Falsifiability of evolution

{{bronze}}{{evolution}}
The '''falsifiability of evolution''' is an important part of establishing [[evolution]] as a [[scientific theory]] on the principles of [[falsifiability]]. Creationists and others sometimes claim that evolution and [[common descent]] cannot be falsified and consequently are not science.<ref>[[cp:Falsifiability of evolution|Falsifiability of evolution]] at Conservapedia</ref> In other cases, [[intelligent design]] advocates insist that there is no way to falsify evolution because any new evidence just becomes "evolution in action" anyway.<ref>[http://darwins-god.blogspot.com/2010/12/arsenic-based-biochemistry-turning.html Darwin's God - Arsenic based biochemistry, turning poison into wine.]</ref> 

This, however, is simply not the case, as there are numerous pieces of evidence that could falsify evolution if they existed and were discovered. The assertions made by creationists may be due to a misunderstanding between the concept of "falsifiability" and "has been falsified". More intelligent criticisms of the falsifiability of evolution focus on how new evidence (such as new fossil or climatology data) always leads to evolution and never towards design, even when theories about specifics of a species' development are changed significantly in light of evidence. However, this is a case of the [[science was wrong before]] gambit, and has little to do with falsifiability itself.

==What would falsify evolution?==
A central characteristic of [[science]] is that it must be [[falsifiable]]; this feature of a [[theory]] is attributed to [[Karl Popper]], who mentioned it in {{wpl|Karl Popper#Origin and evolution of life|a criticism of Darwinism|.}} Scientific theories cannot be [[proof|proven]] outright — they can only fail to be disproven, and this means pointing out what [[evidence]] could disprove the theory. If a theory cannot be disproven, such as with [[Russell's Teapot]], it makes no difference whether it is true either way.

Disproving evolution first requires one to look at what the theory predicts and see where it can be shown to make incorrect predictions. It is easy to be side-tracked by specifics of the theory, such as individual evolutionary pathways of certain features, and confuse these with what would falsify the overall theory of evolution by natural selection. Indeed, many creationists do this whenever a new discovery is made in biology that causes scientists to rethink some pieces of evolution. To avoid this problem, it is best to be clear what evolution is. It is based on three main principles: variation, heritability, and selection. Given these three principles, evolution ''must'' occur, and many features of evolution appear given only these three guiding principles.<ref>[https://www.youtube.com/watch?v=mcAq9bmCeR0 Evolution is a blind watchmaker]</reF> If any of these were shown to be flawed, then the theory would be untenable. 

Consequently, any of the following would destroy the theory: 

*If it could be shown that organisms with identical [[DNA]] have different genetic traits.
*If it could be shown that [[mutation]]s do not occur.
*If it could be shown that when mutations do occur, they are not passed down through the generations.
*If it could be shown that although mutations are passed down, no mutation could produce the sort of [[Phenotype|phenotypic]] changes that drive [[natural selection]].
*If it could be shown that selection or environmental pressures do not favor the reproductive success of better adapted individuals.
*If it could be shown that even though selection or environmental pressures favor the reproductive success of better adapted individuals, "better adapted individuals" (at any one time) are not shown to change into other species.
[[Charles Darwin]] made the case a little differently when he said, "If it could be demonstrated that [[Irreducible complexity|any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications]], my theory would absolutely break down. But I can find out no such case."<ref>[http://www.bartleby.com/11/6005.html Origin of Species]</ref>

===Precambrian rabbit===
[[Image:Precambrian rabbit rawr 1.jpg|thumb|A Precambrian rabbit not disproving anything.]]
[[J. B. S. Haldane]] famously stated that "fossil rabbits in the Precambrian" would disprove evolution — and this has been a talking point in philosophy of science for some time. This phrase is reported to be a rebuttal to the accusations that evolution is not falsifiable. However, the reality of disproving evolution in this manner is quite complicated. As science is based on an interplay between [[theory]] and [[evidence]], [[One single proof|a single point of data]] is not enough to completely destroy a theory — just as much as even an excellent theory can't win out against overwhelming data. Such a thing as finding fossilized rabbits wouldn't cause scientists to throw the theory of evolution out completely and immediately, so a little more explanation is needed.

First of all, it must be remembered that the [[fossil record]] is merely ''supporting'' evidence for evolution. This is contrary to the ideas put forward by creationists that state that the gaps in the fossil record prove evolution to be false. If the fossil record simply did not exist, it would make no difference to the validity of the theory of evolution — indeed, the hypothesis of natural selection was initially formulated ''without'' the aid of the fossil record, and subsequent DNA evidence can stand completely without it. The simple truth is that a ''single'' strange fossil would probably not make much difference. In practice, the evidence in the fossil record which supports evolution is so overwhelming that a single fossil would definitely be regarded as curious (read: strange), but compared to the mountain of evidence in favor of [[evolution]], it would probably be regarded as an anomaly while more data was awaited. Imagining the fossil rabbit in the Precambrian as disproving all of natural selection would confuse the specifics of an individual evolutionary pathway with the falsification of the whole theory itself, as mentioned above.

However, the existence of ''entire groups'' of anomalous fossils would be a different thing — Haldane did say rabbit'''''s''''', after all. Again, in practice, an effort would initially be made to fit the new data into the existing framework — this is not cheating, but simply the way science works. But still, in principle, some quite major revisions to the theory may be needed to explain them. Such a situation would '''not''' immediately and conclusively prove a special creation over a naturalistic evolution, however, a key point that creation proponents 
tend to
 stubbornly overlook. Eventually, a new theory would develop to include these oddities, but this isn't necessarily a special [[young Earth]] creation, as this assertion would also require supporting evidence, and lots of it. Perhaps this anomalous group was due to a now extinct [[second genesis]], which would be a remarkable find, but unlikely to disprove evolution outright. Regardless of what it was, this new theory would explain both the evidence we have now ''and'' the hypothetical rabbit fossils and would indeed be science fully supported by evidence.

===Predictions===
Some creationists have claimed that true [[science]] must make [[prediction]]s, but [[evolution]] only describes what happened in the past, so it is not predictive.<ref>https://web.archive.org/web/20090122062251/http://www.answersingenesis.org/docs2002/0228not_science.asp</ref> However, this argument has several flaws:

# The argument is a [[Non sequitur|non sequitur]]. Evolution can be predictive, and yet still only describe what happened in the past. We do not have omniscient knowledge of the past, so we make predictions about what has already occurred. While this may sound nonsensical on its face, we make predictions about the past all the time in day-to-day life: "If he hadn't had car trouble, he'd have been on time", for instance.
# Many predictions are possible based on the theory of evolution (e.g., predicting germ/pest resistances to [[Antibiotic resistant bacteria|antibiotics]]/pesticides, predicting general traits/locations of future [[fossil]] finds, predicting population responses to selective breeding attempts, etc.)
# Just like meteorology only predicts effectively maybe a week into the future, evolution cannot be used to precisely predict what will happen in the future. It does, however, tell us what kind of changes can be expected to happen.
# There are many predictions concerning the future that can be extrapolated from the theory of evolution, even if they are not explicitly stated by [[Darwin]]. Here are some examples of predictions that one could argue would be extrapolated from the theory of evolution.
#* [[Species]] with high reproductive rates will have a better chance of surviving [[environment|environmental]] change than species with low reproductive rates.
#* Species from a common [[gene pool]] separated into group A and group B and isolated for generations over a longer period of time and exposed to different environmental conditions will eventually become unable to reproduce with members of the other group.
# It is possible to predict the outcome of a [[Macroevolution|macro-evolutional]] experiment, but it's a bit difficult to verify it. However, it is equally possible and valid to predict certain [[paleontology|paleontological]] findings.  Some of these are actually verified by now (like some kinds of [[fossil|fossils]]).
# Darwinian evolution predicts that all organisms on Earth derive from a common ancestor. This ancestor has not been identified through fossil records (and probably cannot be), but its existence is a necessary consequence of the fundamental genetic unity of all life on Earth.
# [[Creationists]] who use this argument [[psychological projection|
fail to realize
 don't know or care]] that there have been no scientific predictions made by [[Scientific Creationism]], and given that "[[Goddidit]]" is their explanation for '''everything''', it is ''impossible'' for them to '''''predict''''' anything.
# Evolution requires a huge amount of time to operate and thus effectively predicted that the [[Sun]] was powered in a far more efficient manner than previously thought — a prediction that was verified by the discovery of [[nuclear fusion]].
# Mendeleev only described what had happened in the past when devising the [[Periodic Table|periodic table]]. One prediction of evolution, amongst others, was that transition species would be found and added to the [[fossil record]], as they have been.

==What would falsify common descent?==
[[Common descent]] is the theory that all life evolved from one common ancestor, or groups of ancestors (although it is slightly more complicated than the [[straw man]] version of "one day a cell appeared and everything is technically its descendent"). Morphological and, more recently, genetic evidence puts common descent pretty close to being outright proven, but there are still ways to falsify it. Common descent could easily be disproven (without even seriously challenging the theory of evolution) if we discovered/made a form of life that was not related to all the life we know — most simply, by finding life that does not use the nucleic acids (DNA and RNA) for information storage and retrieval as known biological life does. This would be exemplified in the situation of a [[second genesis]], where two different forms of life began at two completely different points.

Also, if we were ever to discover [[exobiology|life elsewhere in the universe]], the odds lean towards it not having a common ancestor with life on earth. This would really only require that "all life" be modified to "all ''terrestrial'' life", and similarly, the second genesis on Earth would signify that two forms have two common descents.

==See also==
*[[Scientific method]]

*[[Kids! This site is all yours]]
*''[[What Darwin Got Wrong]]''

==External links==
*Claims [http://www.talkorigins.org/indexcc/CA/CA210.html CA210 (lack of predictions)], [http://www.talkorigins.org/indexcc/CA/CA211.html CA211 (falsifiability)], and [http://www.talkorigins.org/indexcc/CA/CA211_1.html CA211.1 (Popper)] at [[Talk Origins]]
*[http://www.talkorigins.org/faqs/comdesc/ "29+ Evidences for Macroevolution: The Scientific Case for the Theory of Common Descent with Gradual Modification" (1998)], Douglas Theobald
*[http://www.talkorigins.org/faqs/evolphil/predict.html ''Evolution and Philosophy: Predictions and Explanations'' (1997)], John Wilkins

==References==
{{reflist}}

{{crebox}}