Imagine an animal that is incapable of digesting a particular kind of food. Now suppose the mutations for digesting that food were to suddenly appear within the population. There still has to be a corresponding change in the animal's behavior, correct?

I mean, I don't go around thinking, "Gee, how could I get the best out of my genes to get ahead of my competition?" There seems to be a need for changing behaviour to get the benefit of the new mutations, which for me allows room for divine providence (e.g. A God) to guide evolution at the level of animal behavior at least.

Am I missing something? Does evolution by selection not require device providence etc?

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    $\begingroup$ The fact that there is not, and there cannot be a scientific proof of God makes any (pseudo)scientific argument referring to God a moot point. If you want to explain something using science then you must stay in the framework of the scientific method. Putting God into the equation is a deus ex machina (pun intended) just doesn't work. You can of course explain evolution by means of divine intervention, but you cannot call that science. $\endgroup$ – nico Nov 19 '13 at 10:45
  • $\begingroup$ @Nico: I am aware of this. I was primarily interested in the philosophical underpinnings of the naturalistic worldview -- i.e. why certain scientists dismiss God from their personal worldview based on the science. (I initially wanted to post this in philosophy but I wanted a good answer to my question from the biology). $\endgroup$ – Joebevo Nov 19 '13 at 11:00
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    $\begingroup$ Why is it that at least 7 people have voted on answers but only I have voted on the question? Whether we agree with their worldview or not, the OP has asked a perfectly valid question in a non-confrontational manner and deserves an upvote. We should not refrain from upvoting valid questions just because we have a philosophical disagreement with the OP. $\endgroup$ – terdon Nov 19 '13 at 22:19
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    $\begingroup$ @terdon - I dont think it was a good question. For starters the title is "Why is there such an argument about evolution" but thats not what he is asking at all. Indeed, what he is asking is clear as mud. He first asks about how / if (?) genes can influence behavior. Not a bad biology question, but then he asks about why scientists ignore this, which is a wrong assumption, and not so much a biology question but a philosophical question about scientists. And he ends by asking if he is confused. Four questions if you count the title, none of them related. Im guessing thats why it got 0 upvotes. $\endgroup$ – von Mises Nov 27 '13 at 16:38
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    $\begingroup$ Understanding Evolution by UC Berkley is a very short and very introductory course on evolutionary biology that you might want to have a look at. $\endgroup$ – Remi.b Aug 18 '16 at 2:13

The theory of evolution via selection does not require any kind of divine intervention. It proposes that mutations randomly occur within the DNA, this causes changes in the phenotype (e.g. allowing digestion of a common food source), these changes can be good or bad (beneficial or deleterious). As a result, those with "good" mutations achieve more reproductions (the fitness of those mutant allele carriers is higher) and those mutations spread through the population. You can not direct the evolution of your DNA because mutation is random, even if we artificially induce mutations, we can not direct what the mutation does to the phenotype (though we can sometimes induce specific mutations known to have certain phenotypic effects). Selection favours some phenotypes over others but can only work with the mutations it is presented with - it can not direct the evolution of animals with wheels if mutations that allow wheels to form do not occur.

From this sequence you can see the evolution of a phenotype is best explained in a most parsimonious way without the inclusion of divine intervention. It is the principles of Occam's Razor. Calling divine intervention in to this theory would add further, and unwarranted, complication to the model and we would then have to find strong evidence for the existence of a divine being, something which is still yet to happen in the eyes of most evolutionary biologists. Strong evidence has been found which suits the theory without divine intervention (including unnecessary and untestable components to a theory goes against the basic principles of science).

Selection itself, though largely involved in evolution, is not necessary for traits to evolve. The neutral theory proposed by Motoo Kimura and developed in the last few decades suggests that traits can evolve with out selection, via genetic drift. This means traits develop in populations purely due to random sampling of neutral (or near neutral) random alleles. The relative importance of Selectionist vs Neutralist theories remains hotly debated within evolutionary biology.

Explaining your imaginary scenario with a current theory of evolution: A new digestive enzyme

The scene: There is a population of 100 deer. 50 males and 50 females. There is a potential for variance in mating success and that mating success is defined solely by the strength of the male.

Selection affects a trait: Males that digest their food better grow bigger and stronger. Thus selection favours males that get the most out of their food. If the ability to digest is completely genetically determined by a single locus (for simplification lets say it is) and there is only one allelic variant (one version of the gene) in our first generation then mating success will be equal among the males.

A mutant arises: In the next generation a single male carries a mutation in that locus. It is a mutated version of the gene which makes a key digestive enzyme work more efficiently.

Selection acts: This male is 10% larger and stronger than other males, and therefore sires more offspring in the next generation than any other male. These next generation offspring (technically half if it was a single mutation in a diploid organism - the other half have the ancestral haplotype) have the mutant allele. Then those males with the mutant allele also get more of the matings and so on and so on.

The allele is then spreading through the population. It will continue until all members of the population have the same allele (fixation) or will start over if a new allele arises which is even better. That's all evolution is, no divine beings necessary.

What if the allele was neutral? If the gene for a digestive enzyme existed but was not necessary in an organisms diet it would not know it could go out and use that food source. It may not even be able to. For example, a single fruitfly carries a mutation which has no cost and allows it to digest lactose. It is unlikely to be able to utilize that allele, because dairy products are not part of it's diet and not available in the wild. The allele would only drift in the population, eventually being lost (most likely as it starts at low frequency) or becoming fixed in the population. You can see a genetic drift simulation I wrote in R here. You can set f=1 and then play around with population size, number of generations, and replicates to get a feel for this process.

Note it is worth considering the effects of pleiotropy (if an allele has a good effect on one trait but a negative effect on another - including traits in different environments) and linkage (if the good allele is close to some deleterious mutations in the DNA it will struggle to spread until it is separated by recombination).

  • $\begingroup$ I think you might improve your answer by telling a bit about what might happen to newly arisen mutation that would be beneficial if the genetic background was different. What is the fate of this mutation allowing to create a new enzyme to digest a food when individuals behave (let's assume the variance in behavior are 100% genetically coded). You might as well give a word about pleiotropy. $\endgroup$ – Remi.b Nov 19 '13 at 9:19
  • $\begingroup$ The OP was asking what happen if the beneficial effect of the mutation (new enzyme allowing to digest a new food) is hidden because it is genetically coded that deer (to follow your example) don't eat the food it can now digest. In such a case, the mutation (new enzyme) is not beneficial and does not spread (or only by genetic drift). $\endgroup$ – Remi.b Nov 19 '13 at 10:54
  • $\begingroup$ It doesn't mean that you need a god for evolution to occur, it just mean that a mutation that allow better lactose (milk) digestion has a different effect on the reproductive capabilities of a mammal than of an insect. The effect of a mutation depends on the environment and the genetic background in which this mutation appears. $\endgroup$ – Remi.b Nov 19 '13 at 10:54
  • $\begingroup$ @Remi.b that's is covered by the neutralist side of things - "..traits develop in populations purely due to random sampling of neutral (or near neutral) random alleles" $\endgroup$ – rg255 Nov 19 '13 at 10:59
  • $\begingroup$ I felt that the OP might wanted a explanation of what might happen to the mutation he was talking about. I wanted to be specific to the OP's example where you provided very good general description. +1 good answer mixing basic process of evolution, philosophy of science and Kimura's neutral theory. $\endgroup$ – Remi.b Nov 19 '13 at 11:46

@rg255 already did a good job answering the main thrust of your question, I will address this part: "There seems to be a huge amount of room for divine providence to guide evolution at the level of animal behavior, at least. Why then do scientists with a philosophical materialist outlook gloss over this?"

Of course there is "room", there is room in the theory of evolution to posit that small, green, tasty but mean little pixies come and push the new food down the creature's gullets, thus teaching them to use new food sources. There is room to posit that invisible, intelligent lichen from Alpha Centauri are actually using brain waves to guide the evolutionary choices of species in a global scale.

While there is clearly room to posit these theories, there is absolutely no evidence for them. The scientific community is not "glossing over" anything, it is just ignoring various (infinite in fact) theories for which we have absolutely no evidence in favor of those for which we have. This is a classic fallacy that was very nicely put to sleep by Russell's teapot argument:

Many orthodox people speak as though it were the business of sceptics to disprove received dogmas rather than of dogmatists to prove them. This is, of course, a mistake. If I were to suggest that between the Earth and Mars there is a china teapot revolving about the sun in an elliptical orbit, nobody would be able to disprove my assertion provided I were careful to add that the teapot is too small to be revealed even by our most powerful telescopes. But if I were to go on to say that, since my assertion cannot be disproved, it is intolerable presumption on the part of human reason to doubt it, I should rightly be thought to be talking nonsense. If, however, the existence of such a teapot were affirmed in ancient books, taught as the sacred truth every Sunday, and instilled into the minds of children at school, hesitation to believe in its existence would become a mark of eccentricity and entitle the doubter to the attentions of the psychiatrist in an enlightened age or of the Inquisitor in an earlier time.

If you feel that the world you observe is best explained by assuming the existence of an omniscient god who guides the evolutionary process, then that is your right. However, the fact that you believe this to be true does not make it so any more than my believing it to be false disproves it. We are not glossing anything over when we don't take that belief seriously, no more than when we don't take Russell's teapot seriously. The Christian faith, like many others, is built on the assumption that a god exists, it will never attempt to prove or disprove that assumption because such proof would be sacrilege, the entire edifice is built on faith not evidence. If we do not share that belief, why should we attempt to fit our observations into the ideological scaffold provided by someone else's belief system?

If you feel that one theory explains what you observe better than another, the onus is on you to prove it so. That is in fact the beauty of science, it is what sets it apart from most other areas of human endeavor: we change our minds when presented with compelling evidence to do so. Indeed, the history of science is littered with discarded theories. If you can come up with any decent evidence to support a theory, then that theory will (eventually) be taken seriously. Until you do, asking others to consider it based solely on the fact that you believe it to be true is hubris to say the least.

  • $\begingroup$ This is a complicated topic. Basically, we differ on what can be known. Knowledge of God more properly falls into "personal knowledge", like knowledge of a particular person. You're quite right to demand a certain level of "proof"(proof, i.e. 100% certainty, only exists in mathematics), and for that I'd recommend Vishal Mangalwadi's "The Book that Made Your World". But to go from mere propositions about God to a personal understanding takes faith. $\endgroup$ – Joebevo Nov 20 '13 at 2:28
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    $\begingroup$ @Joebevo exactly, and as such does not fall within the purview of science. That's why nothing is being glossed over, faith is not something that can be approached by the scientific method of observable and repeatable experimentation. Therefore, any theories that base their conclusions on arguments of faith are not relevant to scientific debate. Science only deals with testable, disprovable theories and the existence of a guiding hand in evolution is neither. $\endgroup$ – terdon Nov 20 '13 at 2:38
  • $\begingroup$ But you can of course argue against the existence of god on the basis that in many religions there are beliefs in acts of god(s) or features of god(s) that are in opposition to scientific knowledge (walking on water, wine from water etc.). By asserting a level of probability on things that people say god does you can indirectly assert the likelihood of god existing in the first place. So because nothing god does / what god is is physically possible as far as science can tell, very likely there is no god at all. $\endgroup$ – yotiao Nov 20 '13 at 12:21
  • $\begingroup$ @yotiao well, not really, no. If you start with the premise that god(s) exist, by definition they are above and beyond the laws of physics. Therefore, you expect them to be able to do things that are impossible, otherwise they would not be gods. Deities are not expected to conform to the laws of Nature, they wrote them. $\endgroup$ – terdon Nov 20 '13 at 12:28
  • $\begingroup$ Heh, this is way OT so we should not go much longer, but I then ask: what is your argument for the premise (god(s) exist) in the first place? $\endgroup$ – yotiao Nov 20 '13 at 12:55

I think it pertinent to answer the question posed in the original title, although I will make passing reference to the specific argument the poster makes.

“Why is there such an argument about evolution?” This is because evolution is an example of a scientific question which one party approaches from a philosophical standpoint that asserts a particular answer, and so they will never be convinced by scientific arguments that ignore this philosophical position.

Note, that I am not saying that the arguments from those of a particular philosophical standpoint are necessarily wrong, only that its exponents will continue to argue (or try to engage people in argument) when the vast majority of scientists have come to regard the question as settled in favour of the counter-view — indeed when that view underpins their daily work.

There are other historical examples of this. Most well known is the Roman Catholic Church's refusal to accept Galileo’s espousal of the Copernican view of the Solar System — even to look through his telescope to see the evidence. (I think they have thrown in the towel on that one now.) On the political left you have the promotion of Lysenkoism by the Soviets.

I would suggest that philosophical attitudes colour contemporary arguments. I suspect many ‘progressives’ would never accept scientific evidence that indicated one ethnic group were less intelligent than another. And it would be naïve to think the stage at which one regards a life as having been formed is independent of any religious or feminist views one may hold. There now. I’ve lost the friends I made in the previous paragraph.

Finally, your example of an individual acquiring the ability to digest a different food illustrates my point. You are so convinced that you are right that you have never taken the trouble to find out what the arguments for evolution actually are. It is only under circumstances that an acquired trait provides a competitive advantage that it will be selected for. Think multi-drug-resistant bacteria. You’ll find much more sophisticated arguments on the various ‘scientific creationist’ sites on the Internet, but you would be advised to save your breath, because nobody is listening. As I said, la guerre est finie.


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