Evolution: a different view with loss of traits; not Behe (Introduction)

by David Turell , Tuesday, September 01, 2020, 17:29 (1543 days ago) @ David Turell

Another article:

https://www.quantamagazine.org/by-losing-genes-life-often-evolved-more-complexity-20200...

"Two surprising analyses that appeared in Nature Ecology & Evolution early this year have hammered home just how inessential genes can be, and how creatively evolution can deal with losing them. By analyzing hundreds of genomes from across the animal kingdom, researchers in Spain and the United Kingdom showed that a startling degree of gene loss pervades the tree of life.

"Their results suggest that even early animals had relatively complex genomes because of an unprecedented spurt of gene duplication early in life’s history. Later, as lineages of animals evolved into different phyla with distinct body plans, many of their genes began to disappear, and gene loss continued to be a major factor in evolution thereafter. In fact, the loss of genes seems to have helped many groups of organisms split away from their ancestors and triumph over new environmental challenges.

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"In a recent study that looked at different forms of genes in Arabidopsis plants from all over the globe, researchers in China and California found that about 66% of protein-coding genes had broken versions, known as loss-of-function variants. Surprisingly, 1% of these less functional genes were under positive evolutionary selection — that is, the plants with the missing or broken genes thrived better than those with working versions. These results validate the intriguing idea, proposed by the genetics researcher Maynard Olson of the University of Washington back in 1999, that “less is more”: Sometimes, losing a gene can be adaptive.

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"One of the best examples of adaptive gene loss in animals can be seen in cetaceans (the order of aquatic mammals including whales and dolphins), which have lost 85 protein-coding genes seen in other mammals, as Hiller reported last year. Many of these losses are probably neutral, but some seem linked to diving-related adaptations, like the narrowing of blood vessels during diving. One of the lost genes, KLK8, is interesting because it is involved in the development both of sweat glands in the skin and of the hippocampus in the brain; cetaceans lost it during their transition from land back to water. The loss of this gene is linked to the development of a thicker epidermis and the loss of hair (hair is not adaptive in aquatic environments, where it creates drag and does not preserve body heat as it does in terrestrial animals).

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"Yeasts are not alone in their metabolic virtuosity. Dolphins and whales, Old World fruit bats, and elephants — three lineages with relatively big brains — have all lost a gene, HMGCS2, required for ketogenesis, a metabolic process that scientists had thought was required to support the activity and growth of large, energy-hungry brains. Brain cells consume glucose, but when that is unavailable, they fuel themselves with ketone bodies from fatty acids. HGMCS2, the enzyme that converts fatty acids into ketone bodies, becomes especially important during fasting.

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"How elephants and cetaceans feed their hungry brains without ketogenesis is still unknown, but they seem to have evolved alternative ways to address the physiological challenge. “You wouldn’t have known this is an exceptional lineage without having observed that this key gene is lost,” Hiller said.

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"More generally, the pervasiveness of gene loss in the tree of life points to an inversion of a classic theme in evolutionary developmental biology. In the 1970s and ’80s, “the big shock was to find that flies and humans use the same genes,” Cañestro said. Replace the fly Pax6 gene with the human version, and the fly can still make an eye. “Now we are finding that sometimes the structures [that grow] are the same, but the genes responsible for making the structures have many differences,” he said. “How is it possible that there are so many different genes, and still the structures are the same? That’s the inverse paradox of evo-devo.'”

Comment: Behe is supported without his being mentioned. Obviously the original DNA was designed to have multiple parallel backup systems of genes, so DNA could devolve as Behe states. Considering my error theory: if God made original DNA complete and perfect there is no need for Him to edit changes except to be sure the deletions are correct.