Some notable scientific hypotheses had been rejected for a long time before being accepted.
Meteorites Over the centuries, various people have venerated various meteorites as sacred stones. In the middle of the Grand Mosque of Mecca, there is the Kaaba, and in it, there is the Black Stone. It is likely a meteorite.
Around 450 BCE in Athens, Anaxagoras noticed some meteorite falls and he concluded from them that the Sun and the stars are very hot rocks.
But in the 18th cy., many scientists refused to accept the existence of extraterrestrial rocks.
1982Metic..17Q.295W Page 295 - The Eighteenth Century Meteorite Controversy: Aspects and Episodes But then
L'Aigle (meteorite) happened.
Quote:
In the early afternoon of 26 April 1803 a meteorite shower of more than 3000 fragments fell upon the town of L'Aigle in Normandy (France). Upon hearing of this event the French Academy of Sciences sent the young scientist Jean-Baptiste Biot, to investigate that spectacular fall of stones. After painstaking work in the field he reported two kinds of evidence pointing to an extraterrestrial origin for the stones:- Physical evidence: the sudden appearance of many identical stones similar to other stones fallen from the sky in other places
- Moral evidence: a large number of witnesses who saw a "rain of stones thrown by the meteor"
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Source:
M. Gounelle. The meteorite fall at L'Aigle on April 26th 1803 and the Biot report. Thus making a convincing case for the extraterrestrial origin of meteorites.
Some UFOlogists have argued that the scientific community's skepticism about extraterrestrial spaceships is as wrong as its former skepticism about extraterrestrial rocks.
Geological catastrophes There are numerous departures from strict geological uniformity that people have observed over the millennia. Floods, earthquakes, volcanic eruptions, landslides, meteorite impacts, ... But have there been catastrophes much larger than the ones that have been observed over the better-documented parts of humanity's history?
Lots of myths and legends would say yes, like various flood stories, and in the early 19th cy., many geologists believed that the geological record had been shaped by such catastrophes.
But in 1830 - 1833, Charles Lyell published his big book
Principles of Geology, subtitled "An attempt to explain the former changes of the Earth's surface by reference to causes now in operation". Not only was he usually very successful, his work made catastrophism seem like pulling rabbits out of hats.
But over the 20th cy., geologists came to recognize that these backward-extrapolated mechanisms coexisted with various catastrophes much bigger than any known from reliable history, like large glacial-dam-break floods and large volcanic eruptions and large meteorite impacts. They did so not from grandiose philosophical arguments, but on empirical grounds. They discovered that these large catastrophes were the best fits to their data.
Continental drift For over 4 centuries, various people have noted that South America fits into Africa, and some of them have proposed that Africa and South America had drifted apart. The first to develop the idea in detail was Alfred Wegener in 1912, showing that it can account for various geological and biogeographical similarities.
However, his proposed mechanism for continents drifting was very implausible, and his fellow "drifters" did not do much better. How could a continent plow through oceanic crust? Furthermore, much of what Wegener cited as evidence could also be explained by now-sunken land bridges in the South Atlantic and Indian and Antarctic Oceans. That's not an impossibility; Beringia is a land bridge that is now under water.
But as geologists surveyed the oceans in the 1950's and after, they discovered no evidence of a sunken land bridge in the South Atlantic Ocean. It was as deep as other ocean floors, and its rocks were much like other ocean-floor rocks. But they discovered that the Atlantic Ocean had parallel magnetization stripes that were correlated with their distance from the Mid-Atlantic Ridge, and the rocks' ages were also correlated with that distance.
Evidence of climate variations had led some geologists to propose that the Earth's poles had wandered relative to its continents, and geologists looked for evidence of polar wandering in rocks' frozen magnetism. They indeed found it, and they also found that different continents had different polar-wander paths.
In the 1960's, geologists like J. Tuzo Wilson put the pieces of this puzzle together, and they came up with what they called "plate tectonics". The continents drifted, but they drifted along with nearby oceanic crust, rather than plowing through it. Oceanic crust is created at ridges like the Mid-Atlantic Ridge and destroyed in subduction zones.
Most recently, continental drift has been verified by VLBI observations, and by satellite observations, like with GPS satellites.
Geologists have also addressed a common criticism of continental drift, that it seemed to have started with the breakup of Pangaea, making the last 150 million years rather exceptional. They have found evidence of continental drift going back at least 3 billion years, meaning that the last 150 million years do not have exceptional continent behavior.
Endosymbiosis That was first proposed by Konstantin Mereschkowski in 1905, and it was proposed off-and-on until Lynn Margulis revived it in 1967. For a long time, a common theory of the origin of eukaryotic cells is that they developed a sort of bubble around their genetic material, with some bits of genetic material getting their own bubbles. This is the "autogenous" theory, of a cyanobacterium developing into a "uralga" (
JSTOR: Taxon, Vol. 25, No. 4 (Aug., 1976), pp. 377-390).
Back to Lynn Margulis.
On the origin of mitosing cells | Mendeley On the origin of mitosing cells [J Theor Biol. 1967] - PubMed - NCBI She was married to Carl Sagan at the time, thus her last name in the paper. She proposed that mitochondria, chloroplasts, and flagella were all descended from various prokaryotes, like chloroplasts from cyanobacteria.
It was rather controversial at the time, but biologists were developing the ability to sequence genes as well as proteins, and they discovered that genes of mitochondria and chloroplasts are much closer to prokaryotes' ones than their cell nucleus's counterparts. So by the early 1980's, their endosymbiosis had become widely accepted, and that conclusion became stronger and stronger as the years went by and biologists became better at sequencing genes. In fact, biologists have identified the closest relatives of mitochondria: some alpha-proteobacteria.
Hpwever, the hypothesis of the endosymbiotic origin of flagella has not gotten much acceptance, though the eukaryotic flagellum's origin is still not very well understood.
Transposons: "jumping genes" Barbara McClintock first discovered them in 1948 as a result of her experiments with cross-breeding American corn (maize). However, her colleagues could not understand her work very well, and she stopped publishing it. But when her colleagues discovered transposons in bacteria and yeast in the late 1960's, they discovered that she had been there first.
Chemiosmotic biological energy metabolism Around 1960, biologists studying energy metabolism faced a quandary. They knew of two parts of it, but they could not figure out how they were coupled.
The first part of it is electron-transfer systems. For combining food molecules with oxygen, electrons are extracted from those molecules and sent down a "respiratory chain" to extract their energy. At the end, they are combined with oxygen and hydrogen ions to make water. Photosynthesis involves similar electron transfer systems, though with electrons coming from water molecules and the like, and getting energized by photons.
The second part of it is ATP, adenosine triphosphate. This RNA nucleotide gets extra phosphates attached to it to store energy; the energy resides in the phosphate-phosphate (pyrophosphate) bonds. This energy is then tapped for doing various biosynthesis reactions, muscle action, and the like.
How were they coupled? Many biologists thought that there was some chemical intermediate, though they could not find that intermediate. But in 1961, Peter Mitchell proposed his chemiosmotic hypothesis. It states that there is a physical intermediate instead of a chemical one, that electron-transfer systems push hydrogen ions outside of the cell's membrane. They can then return in a process that assembles ATP molecules.
This hypothesis was not widely accepted at first, but over the years biologists continued to fail to discover that chemical intermediate. However, they discovered a lot of things that were most consistent with chemiosmosis, like the ATP-assembling molecule, ATP synthase. By the mid 1970's, it was widely accepted, and in 1978, Peter Mitchell got a Nobel Prize in Chemistry for it.
