Any other scientific paradigm overturning as dramatic as "infections cause ulcers" in last 40 years?

This example

Helicobacter pylori

is often cited as the archetypal example of a scientific paradigm being overturned in modern times. Any other examples like this of huge revisions in scientific models in the last 30 -40 years or so?

Autism is caused by bad parenting-- specifically “refrigerator mothers.”

That one might be slightly outside your 40-year mark, but it depends on who you talk to. Many people still believed autism was caused by some kind of emotional disturbance or trauma into the 1980s.

Another one that is more limited in scope was that signed languages, like American Sign Language, aren’t real languages, because they supposedly lacked grammar and other markers of true languages, and functioned more like pidgins. ASL was, ironically, fully accepted by linguists in the 1970s, but not by educators of the Deaf (as a monolithic entity-- not as individuals-- many individuals were advocating HARD for its use in the classroom) for another 20 years.

Also a bit outside the timeframe, though not by much, but how about plate tectonics?

Not so long ago the maxim in genetics was that environment experienced by the parent was not reflected in the offspring. Since then we have started to gain an understanding of how epigenetics can shape gene expression in offspring, and that certain environmental factors experienced by the parent can show up as genetic changes inherited by their children.

That is a muddled article, rather typically reflecting widespread misconceptions and exaggerations about epigenetics.

First of all, it has always been obvious that gene expression is affected by the environment, including the intrauterine environment. It would be a little crazy to think otherwise. And, of course, parents are part of their children’s environment after birth. We have long known that the “CPU” of gene regulation is principally (protein) transcription factors, not epigenetics. In gene regulation, epigenetic marks are usually no more than a downstream effector mechanism, controlled by the transcription factors.

So, any notion of a paradigm shift does not relate to the general notion that the environment affects gene expression. It relates much more specifically to the possibility of transgenerational epigenetic inheritance. In other words: the parental environment affects gene expression in the parent’s DNA, mediated by an epigenetic mark; then this epigenetic mark is passed stably through the germline (via the DNA in eggs or sperm) onto the offspring’s DNA, and perhaps even into subsequent generations. This, if it happened, would be genuine Lamarckism.

There are animal studies that show that transgenerational epigenetic inheritance can occur, although epigenetic marks are never stably inherited for more than a few generations. This is still important, but if the marks do not persist they not significant in evolution. There are, so far as I’m aware, no human studies that have shown the epigenetic inheritance of any trait unequivocally, largely because outside the lab it is extremely difficult to control for environmental effects and inheritance via cultural/behavioral mechanisms.

So, epigenetic inheritance is an interesting field of research; it does occur to a limited extent in non-human animals, and most likely to some extent in humans; but we have no idea yet if it is at all significant, and there is no evidence at all that it is a factor in evolution. Based on the evidence so far, the notion that there has been an epigenetic paradigm shift is in my opinion a wild exaggeration.

Same people that claim Heartburn or Gastroesophageal Reflux disease (GERD) can cause cancer if the acid reflux is not treated.

Or stomach ulcers can cause if the ulcers are not treated.

Not to say how people believe personality traits are because of it.:(:frowning:

Example your Dad or Grandpa likes to drink pop and likes to fish and loves skydiving!! A war breaks out or a disaster and you get put in foster care. When you get older you like fishing and skydiving.

Prions were dramatic enough to earn a Nobel Prize for their discovery. When they were first described, many respected scientists were incredulous that infectious disease could be caused by something just the size of a protein.

This one doesn’t matter to anyone much, but:

Amdahl’s law

Amdahl’s law is a theorem of Computer Science, dealing with parallel computing. And it’s still valid: it hasn’t been overturned.

But the paradigm associated with it was overturned. Specifically, the idea that Amdahl’s law mattered. It doesn’t. It turned out that it doesn’t matter. We know now that it doesn’t matter. It doesn’t matter.

Amdahl’s law is the observation that when you parallelize computing, there is an irreducible fraction which cannot be paralleled, that you can’t reduce the time to zero, that the maximum speedup is a factor which is less than infinity. We all learned this in school.

But it turns out that almost no-one cares. That’s not what people want. If you can do it in 5 minutes, or an hour, or a day, that’s good enough. What you need, what people pay for, is to have more points. More resolution. More accuracy.

In weather prediction, more points gives you better prediction, and you need to do tomorrows forcast before tomorrow. If you are building nuclear bombs, you want the calculation to be correct, and you want it before you design the next bomb.

People still pay big money for parallel computing facilities, and there is no problem for which there is an irreducible minimum: people still want wider computing with more points.

Anyway, it was a dramatic reframing for me…

Might be looking at another paradigm shift there.

Might be looking at another paradigm shift there.

Umm… what? This post doesn’t make any sense. “points” isn’t a defined term in computer science.

Amdahl’s law is still hugely important in CS. We have a small range of algorithms that are massively parallelizable and have been vastly accelerated by the development of supercomputers. We have a much larger range of computation that is incredibly difficult to parallelize and there’s active research into how to make them more parallelizable.

That a “low fat” diet is the most healthy diet.

Would dark matter and dark energy qualify? Perhaps they must first be fully understood?

The idea is (I think), that Amdahl’s law is valid for any given problem of a fixed size (for example, an atmospheric simulation that calculates results every hour for points 10 miles apart) - for such a problem there will be an irreducible amount of unparallelizable operations, limiting the improvement that you can get from adding more parallel processors. But in practice, people don’t have problems of a given size - they want the solution for the biggest problem they can get a solution for, and adding computers does help with that (by example, making it possible to get results of an atmospheric simulation every 10 minutes, for points every half mile, in a reasonable time).

See also Gustafson's law - Wikipedia


I think that much larger than epigenetics was the discovery that the “junk”, that is non-coding, DNA wasn’t junk, but was heavily involved in gene expression. After Watson and Crick, biochemists widely assumed that each gene coded for a protein and that those proteins were all that mattered. I think this change is within the 40 year limit, although maybe just barely.

More like 60 years ago, was the discovery of asymmetries in charge, time, and parity reversals, although CPT reversal is symmetric. I think this was a real revolution in physics.

And not much more than 20 years ago, the acceleration of the cosmic expansion was discovered. This was a revolution in astronomy. The surprising thing about it was that it was accepted almost without opposition. That happened, at least in part, because two different groups came up with the theory using somewhat different methods. But it was entirely unexpected. Unlike, say, the discovery of the Higgs particle and gravitational waves both of which had been widely predicted.


RivkahChaya was saying that the prior paradigm that autism is caused by bad parenting has been overturned.

Maybe I’m not reading the OP correctly … but the recent discover of the on-going inflation of the universe kinda sorta changed everything in physics … dark matter, dark energy … unheard of 40 years ago I do believe …

Probably you mean the accelerating expansion of the universe? This had important implications for dark energy, but not so much dark matter (there are other lines of evidence for the latter).

The theory of inflation is something else.

Another vote for the new understanding of “junk” DNA.

With regard to Amdahl’s Law, it is a simple statement, and still important. I don’t think anything has happened that wasn’t obvious to Gene Amdahl when he first stated it.