Is Junk DNA Making a Comeback?

Evolutionists irritated by ENCODE mount a counterattack, claiming that the majority of human genes are evolutionary leftovers with no function.

From 20% junk to 75% junk in only a few years: Why one should be skeptical about even hard science

by Dr Jerry Bergman

A new study claims that 90 to 75 percent of the genome is junk DNA, and that no more than 25 percent of the human genome is functional. In contrast, in 2012 the Encyclopedia of DNA Elements (ENCODE) project that involved 21 leading international scientists concluded that as much as 80 percent of the genome is functional.[i]

A study published in Genome Biology and Evolution Journal, by Dan Graur and Rebecca Moores, Professor of Biology and Biochemistry at University of Houston, attempted to determine how much of the genome is functional.[ii] To do this, they compared the deleterious mutation rate and the replacement fertility rates. The problem they identified is the mutation rate has been empirically determined to be close to 2 × 10^-8 mutations per nucleotide per generation.

Given 3 billion DNA pairs, [2 x 10^-8] x [3 x 10⁹] would amount to 60 new mutations introduced for each baby born. This compares with other estimates of around 70 new mutations for each baby born. If each child has about 70 new mutations compared to his or her parents, and this child’s children each have an additional 70 new mutations, the mutation number, especially in humans, will accumulate, eventually leading to mutational meltdown and extinction:

Each of us is born with about 70 new genetic errors that our parents did not have. That’s much more than a slime mold, say, or a bacterium. Mutations are likely to decrease an organism’s fitness, and an avalanche like this every generation could be deadly to our species.[iii]

Given that genome size and the rate of deleterious mutations in the functional parts of the genome, Graur developed a model to calculate the decrease in reproductive success induced by harmful mutations, known as the “mutational load,” in relation to the portion of the genome that is functional.

The functional portion of the genome includes protein-coding genes, RNA-specifying genes and DNA receptors. In his model, mutations in the nonfunctional portions are neutral since damage to functionless parts by definition will not adversely affect health. Because of deleterious mutations, each couple in each generation today must produce close to 2.1 children to maintain a constant population. Over the past 200,000 years, replacement-level fertility rates have ranged from 2.1 to 3.0 children per couple. Global population has remained remarkably stable until the beginning of the 19th century, when decreased mortality in newborns resulted in fertility rates exceeding replacement levels. Graur explained that

For 80 percent of the human genome to be functional, each couple in the world would have to beget on average 15 children and all but two would have to die or fail to reproduce. If we use the upper bound for the deleterious mutation rate (2 × 10^-8 mutations per nucleotide per generation), then … the number of children that each couple would have to have to maintain a constant population size would exceed the number of stars in the visible universe by ten orders of magnitude.[iv]

In short, he concluded that 80 percent of the genome could not be functional because if that were so, humans would have been extinct long ago.

[i] An Integrated Encyclopedia of DNA Elements in the Human Genome. Nature. 2012 Sep 6; 489(7414): 57–74.

[ii] Dan Graur. An upper limit on the functional fraction of the human genome. Genome Biology and Evolution, 2017; DOI: 10.1093/gbe/evx121.

[iii] Greenwood, 2017.

[iv] Jeannie Kever. 2017. New limits to functional portion of human genome reported; Work suggests at least 75 percent of the genome is junk DNA. Science Daily, https://www.sciencedaily.com/releases/2017/07/170714140234.htm

Two problems with his conclusion are his deep time assumption based on Darwinism, and the assumption that the mutation rate observed today was the same rate in the past. A creationist worldview would place the first humans at 6,000 years ago, and the mutation load of the first humans at zero. From this foundation, even at the current level of 20 percent useless DNA, and the added number of 60 new mutations per generation is reasonable, and fits the facts far better than the Darwinian deep-time model.

See John Sanford’s book Genetic Entropy for more on mutational load and reasons why this shows the human genome cannot be millions of years old.

Dr Jerry Bergman, professor, author and speaker, is a frequent contributor to Creation-Evolution Headlines. See his Author Profile for his previous articles.