A roadside weed plants a seed of evolutionary doubt
Nonrandom mutations threaten Darwinian orthodoxy
It may be a common roadside weed, but the DNA of the thale cress may present a challenge to a key part of neo-Darwinian evolutionary theory. A study published in the Feb. 3 issue of the scientific journal Nature says that genetic mutations of the weed—that is, changes in its DNA over time—were not as random as scientists had expected.
That much everyone agrees on. Where they don’t agree is how to interpret those findings.
Researchers at the University of California, Davis, and the Max Planck Institute for Biology in Germany spent three years sequencing the DNA of thousands of specimens of thale cress, a species known as a “lab rat” for plant scientists. The study’s authors had predicted all sections of the plant’s DNA would have an equal chance at mutating. Instead, they found some sections of the DNA mutated more often than others. The sections controlling essential functions of the plant were least likely to mutate.
This “mutation bias” is a good thing for the thale cress. It’s also good for humans, who appear to benefit from the same phenomenon: A separate study published in Genome Research in January found that people in Africa, where malaria is common, were more likely than Europeans to develop a de novo genetic mutation (one not inherited from either parent) protecting them from the disease. Lead author Adi Livnat from the University of Haifa told Salon the results “challenge the central neo-Darwinian assumption on a fundamental level.”
Everyone from farmers to animal breeders to cancer researchers stands to benefit from this new knowledge of mutation bias. But it may prove troublesome for evolutionary theory, which has long asserted that genetic mutations are completely random. According to neo-Darwinism, when an organism breeds, the new DNA that results is as random as a roll of the dice. Those with weak, inferior gene combinations breed less and die out over time, while winners advance the species.
But if DNA mutations aren’t random after all, where does this leave the theory of evolution and natural selection?
Grey Monroe, the lead author of the thale cress paper and an assistant professor in the UC Davis Department of Plant Sciences, defends a Darwinian explanation. He told me his study’s results “really highlight the power of natural selection to shape even the mutation process itself.”
Monroe uses the analogy of “loaded dice” in the paper to explain how natural selection chooses which genes to mutate. Essential genes would be less likely to get bad rolls and spared from potentially harmful mutations, while all other genes would have about the same odds.
However, others say biological processes described as “nonrandom” point to an intelligent creator.
Casey Luskin, a scientist and associate director for the Center for Science and Culture at the Discovery Institute, said “the implications for evolutionary biology are profound” and fly in the face of Darwinism.
“If mutations aren’t equally distributed across the genome and aren’t random with respect to the needs of the organism, then two basic tenets of the standard neo-Darwinian model of evolution are false,” he said via email.
Luskin added that the study’s discovery of mutation bias presents another problem for evolution. If the essential sections of an organism’s DNA mutate less, the species would take longer to evolve than today’s fossil records suggest. That presents a “waiting time” problem that many evolutionists have not readily admitted or reconciled, Luskin said.
Creation Research Society board member Jean Lightner also sees the problem for neo-Darwinism.
“This talk of nonrandom and mutation bias screams design to me,” she said. “There’s always talk of something ‘arising out of natural selection’ but natural selection can’t make anything new.”
Neither Luskin nor Lightner believe the new findings will change the minds of people firmly committed to the evolutionary paradigm. But for now at least, the Nature study has gotten people thinking.
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