From ‘Heretic’…

From Chapter 9 of Heretic
Here’s the section Rossiter refers to, from Chapter 9 of Heretic: The most impressive evolutionary experiment to my knowledge so far reported was carried out by an international team using Salmonella enterica. On October 22, 2012 a report claimed that this was the first time a group demonstrated the origin of a new gene.

In reality a gene with a weak side-activity was duplicated and the side-activity was strengthened. Intriguing, but nothing more — and nothing new. Yet what follows is how the work was described in the popular press (emphasis added to show where intelligent engineering was introduced into the experimental environment): “Researchers engineered a gene that governed the synthesis of the amino acid histidine, and also made some minor contributions to synthesizing another amino acid, tryptophan. They then placed multiple copies of the gene in Salmonella bacteria that did not have the normal gene for creating tryptophan. The Salmonella kept copying the beneficial effects of the gene making tryptophan and over the course of 3,000 generations, the two functions diverged into two entirely different genes, marking the first time that researchers have directly observed the creation of an entirely new gene in a controlled laboratory setting.” There has been another interesting evolution experiment carried out using E. coli. The theoretical background to the experiment is as follows. It is generally assumed that a multi-step mutational evolutionary path is possible if all the intermediary steps are functional and can each be reached by a single mutation. The activity produced in this way may, however, be so weak that the cell must over-express the hypothetical newly formed enzyme — in other words, produce too much of the enzyme, causing a huge strain on the cell because it has to use extra synthetic capacity for this. Therefore it is likely that the cell would shed such a weak side-activity. The modest benefit wouldn’t be worth the strain caused by the overproduction. Ann Gauger and her colleagues studied what happened in such a case under laboratory conditions. They introduced a mutation that partially interfered with a bacterial cell’s gene for the synthesis of the amino acid tryptophan. Then they introduced a second mutation into the gene that completely abolished the ability to synthesize tryptophan. Cells with the double mutant could, theoretically, regain weak tryptophan-synthesizing ability with only one back-mutation. Given more time, cells with the one back-mutation might then undergo one more back-mutation to regain full tryptophan-synthesizing ability. This might demonstrate how a cell could gain a new function with just two mutations. But this did not happen. Instead, cells consistently acquired mutations that reduced expression of the doubly mutated gene. The experiment suggests that even if the cell could acquire a weak new activity by gene mutation, it would get rid of it because weakly performing functions of this sort exact too heavy an energy burden. So, while the described experiments are often promoted as evidence for neo-Darwinian evolution, they either (a) are intelligently designed and do not accurately reflect what happens in nature, or (b) underscore the narrow limits of neo-Darwinian evolutionary change.

Source: Cited to Attack Darwin Devolves, Study Devolves on Close Inspection | Evolution News

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