and histone modification), and gene mutations, species can possess significant diversity. This diversity is necessary for the genetic health of any population, often mitigating the effects of genetic bottlenecking and reducing the threat of species extinctions, which are preceded by a loss of genetic diversity within species caused by sharp reduction in population sizes due to environmental stress.[2] Individuals of the same species may exhibit differences in the expression of the same genes (phenotypic plasticity). Both genetic diversity and phenotypic plasticity[3] are drivers in the process of speciation leading to the species biodiversity we see today.

In most sexually reproducing organisms, offspring are never genetically the same except for monozygotic multiples. This variation in the genes inherited is produced by the meiotic cell cycle. Unlike the mitotic cell cycle, which occurs in somatic cells and produces two cells identical to the original parent cell, meiosis only occurs in reproductive cells and produces four cells that contain a different genetic composition from each other and possess only half of the genetic material of the original cell. This diversity in genetic composition arises during a phase of meiosis in which chromosomes can temporarily overlap and fuse their arms, causing a crossover or recombination of genetic material. It is here that diversity in sexual reproducing organisms is initiated. Several other factors also influence genetic diversity; however, these factors are secondary. Recombination should be viewed as the initiation of genetic diversity among individual offspring of sexually reproducing organisms.

DNA methylation occurs when methyl groups are added to the DNA molecule. This changes the activity of that segment of DNA without changing the DNA sequence itself. Histone modifications affect the structure of the proteins (histones) that package DNA, and this affects gene expression. Environmental stimuli, or stress, promote epigenetic changes that, in turn, generate differences in the expression of DNA sequences;[4] this leads to changes in the heritable characters across generations. These changes are often expressed as increased stress tolerance and destabilized genomes (genetic diversity). Epigenetic regulations are the source of these changes, and their effects can be seen as early as in the immediate offspring and may persist beyond the ensuing generation,[5] but are not permanent and often persist as long as the population is exposed to the causative environmental stress. This plasticity in the expression of a genetic code (phenotypic plasticity) is essential for the adaptability and survival of populations.

Genetic mutations are permanent modifications to the DNA sequence of an organism and are often viewed as errors as they most often adversely affect an organism’s survival. Mutations that are not the cause of diseases or other deleterious effects may be neutral (of no effect) or offer increased survivability to the individual, population, or species in which it occurs. While it is generally accepted that the majority of mutations are either neutral or deleterious, the ones that are beneficial are often of significant importance to the survival of organisms, population, and species. Mutations, therefore, can be viewed as a genetic lottery system in which the survivability of the species, not the individual, is increased over time as its random mutations are exposed to non-random selection processes. This is a deliberate design to allow species to increase genetic diversity over time.

In whatever cells gene mutations occur and whatever the results of genetic recombination are, the expression of these genes is environmentally modulated through epigenetic influences. We can view genetic recombination as designed to affect the survivability of the individual. Epigenetic effects on genes that result in differences in the expressions of those genes (phenotypic plasticity) may be viewed as having been designed to affect the ensuing generations or populations exposed to a catastrophe. Random gene mutations and the nonrandom selection processes that act on them may be designed to affect the survivability of a species over time for the long term. These processes are specifically designed to enable, respectively, individuals, populations, and species to survive in an ever-changing environment and to adapt to catastrophic events, be they a global flood, volcanic eruption, drought, severe heat, extreme cold, or another environmental stress.

NOTES

[1] K Dorst, K van Overveld. Typologies of Design Practice. In: Meijers AWM, editor. Philosophy of technology and engineering sciences, Amsterdam (The Netherlands): Elsevier 2009; p. 457.

[2] R Frankham. Genetics and extinction. Biological Conservation 2005; 126(2):131–140.

[3] CD Schlichting. The role of phenotypic plasticity in diversification. In: DeWitt TJ, Scheiner SM, editors. Phenotypic plasticity: functional and conceptual approaches, Oxford (UK): Oxford University Press; 2004, pp. 191–200; AP Moc-zek. Phenotypic plasticity and diversity in insects. Philosophical Transactions of the Royal Society B–Biological Sciences 2010; 365(1540):593–603.

[4] A Varriale. DNA methylation, epigenetics, and evolution in vertebrates: facts and challenges. International Journal of Evolutionary Biology 2014; Article ID 475981.

[5] A Boyko, I Kovalchuk. Genome instability and epigenetic modification— heritable responses to environmental stress? Current opinion in plant biology 2011; 14(3):260–266.

Delano S. Lewis is an associate professor at Burman University and holds a PhD degree in Entomology from the University of Florida. He is an insect systematist who specializes in Lepidoptera (moth/butterfly) taxonomy, systematics, phylogenetics, and diversity. He publishes mainly on insects but has published on Jamaican Iguanas, Indian Mongoose, and a possible biorational pesticide, among other things.