Evolution is a non-random directed process

Creationism, Evolution, and other science issues

Moderator: Moderators

User avatar
ProfMoriarty
Student
Posts: 26
Joined: Sun Oct 10, 2004 7:35 am
Location: (near) Bristol, England
Contact:

Evolution is a non-random directed process

Post #1

Post by ProfMoriarty »

The notion of Intelligent Design is often raised as a potentially acceptable alternative to evolution. The claim is often made based upon the following supposition:

– evolution is a random process, so how could it have produced the complex organisms we see today - but an Intelligent Designer could have intervened and directed evolution to produce all the world's creatures and man.

However, evolution is not a random process.

The issue I want to raise for discussion is:

"Darwinian evolution is a non-random directed process. "

This is strictly in accord with both Darwin's original discussions in On The Origin Of Species, and also with current evolutionary theory, and is what enables evolutionary theory to be able to explain adaptive change and speciation.
Prof M

Evolution is just a theory, and proud of it. :idea:
THE BRIGHTS - http://www.the-brights.net/fourms

User avatar
Jose
Guru
Posts: 2011
Joined: Thu Sep 02, 2004 4:08 pm
Location: Indiana

Post #2

Post by Jose »

Good idea!

Exactly so: selection (whether by environmental factors or by humans engaged in selective breeding programs) is non-random.

I built a simulation of this concept some time ago, designed for low-tech situations. Somewhere on the web is a high-tech version of it. It illustrates how different types of selection pressure can give rise to different outcomes, even with the same starting material.

User avatar
ProfMoriarty
Student
Posts: 26
Joined: Sun Oct 10, 2004 7:35 am
Location: (near) Bristol, England
Contact:

Post #3

Post by ProfMoriarty »

So far no one has picked up on this from either So far no one has picked up on this from either side of the debate; which I find a bit surprising seeing as the notion that Darwinian evolution is a non-random directed process should have raised a few eyebrows, as it appears to go against the accepted wisdom from both sides.

When I use the word "directed", I don't at all mean by that term that God or any other intelligence has anything to do with it. Nevertheless, evolution by natural selection is undoubtedly directed by various factors to produce optimal adaptation for the prevailing environmental conditions. This one simple fact goes a long way to being the main reason why evolution can perfectly well explain the development of life on earth over the last 4.5 billion years. It also explains how speciation can occur given adequate time and the necessary conditions.

The creationist scenario really has no counter for this fact within evolutionary theory, as the arguments against evolution tend to be based on the assumption that Darwinian evolution is a random and undirected process which, if that were true, cannot be expected to produce complex lifeforms. The fact that it is non-random and it is directed by natural selection undermines this assumption completely.

Does everyone already agree with this? Can we therefore take it that creationism accepts that evolution is the means by which life has reached it's current state?
Prof M

Evolution is just a theory, and proud of it. :idea:
THE BRIGHTS - http://www.the-brights.net/fourms

User avatar
ENIGMA
Sage
Posts: 580
Joined: Thu Jun 24, 2004 1:51 am
Location: Atlanta, GA

Post #4

Post by ENIGMA »

*takes this opportunity to point out the weasel applet*

(Not to be confused with the badger movie)

:)
Gilt and Vetinari shared a look. It said: While I loathe you and all of your personal philosophy to a depth unplummable by any line, I will credit you at least with not being Crispin Horsefry [The big loud idiot in the room].

-Going Postal, Discworld

User avatar
Jose
Guru
Posts: 2011
Joined: Thu Sep 02, 2004 4:08 pm
Location: Indiana

Post #5

Post by Jose »

ProfMoriarty wrote:Does everyone already agree with this? Can we therefore take it that creationism accepts that evolution is the means by which life has reached it's current state?
This is a good nudge. Maybe it will get some discussion going. It's an interesting thing, as you note, that we haven't seen any objections. Usually, it's the presumed randomness that makes creationists so concerned. You know--the whirlwind in the junkyard argument. We'll see what happens next...

User avatar
otseng
Savant
Posts: 18629
Joined: Thu Jan 15, 2004 1:16 pm
Location: Atlanta, GA
Has thanked: 147 times
Been thanked: 229 times
Contact:

Re: Evolution is a non-random directed process

Post #6

Post by otseng »

ProfMoriarty wrote: "Darwinian evolution is a non-random directed process. "

Does everyone already agree with this? Can we therefore take it that creationism accepts that evolution is the means by which life has reached it's current state?
OK, you nudged me. ;)

Darwinian evolution as I understand it is a two step process - mutation and selection. Though I might accept that the selection step is "directional", the mutation step is clearly random and non-directed. It is this step that is the most problematic. Can mutations account for the generation of all biological diversity? I would argue no.

So, though the step 2 might be "directed" and "non-random", step 1 as I understand it is not.

I would be curious as to how other evolutionary proponents think of this notion that evolution is "non-random and directed". (Just trying to nudge others also)

User avatar
Jose
Guru
Posts: 2011
Joined: Thu Sep 02, 2004 4:08 pm
Location: Indiana

Post #7

Post by Jose »

otseng wrote: Though I might accept that the selection step is "directional", the mutation step is clearly random and non-directed. It is this step that is the most problematic. Can mutations account for the generation of all biological diversity? I would argue no.
Take a peek at the simulation I mentioned earlier. You don't have to do it, because there are links to a couple of filled-in sheets. If you read the "rules," you'll see that mutation is random. All that changes is the "selection pressure." This should provide a glimpse into the mechanism: even with random mutation, selection can give rise to apparently-designed outcomes.

Whether you accept that this mechanism can account for all of biological diversity is, perhaps, another matter. Let's start with something simple, like the simulation, and see if in principle the concept is acceptable. Note that this is an issue of microevolution--changing allele frequencies--and can therefore be accepted as a means of change within kind.

User avatar
ProfMoriarty
Student
Posts: 26
Joined: Sun Oct 10, 2004 7:35 am
Location: (near) Bristol, England
Contact:

Post #8

Post by ProfMoriarty »

I'll get around to the details of this but it requires a bit of thought. However, the general concept is this:

1) we are only discussing evolution by natural select at this point. Evolutionary change through nuetral drift and other non-selective effects is not directed.

2) Natural selection can only have an effect when there are variations at a genetic level within the local population. Variation is caused by changes in the combinations of genes, or by mutation, within the parental gametes which are then inherited by the offspring. Organisms do not mutate, gametes mutate. Individuals do not evolve, populations evolve.

3) Genetic variation through mutation is always random - mutation is not directed and evolutionary theory explicitly excludes such a concept. Selection cannot therefore directly influence or dictate mutation.

4) I have to introduce at this point the concept of the adaptive landscape (proposed by Wright, 1963). This is the concept that there are many optimal adaptive schemes for a set of genes, and these could be drawn as a multidimensional graph which would appear similar to a landscape. Each point on the landscape would represent a combination of genes plotted against the relative adaptive fitness of those genes. Combinations that represented better adaptation would appear as peaks, and ones with low adapative fitness would look like valleys.

5) Using a simple combination of 4 linked genes as an example it is easy to see how this works. Genes exist as alleles, which are alternative versions of a gene. In this example, by convention genes for +ve adaptive value are represented by uppercase letters, and -ve by lower case. So the 4 genes would be A, B, C, D with homologues of a, b, c, d. As both versions of the gene must be retained by the population, it is common for such groups of genes to be linked, which means that during meiosis they would normally cross over together. The optimal combination in reality is for all members of a population to have 50% +ve alleles 50% -ve within the gene, and for 50% of the population to have, for example ABcd, and the other 50% abCD. This gives the optimal adaptation without losing any capability for variation. A, B etc. do not represent a specific gene, they merely represent the most adaptively useful allele for the current environment. In a different environment the same allele could well have a -ve adaptative effect.

6) So, on the adaptive lanscape the lowest valley would represent alleles abcd, and the highest peak ABCD, but in reality the most optimal is going to be ABcd or similar.

7) At each generation, recombination and mutation will affect these genes and create offspring covering positions within the range from least adaptive - abcd, to most adaptive, ABCD. On our lanscape these would represent various points within the graph. However, because mutation etc. is very slow, the actual range will be only slightly -ve to slightly +ve in relation to the parental population. You can picture the parents as a point on the landscape and the offspring as a spherical cloud around that point.

8.) Direction is imposed by natural selection. Natural selection directs adaptive change. Because the combinations with higher values (more capital letters) are better adapted, offspring with these will have a higher chance of reaching reproductive age and having offspring of their own. The less well adapted (more lower case letters) will correspondinly tend to reproduce less. This is where selection directs adaptation and indirectly influences the mutation of the genes. In this example, the parent was a point on our landscape graph, and the offspring more points in a cloud around it - however the points closer to the optimal value will be able to reproduce more than those further from it, and so the cloud of points, generation by generation, will move slowly towards the point of optimal adaptation (abCD or whatever). Mutation is still entirely random as required by the theory, but the starting point for the random mutation is shifting by generation - so indirectly natural selection preferentially supports mutation towards the optimal point while suppressing it away from that point. Once the optimal genetic combination has been reached, for as long as environmental conditions remain stable, natural selection will then stabilie the adaptive change to keep it within the adaptive optimum.

9) So, basically, Darwinian evolution is a non-random process directed by natural selection. This is at total odds with the erroneous concept that evolution is random - the only part which is random is mutation, and that is specifically required by natural selection, otherwise there would be no variation for it to work upon. The adaptive change is not at all random, as selection will always drive gene combinations in the direction of the best adaptive fit for the environment. It is worth noting that this is all perfectly standard evolutionary theory and can be checked in reference books - I wrote this from memory so you might find a few things I got wrong, in which case the textbook is the correct one! The reference I use is Strickberger's "Evolution".

10) For speciation to occur it is usually necessary for some sort of split off from the local popultion to occur. For instance, allopatric speciation requires that a sub-population is cut off from the main population by some sort of geological or other physical barrier. This could be a river, distance, predators, etc. The founder effect comes into play here because the sub-population will have a limited number of gene combinations available to it as compared to the main population. So selection will quickly try to direct adaptive change based upon these limited combinations. For speciation to occur all that is required is for the genetic complement of the two populations to diverge sufficiently that the are unable to reproduce, or are unable to produce viable offspring, or choose not to interbreed. This isolates the two gene pools and enforces further divergence which is not reversible.

Evolution in this respect is confirmed by vast amounts of evidence from every branch of biology - from paleaontology to genetics. However it really is at odds only with a literal form of creationism which relies on assumptions that cannot be supported by the evidence available. If on the other hand someone wants to assume that God used evolution to bring about the current forms of life on earth they are perfectly free to do so. This would be a form of intelligent design, which although not required at all by evolutionary theory, does at least understand that evolution is a fact which cannot be ignored. Many christians hold this view, and I have no problem with it although I can see some serious philosophical implications which result from it.

I hope that describes the basics of what my argument is. It really needs a few diagrams to make it clear, but as I said this is all in the reference books so it is easy to confirm. It should make it clearer how evolution actually works.
Prof M

Evolution is just a theory, and proud of it. :idea:
THE BRIGHTS - http://www.the-brights.net/fourms

User avatar
otseng
Savant
Posts: 18629
Joined: Thu Jan 15, 2004 1:16 pm
Location: Atlanta, GA
Has thanked: 147 times
Been thanked: 229 times
Contact:

Post #9

Post by otseng »

ProfMoriarty wrote:3) Genetic variation through mutation is always random - mutation is not directed and evolutionary theory explicitly excludes such a concept. Selection cannot therefore directly influence or dictate mutation.

If genetic variation is random, I cannot see how evolution then can be non-random.

Mathematically, if x is random, then f(x,y) would also be random.

How can it be shown that the entire process of Darwinian evolution is non-random given that mutations are random?
The adaptive change is not at all random, as selection will always drive gene combinations in the direction of the best adaptive fit for the environment.
However, you stated that "selection cannot therefore directly influence or dictate mutation." Selection should not be able to affect in any way gene mutations/combinations. It can only choose from the resultant genes that were produced.

User avatar
ENIGMA
Sage
Posts: 580
Joined: Thu Jun 24, 2004 1:51 am
Location: Atlanta, GA

Post #10

Post by ENIGMA »

otseng wrote:
ProfMoriarty wrote:3) Genetic variation through mutation is always random - mutation is not directed and evolutionary theory explicitly excludes such a concept. Selection cannot therefore directly influence or dictate mutation.

If genetic variation is random, I cannot see how evolution then can be non-random.

Mathematically, if x is random, then f(x,y) would also be random.
I have a counterexample to that claim:

f(x, y) = A(y) such that

A(0)=x
and
A(n+1) = A(n) + sin(A(n))

For sufficiently large y (Infinite is ideal, but 10 or so is often sufficient for a close enough approximation), and 0<x<2*Pi (6.28....)

f(x. y) = Pi (3.14159...)

Now, the time it takes for the algorithm above to iterate to Pi is dependant on the initial value of x (i.e. If some arse was to set x to be .00000000001, then it would take a few more iterations.) However the final result is the same regardless of the initial x that is input into the function. Feel free to try it out at your leisure.

Please note that being able to discover random mathematical stuff like this is a benefit of being bored in AP Calculus and having a Casio graphing calculator, which does not play games. ;)
Gilt and Vetinari shared a look. It said: While I loathe you and all of your personal philosophy to a depth unplummable by any line, I will credit you at least with not being Crispin Horsefry [The big loud idiot in the room].

-Going Postal, Discworld

Post Reply