Do Genome Sizes Prove Evolution?
Simple life-forms have small, simple genomes.
Complex life-forms have large, complex genomes.
Does this prove evolution?
Genome sizes should correlate with phylogeny. At least this is what evolutionists have predicted, but this is not what genetic analysis has actually found. The problem for evolution is the enormous number of exceptions to the rule, “simple life, simple genome.” Some “primitive, simple” organisms have larger genomes than some complex organisms thought to be highly evolved. One recent sequence analysis of a creature that has the largest known animal genome is not the most-evolved animal, but one of the supposedly least-evolved animals. It is not a reptile, bird, or mammal, but rather a primitive fish called a lungfish that looks like a worm!
Figure 1. The South American lungfish. From Universitӓt (University of) Konstanz, “Decoding the world’s largest animal genome.” 14 Aug 2024.
A lab sequence of the creature, a South American lungfish (Lepidosiren paradoxa) determined it has a genome that is about 91 gigabytes, a storage capacity that is roughly equivalent to one billion bytes. This is roughly 30 times the size of the human genome! It “is the largest animal genome sequenced so far and more than twice the size of the Australian (Neoceratodus forsteri) and African lungfish,” noted M. Schart in a new report in Nature.[1]
Its genome is not simply larger than ours, but is an amazing 30 times larger.[2] Because “these ancient living fossils” still look very much like their early ancestors, evolutionists assume the lungfish genome is very similar to its very early ancestor.[3] Likewise, the genomes of many so-called “simple” life-forms are far more complex than the size long predicted by evolutionists (see Figure 4).
Reasons for Genome Size Diversity
One explanation for the enormous genome size of the lungfish could be related to several enlarged intergenic regions due to highly repeated introns, which are spliced out of genes when they are transcribed. These regions would therefore be expanding because certain transposable elements are still active today, resulting in multiple copies of themselves. Transposable elements, also known as “jumping genes,” are DNA sequences that are able to move from one location on the genome to another location.
Over the next several decades, it has became apparent that not only do transposable elements “jump,” around the genome, but they are also found typically in large numbers in almost all organisms, both prokaryotes and eukaryotes. For example, one source claims that transposable elements make up approximately 50 percent of the human genome and up to 90 percent of the maize genome. This was also the explanation given for the existence of South American lungfish genome size which turned out to be 30 times larger than the human genome.[4]
Claims that introns and transposons are “useless” are analogous to the vestigial organs argument used by evolutionists. My suspicion is that functions will be found for most, if not all, of the non-coding DNA. One point is, if they were really mutated junk, why would the body continue to replicate and maintain them?
As was determined for the so-called vestigial organs, there may be a functional reason for the large number of DNA repeats in the lungfish genome. Professor Schart mentions one possible reason, specifically that transposable element abundance facilitates chromosomal rearrangements, which may aid in environmental adaptation.[5]
Table 1. According to this diagram, protein-coding genes and the total number of genes closely correlate with evolutionary progress; T. aestivum, common wheat grass, is the major exception. Other comparisons of these organisms tell a very different story. Another problem is some of the numbers cited in the table above are only estimates. Furthermore, geneticists have sequenced only a small percent of the estimated several million existing life-forms.
Figure 2. Valid genomic comparisons also require comparisons of specific genetic components as shown in the chart above. Note this chart shows transposable elements within the human genome are only about 11 percent in contrast to 50 percent in the lungfish genome. This illustrates how tenuous some of these estimates are. This chart is based on the International Human Genome Sequencing Consortium’s “Initial sequencing and analysis of the human genome,” Nature 409:860-921, p. 860, 2001.
Figure 3. When specific genes are evaluated, very different results are produced compared to when the total genome size is evaluated; in this case, the olfactory receptor genes of those primates that were listed are at the lower end of the scale. Evidence exists that most or at least many pseudogenes have a function, even when comparing documented functional genes. Elephants have twice as many olfactory receptor genes as dogs and five times as many as humans. From Graduate School of Agricultural and Life Sciences, The University of Tokyo, “Elephants have twice as many olfactory receptor genes as dogs—Genome comparison reveals mammalian diversity,” 12 August 2014.
Figure 4. An example of two very “simple” life-forms (Daphnia, commonly known as water fleas, and rice) at the base of the evolutionary tree, both of which have many more genes than humans. This illustrates the fact that the number of genes in an organism is not a valid indicator of biological complexity.
Schart research supports the conclusion that mutations cause genetic deterioration
One finding of the Schart study, which supports the creationists’ conclusion that mutations in general move the genome toward deterioration, was an analysis of the parasitic bacterium Mycoplasma mycoides. This organism has one of the smallest genomes known in any life-form. The genome consists of a single circular chromosome containing only 985 claimed genes with a size of 1,211,703 base pairs and a G+C-content which is the smallest among all genomes thus far sequenced. As a parasite, to survive it must live, and feed, on another organism, and thus does not possess the genes required to subsist on its own.
The analysis of the M. mycoides genome concluded that one specific genetic code mutation was 30 times more likely to switch an A or a T to a G or a C than the other way around. In the minimalist cell, this mutation was 100 times more likely. Minimalist cells are cells in which genes are removed down to their most basic fundamentals and still live, namely a life-form with the smallest genome possible that still allows it to grow and divide in the lab.[6]
This mutation results in fewer and fewer A-T bases and a rapid increase in the number of G-C bases. The end-result is a loss of a functional code and a gain of a non-functional, mutated code. The four DNA bases that make up the universal DNA code are the T (Thymine) and A (Adenine) pairing, and the G (Guanine) and C (Cytosine) pairing. This mutation illustrated with English words given the following meaningful sentence, “the top award was to a cute rabbit with a raccoon tail,” becomes “ahe aop twtrd wts to t guae rtbbt wiaa t rtggoon atil,” which is completely nonsensical. This example illustrates the total loss of meaning due to this mutation type. The same is true with the DNA code.
Summary
The large number of exceptions illustrates the fact that the naive, evolutionary conclusion that “simple” life-forms have small, simple genomes, and complex life-forms have large, complex genomes, is erroneous. Many very “simple” life-forms have genomes much larger than some life-forms that evolutionists regard as being the most-evolved life-forms, such as humans. Why this exists is unknown, but some plausible theories have been proposed, such as the expansion of transposable elements and the possibility that the abundance of transposable elements facilitates chromosomal rearrangements. Nonetheless, regardless of the reason, both the size and complexity of the genome often do not conform to the traditional, evolutionary expectation. This generality currently holds and will hold until more genomes are sequenced.
References
[1] Schart, M., et al., ”The genomes of all lungfish inform on genome expansion and tetrapod evolution,” Nature 3901(9684), https://doi.org/10.1038/s41586-024-07830-1, 2024.
[2] Schart, et al., 2024.
[3] Universitӓt Konstanz, “Decoding the world’s largest animal genome,” https://www.uni-konstanz.de/en/university/news-and-media/current-announcements/news-in-detail/das-groesste-genom-aller-tiere-entschluesselt/, 14 August 2024.
[4] Schart, et al., 2024.
[5] Schart, et al., 2024.
[6] Westberg, J.,“The genome sequence of Mycoplasma mycoides subsp. mycoides SC type strain PG1T, the causative agent of contagious bovine pleuropneumonia (CBPP),” Genome Research14(2):221–227, February 2024.
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 1,900 publications in 14 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.