I’ve read before a few times something along the lines that the Theory of Evolution is the opposite of chance.
Let me get this straight, if it is the exact opposite as “chance”, then isn’t that saying that ‘natural selection’ is guided by some sort of purpose?
I guess i was under the impression that the mutations just “happen” and they only get “selected” if the organism survives and reproduces. Which could actually happen whether or not it is benificial (IOW, the mutation is not beneficial, in and of itself)… it only is beneficial after the fact… sounds like “chance” to me.
Also, Darwinian evolution “says” that all these mutations accumulate over time, until enough mutations occur for an actual change, and those changes accumulate until speciation (well, something like that… close enough)… but it implies that some of the accumulated mutations can be unbeneficial or even harmful… but it takes time before it matters one way or another. (i think this is pretty close, atleast close enough for the purpose of this thread).
Where have you read that? Evolution involves a great deal of chance.
Perhaps what you read was more along the lines of “evolution isn’t completely random”. Each individual mutation is random, but since bad mutations are quickly selected against the overall effect is not a random process.
No. Anyone is saying that doesn’t really understand how evolution works.
I don’t know what you mean by beneficial after the fact. Beneficial is beneficial. For example, a mutaton which allows someone to digest milk as an adult in a dairy-rich environment is a beneficial mutation. If food is scarse he can eat things that make other people sick, increasing his chances of survival and increasing the likelihood that he’ll pass that mutation on.
No. For selection pressure to work each individual mutation has to represent an actual change that effects survivability (or reproductive capacity). It’s not like the mutations pile up and then, boom, there’s a change. Each mutation is a tiny, tiny little change. Add up enough tiny changes and you get an organism that looks and acts very different from its distant ancestors.
A lot of creationists fixate on the mutation (chance) part and ignore the selection part, which is what the phrase is intended to convey. There is “some sort of purpose” choosing survivors, that purpose being “suitability for a given environment.”
The “opposite of chance” applies to selection, which is distinctly biased (i.e. not based on chance) toward mutations that are beneficial, and against those which are harmful (almost completely, over the long term).
If natural selection were pure chance (or more specifically, didn’t exist), there would be no species at all, because every weird mutation would be equally likely to produce offspring, and populations would rapidly become mixes of “whatever.”
For a more specific example: ostriches and penguins share a common ancestor, albeit a very long time ago. The fact that you find them now, non-intermixed, and mostly uniform in general appearance/behavior/etc. is because selection wasn’t based on chance, but rather very specific to the environments the populations found themselves in. Change the antarctic gradually to a desert, wait a few hundred million years, and (assuming the penguins survived the change – lots of species don’t) you’ll get “penguins” that look at lot more like ostriches than they do the penguins of today - not because of chance mutation, but because only those mutations helpful to survival get to be passed on.
Basically, your phrase is just acknowledging that selection is a much stronger force than mutation in speciation.
If you pour a bucket of water onto the side of a hill, it will all run down to the bottom. This isn’t due to chance. Neither is it due to any purposiveness on the part of the water.
Mutations can be beneficial or harmful. But a cat with better hearing or better endurance is going to survive to reproduce longer than one with bad hearing and the lung capacity of a gnat.
The mutation is random (to a certain degree; a cat won’t give birth to a hippo). The “selection” does not have a purpose. There’s no end goal. It’s just which living things survive to reproduce, and beneficial mutations help that while harmful ones don’t.
What Pocchaco said (vague but nice reference to recent discoveries on lactose tolerance in adults, btw). Also, keep in mind that all evolution does not occur through mutation, which is the result of errors in DNA copying during meiosis. Evolution also occurs through the random mixing of already available genes. That’s different. Also, very rapid evolution can occur when gene mutations occur such that not only is a new gene beneficial, but the new gene affects the meiosis process itself in such a way that the resulting cells (sperm cells, say) have the gene more frequently than half the time (which is normally the case). Example: person with brown eyes has gene for brown eyes and blue eyes (if memory serves, this is possible since the blue eyes gene is recessive). Normally, during meiosis, half his sperm cells have brown eye genes, the other half have blue eye genes. It’s possible (but very rare) for a mutation to occur such that the blue eye gene affects the meiosis such that 95% of the sperm cells have the blue eye gene. This odd and rare phenomenom is called segregation distortion. This can very rapidly spread a benefical gene throughout a species…OTOH, if the gene is harmful, it can wipe out a species in a few generations with no outside environmental change at all.
No. “By chance” is not the opposite of “having a purpose”. “By chance” simply means either that multiple results are more-or-less equally likely, or that we cannot predict the outcomes of multiple trials. The opposite of “by chance” is “predictable”.
Mutations occur when there is an error in DNA transcription. These mutations can result in a change in the phenotype of an organism, and that change could be advantageous to the organism, detrimental, or neutral. If the mutation is advantageous (based on the circumstances in which the organism finds itself), then the organism will likely have a greater than average chance to pass on that mutation to the next generation. As a greater percentage of the population acquires that beneficial mutation, the population is said to “adapt”.
If the mutation is detrimental, then the organism will likewise have a less than average chance to pass on that mutation. If the mutation is neutral, then its frequency in the population will vary more or less randomly.
Note, however, that all mutations are not equally likely. Some have a higher than average chance of occurring, some lower. There can also be constraints which limit the number of ways in which a trait can vary. For example, the number of fingers we currently have is likely limited by a constraint within a suite of homeobox genes, which control development. Because these genes represent a suite of developmental master genes, even a minor mutation could prove detrimental.
Really, what Darwin talked about was variation, not mutation. Variation was only later linked to mutations in the genome. The idea was that a slightly faster, stronger, smarter, whatever critter would have a slight advantage over its kin, and thus would be more likely to survive and reproduce. If that variation coule then be passed onto its offspring, they would then also be slightly faster, stronger, smarter, etc., and likewise have an advantage. Eventually, that variation becomes present in a high enough percentage of the population that it becomes the norm, rather than an oddity. Given enough time, then, even these small changes can add up to large effects.
Several excellent posts. I just wanted to add that each mutation has to be helpful (or at least neutral) or it will be selected against. Sometimes things can get complicated. Sickle cell anemia is very harmful, but it does not get selected against in areas that have high incidence of malaria since a single dose of the sickle cell gene is protective against malaria without causing the disease, while a double dose is very bad.
Another example. It would be much more “intelligent” if the optic nerve came out behind the retina (as it does in many orgamisms, for example, the octopus). But there would seem to be no sequence of helpful mutations that would get us there from here. (And how did the octopus get there? Doubtless through independent evolution. Eyes appear to have evolved independently at least 40 times in the course of evolution. Useful appendages.)
Evolution, as a whole, is indeed the complete opposite of chance. What does depend on a bit of randomness is the various mutations that occur between generations. Natural selection allows the good ones and kicks out the bad ones. What you’re left with is more complex, more adapted, and better suited species to the environment.
I’ve heard quite respectable people say this, and it is usually in response to the conflation of two creationist fallacies: first, that we were somehow inevitable, and two, that evolution is random. The 747 in a hurricane analogy is an example of these fallacies.
The lack of chance comes from the fact that any organism that successfully reproduces must, in general, be well adapted to its environment. The real chance comes from the fact that no one can predict which possible successful organism will wind up evolving. The tree of species is bushy, but the tree of potential species in the evolutionary search space is a lot more bushy, and which of the many potential paths that might be selected does depend on chance. The asteroid pruned a lot of potential branches in the search space, and that was definitely random.
I appreciate all the replies. I can’t get back to all of them, but after doing some lurking, it seems that Darwin’s Finch is one of the resident evolutionary experts on the board, so if you all don’t mind, I’m going to concentrate on replying to his post, and hopefully he’ll reply back.
And your point is??
Let’s put this in perspective…BrandonR
wrote, “Evolution, as a whole, is indeed the complete opposite of chance”.
And you say that the exact opposite of ‘chance’ is ‘predictible’… So what you are saying is that Darwinian ToE is predictible, but when i look at Wikipedia, it says:
Natural Selection is random in that you can not accurately predict the changes in nature… although that is getting easier the more that humans tamper w/ nature… IOW, humans are causing more of an effect, but that does not help the case of Evolutionary origins.
Genetic drift is also ‘chance’. As are copying errors, especially in light of the fact that the DNA has coding to “correct for mistakes”.
You say all this to refute what i said, but you just said the same thing as what i said:
“(IOW, the mutation is not beneficial, in and of itself)… it only is beneficial after the fact”
And we both could have used less words (since i had to say it twice)and said the same thing, had we copy/pasted the first sentence on the “selection” link in wikipedia:
How is “more or less randomly” not chance?
Again, this is, by effect, chance.
Irrelevant. Since Darwin was on the same track, it is saying basically the same thing.
One thing that i havent seen someone explain(and it’s possible that it has been, I just havent seen it) is that if mutations have roughly an equal chance of occuring, then along with the faster,stronger etc. genes, it would also mean that many undesirable traits get passed along… so in effect, also become more heritible.
No, beneficial traits are more likely to persist and detrimental ones less likely, because they can affect an organism’s viability with regard to survival and reproduction.
It doesn’t actually matter what proportion of the mutations confer positive changes, as long as there’s a mechanism (natural selection) that exists to weed out the bad ones more than the rest.
Certainly living things with nonbeneficial genes will be born, but it’s surviving to reproduce that’s the thing. You could have any number of slow, dimwitted antelope born, but it’s the fast and agile ones that won’t be caught by predators and so live to sire a new generation.
But beneficial and nonbeneficial is in relation to the environment. So a creature could have what would be considered a bad characteristic in one situation, but for the environment it is in it’s useful. Thicker fur is handy for arctic climates, but would be pretty unhelpful in hotter places.
A simple analogy is this
Imagine throwing 100 dice but taking only the 10 highest die. Though the system is pure chance (it is just dice) the fact that there is a chosing of the ‘best’ die results in the 10 chosen die being much less random. You can expect all 10 chosen dice to be 6s and you would be very surprised if the 10 chosen highest would contain any 4s 3s 2s or 1s.
Similarly mutations are random, but survival pressures result in only the better mutations surviving to reproduce enough to become common.
You flatter me unduly, methinks. There are many others here, at least as knowledgeable and possibly moreso than myself.
My point is exactly as I stated it: the opposite of chance is not “purpose”, it’s “predictability”. Evolution has a significant random component to it, as well as a predictable process (in terms of mechanism) underlying population changes. However, the process is in no way “purposeful”.
Natural selection is not “random” in any statistical sense. It is the process whereby those individuals within a population who, by virtue of their particular traits, have an edge – even if it is but a very slight edge – over their fellows in the competition for resources (e.g., food, territory, mates, etc.). That edge gives them a higher-than-average chance of mating. If their advantage is heritable, then their offspring will likewise posses that advantage. Note that there is still a lot of probability in play here; NS is not a guarantee of anything. It’s a stacking of the odds in favor of those with traits which assist one in a particular environment, and against those with traits which are harmful given their environment. Even the bestest and smartest and fastest can still get crushed by a falling tree in their sleep.
Genetic drift is, indeed, effectively random. But it is not the primary mechanism of evolutionary change. Mutations and variation are also largely random, but they simply provide the pool upon which NS operates. Each possible variation does not have an equal chance of appearing, nor does each appearing variant have an equal probability of being selected for or against.
Well, no, it’s not beneficial “after the fact”, it’s beneficial (or not) in the here and now. A given variation may appear regardless of the environment, but it is the environment which determines whether that variation is beneficial or detrimental. Some mutations are detrimental no matter what, in that they may prevent the organism from developing properly.
I don’t believe I implied anything otherwise… Again, my point is not that there is no chance or random component to evolution; it’s that “purpose” is not the opposite of “chance”. Evolution has elements of chance, of randomness, of predictability, but none whatsoever of “purpose”. But keep in mind also that NS is not solely random; it’s a stacking of the odds in favor of or against certain possible outcomes. Change can directional and guided in a sense, but it is still without purpose.
Not really. Variation can come from multiple sources. Mutaions and variation are not interchangeable; natural selection technically acts upon variation, not mutation, and mutation is but one source of variation.
Well, as I mentioned, all mutations don’t have a roughly equal chance of occurring. And, some undesireable mutations will persist in the population, sometimes for many generations; no individual organism is perfect. As I mentioned, NS is not a guarantee of anything. Furthermore, the agent of selection as I see it is the organism itself (many of course, will disagree…). As a result, you either keep or lose the whole genetic package. So, one may well be faster and stronger and smarter, but also have an immune deficiency or some such. Whether that organism winds up passing on its genes will depend on how big a deal the particular detriments are relative to the benefits. A slight change in the environment can turn a previously minor detriment into a major one, or a previous advantage into a disadvantage, or a previous detriment into a benefit, or… You get the idea.
So, to sum up: evolution has random components, and not-so-random components. The process of natural selection is not itself random, and the results are that populations adjust to better “fit” the environment over time. Other mechanisms, such as genetic drift, are effectively random. Variation can be random, random with constraints, or so constrained as to be very limited.
Evolution is not the “exact opposite of chance” (whatever that really means…). It does have some elements of predictability, and is, in a sense, guided by the ever-watchful, overly-anthropomorphic eye of natural selection. But it is not directed toward, or by, any purpose.
A decent analogy, but I would add that there is no law that says the highest die is in any way “better.” Indeed, by defining it so, we have given die evolution a purpose. It could very well be that the environment of the dice favors 2s instead. It could be that 3s are favored, but eventually the environment changes so that even numbers are favored. Species of 2s and 4s may result as offspring of 3s.
While I don’t doubt this on a general level, won’t more dramatic changes have a better chance of sticking? It seems to me that an African leaping snail that can evade predators by leaping an extra .0000000001 millimeter further than its peers has gained no significant survival benefit. That tiny little change would have no real chance to accumulate.