Scientific Claims Are Reversible

How much confidence can the public put in scientific claims today, given that some long-lived dogmas have been reversed?

Sodium reversal:  Jesus said, “Salt is good” (Mark 9:50), referring to spiritual seasoning.  Scientists, speaking of dietary seasoning, have long proclaimed “Salt is bad,” urging people to reduce sodium intake drastically.  For instance, Medical Xpress continues to warn that “9 out of 10 American kids eat too much salt,” based on government guidelines.  But just the previous day, Medical Xpress reported that sodium’s influence on blood pressure (one of the chief worries) is negligible.  In a large study, sodium intake had an insignificant effect on systolic blood pressure among 8,670 French adults monitored for body mass index, fruit and vegetable consumption, exercise and sodium intake.  None of the participants were taking blood pressure medicine during the experiment.  This contra-consensus finding is important, the researchers felt, because “though the lifestyle factors measured in the study are often targeted by physicians as areas for adjustment in patients with hypertension, there is surprisingly little data on their individual effects on blood pressure within pharmacologically untreated populations.”  In other words, salt’s risk to blood pressure appears to be a commonly-accepted truism with little evidential support, leaving open the possibility that some people may be getting too little of the mineral.

Volcano reversal:  The “textbook theory of volcanoes may be wrong,” Science Daily announced, publishing a press release from Caltech.  Mantle plumes do not rise up through narrow jets to the surface.  The opposite is true:

The new measurements suggest that what is really happening is just the opposite: Instead of narrow jets, there are broad upwellings, which are balanced by narrow channels of sinking material called slabs. What is driving this motion is not heat from the core, but cooling at Earth’s surface. In fact, Anderson says, the behavior is the regular mantle convection first proposed more than a century ago by Lord Kelvin. When material in the planet’s crust cools, it sinks, displacing material deeper in the mantle and forcing it upward.

Caltech geophysicist Don Anderson is calling this “top-down tectonics.” He says it is “based on Kelvin’s initial principles of mantle convection.”  But then, how and why did the mantle plume hypothesis gain such traction for so many decades?  Anderson’s answer sounds disgustingly familiar:

“Mantle plumes have never had a sound physical or logical basis,” Anderson says. “They are akin to Rudyard Kipling’s ‘Just So Stories’ about how giraffes got their long necks.“

Neuroscience reversal:  A potential paradigm shift is in progress in neuroscience.  On PhysOrg, John Hewitt discusses recent findings that show neural pulses can pass through each other and continue on, contrary to a long-held belief that they annihilate on collision.  That sounds minor, but Hewitt claims it is “shaking the foundations of neuroscience.”  Since 1949, neuroscience has accepted the results of Ichiji Tasaki’s experiments that seemed to show annihilation.  “In other words, he was the man with the plan,” Hewitt says, showing the power of authority in science.  “If Tasaki found that spikes failed to penetrate each other then that would be good enough for me, and in fact it was good enough for neuroscience for the next half a century.”  The old view also comported well with existing theory.  New experiments by Thomas Heimburg may bring that dogma crashing down.

Mammal reversal:  Heard the one about mammals being small, shrew-like animals scampering in the underbrush to escape dinosaur feet?  Three new fossils described on National Geographic are “revising our image of the first furry beasts,” the article says, showing squirrel-like mammals with long toes and prehensile tails happily living in the trees. “Three newly described species suggest that mammals evolved earlier, and faster, than previously thought.”  The old picture of mammal evolution “needs to be repainted,”  now that we can see they lived in various habitats.  “They walked on the ground; they also swam, dug to burrow, and glided in the forests,” the article says.  This paradigm shift also shows that mammals were diverse and well adapted at their first known appearance in the fossil record.  How long before the museum displays are updated to include a variety of mammals?  Some scientists are likely to be unhappy with the “shifting picture of mammal evolution” —

“I expect this will be contentious,” [Anne] Weil [of Oklahoma State] says, but the study is an important addition to investigations of where mammals came from.

“I think it’s going to be part of an argument that will be going on for some time,” Weil says, “and I expect paleontology as a whole will learn a lot from questions gleaned from these animals about the antiquity of Mammalia.“

PhysOrg, reporting on the three new fossils, adds that these new species (1-10 oz. in weight) had complex teeth and the typical mammalian middle ear with three ossicles.  Their advanced state requires proposing a much earlier date for the first mammal common ancestor, at least 25 million years earlier, or as much as 74 million:

However, the placement of the new species within Mammalia poses another issue: Based on the age of the Euharamiyida species and their kin, the divergence of mammals from reptiles had to have happened much earlier than some research has estimated. Instead of originating in the middle Jurassic (between 176 and 161 million years ago), mammals likely first appeared in the late Triassic (between 235 and 201 million years ago). This finding corresponds with some studies that used DNA data.

Genetics reversal:  In “Biology’s Quiet Revolution” on Evolution News & View, Dr. Jonathan Wells recounts the major reversal in molecular biology since 1980.  Prior to that, scientists were confident they understood the “Central Dogma” of genetics, “DNA makes RNA makes protein makes us” – a concept amenable to genetic determinism and neo-Darwinism.  In a verbal victory dance, Jacques Monod proclaimed in 1970, “the mechanism of Darwinism is at last securely founded, and man has to realize that he is a mere accident.”  That was then.  Now, Wells shows with links to major papers, geneticists have repeatedly been astonished at major finds that have undermined much of the 1980s consensus, showing that the level of information in cells is much vaster than previously realized.  The Central Dogma has become “discredited myth,” Wells says, that must be discarded to answer the “huge questions” that remain.

But science is self-correcting!  Science has a method to avoid human bias!  Science is superior to every other method of discovering knowledge!  That notion is reversible, too.

It’s interesting that one of Lord Kelvin’s geological theories is being vindicated over a century after the fact (see our biography of Lord Kelvin).  Wells repeats a mythoid that Lord Kelvin was overconfident about science.  According to the citation, he said, “There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.”  Wikipedia says this about that oft-repeated joke: “The statement … is given in a number of sources, but without citation. It is reputed to be Kelvin’s remark made in an address to the British Association for the Advancement of Science (1900). It is often found quoted without any footnote giving the source.  However, another author reports in a footnote that his search to document the quote failed to find any direct evidence supporting it.  Very similar statements have been attributed to other physicists contemporary to Kelvin.”  The statement may well have been made by someone else and wrongly attributed to Kelvin; or, he may have been quoted out of context.