Rumraket wrote:Thanks for your responses susu.xp. It got me wondering, do you know of any studies done on to what extend mutations are caused by different environmental factors, such as radiation, chemical pollution, heat-shock induced mistranslations etc. etc. ? Furthermore, have studies been done on to what extend these different factors contribute to the natural variation and thus evolution?
I found this strange article a few days ago which seems to argue that speciation rates depend in large part, directly on the average temperature of the environment: http://www.pnas.org/content/103/24/9130.full.pdf+html

I´m not aware of such studies, though there certainly are some (it´s simply not something I´m well read up on). The article seems somewhat strange and I´ll have to re-read it, but one issue I have here is the way they use speciation there - it´s applied to types, which are likely not actually species.

willhud9 wrote:Let us take the flipping the coin. If I flip a coin I will result in 2 known variables, heads or tails. Probability: that is 1/2 heads, 1/2 tails. The random variable comes from a random process. Let us flip 2 coins (red coin, blue coin) and see what the possible answers are (R-H, B-T), (R-H, B-H), (R-T, B-T), (R-T, B-H) Any one of those is a random variable. If you cringe at the term random than use stochastic since a random variable is a stochastic variable.

Not quite. These are possible outcomes of a random trial and you associate outcomes with values of the random variable. I.e. the random variable is one that has one of several possible states, the states themselves aren´t the variable. I know the definition given was somewhat abstract, but you do sacrifice something if you don´t use it - there are quite a few bits that are required to keep it both general and stop it from "blowing up" in some way in actual use.

Oldskeptic wrote:What I get out of all this is that "random" simply means difficult or impossible to predict given our input.

No, it means impossible to predict. Difficult to predict isn´t what a random variable deals with.

Oldskeptic wrote:Which is what I have been saying. It is where the probabilities cannot be measured easily or at all.

The probability of a random variable can be known precisely. There´s a simple generator for a random variable which is 1 and 0 with a probability of precisely 0.5 each:
1) Throw a coin.
2) Throw a second coin.
3) The variable is 1 if the first coin is heads and the second is tails, 0 if the fist coin is tails and the second is heads. If both coin tosses show the same face, repeat from 1.
In this case we know the probabilities precisely, still we have a random variable (and neatly enough an infinite string of these interpreted as the binary representation of a real number beyond the binary point gives us a variable with a uniform distribution in [0,1], which in turn can be transformed using a particular class of functions to generate a random variable with any type of probability distribution).

Oldskeptic wrote:What is wrong with that genetic mutations are unpredictable rather than saying that they are random?

Well, random variable is the technical term. stochastic variable is synonymous, but used less often (the reverse is true with random/stochastic processes).

Oldskeptic wrote:To me random means happening for no reason at all, and this is the meaning that creationists use. Am I wrong?

TBH I´m not sure what creationists mean when they use the term. I´m not sure how it´s used by people who state that selection sin´t random, either. Random does mean devoid of sufficient cause, it does not mean devoid of neccessary cause (i.e. for a random variable to take a particular value this value must be in the sample space for the variable - that´s a minimum condition, in the case of discrete RVs we also need a probability greater than 0). That´s what I was refering to earlier - classical physics envisioned a universe where causes were sufficient and there were philosophical arguments that there had to be something which didn´t have a sufficient cause - god. Darwin introduced a causal mechanism that was not driven by sufficient causes and physics now runs entirely on neccessary causes.

Oldskeptic wrote:Is evolution a random process? That is the question. I say no. What say you?

Sure. Though here stochastic process is the more commonly used term.

The conflation of “chance” in evolution

Discussions of “chance” and related concepts (such as “stochasticity,” “randomness,” “indeterminism,” etc.) are found throughout philosophical work on evolutionary theory. By drawing attention to three very commonly-recognized distinctions, I separate four independent concepts falling under the broad heading of “chance”: randomness (as a property of sequences), epistemic unpredictability, causal indeterminism, and probabilistic causal processes. Far from a merely semantic distinction, however, it is demonstrated that conflation of these obviously distinct notions has an important bearing on debates at the core of evolutionary theory, particularly the debate over the interpretation of fitness, natural selection, and genetic drift.

So which meaning of "chance" (or "random") is each person in this thread using?

I'm mostly a statisticalist, because I don't think that it is necessary to know what is ontologically real (or even if there is an ontologically real objective universe "out there") to do science. If what we observe is sufficiently described by a given hypothesis, we don't have to go on a philosophical goose chase to fit reality to our perception of the way that reality should be.

I´m coming down heavily on the causal indeterminism front.
While I agree that an ontological position isn´t neccessary for science, we can still rule out some ontological positions given a particular phenomenal world. Since we can assume that there is a relation between the two and that the relation itself has to be implemented in some way in reality, we can note that a causal indeterminist phenomenal world implies a causal indeterminist reality, since you can´t use a deterministic realtion to transform a deterministic variable into a random variable (the law of large number allows the inverse transformation though, that´s why there´s only an implication, not an equivalence).

I always interested to know why people who argue that a bias toward a certain outcome makes a process non-random.

What about the short- or long-term behavior of the process (aside from the granted bias) indicates that a unbiased system in somehow distinct from all biased systems?

susu.exp wrote:I´m coming down heavily on the causal indeterminism front.
While I agree that an ontological position isn´t neccessary for science, we can still rule out some ontological positions given a particular phenomenal world. Since we can assume that there is a relation between the two and that the relation itself has to be implemented in some way in reality, we can note that a causal indeterminist phenomenal world implies a causal indeterminist reality, since you can´t use a deterministic realtion to transform a deterministic variable into a random variable (the law of large number allows the inverse transformation though, that´s why there´s only an implication, not an equivalence).

I thought you be more attune to the probabilistic causation. As I understand Pence's partial taxonomy, causal indeterminism is an epistemological position pertaining to one's knowledge of the system of interest, whereas probabilistic causation is an ontological position pertaining to the what the causal mechanism actually is.

willhud9-

I do appreciate that you took the time to give an example of how biased systems might differ from unbiased systems, but, given that one of your primary assumption is the statistical independence of events, I'm not sure how applicable it is to evolution and natural selection.

In the broadest of terms, an individual's ability to reproduce is dependent on its ability to survive until it is physically able to do so. Therefore, it doesn't seem to make much sense to me to model evolution as a series of statistically independent events.