Evolution Theory Question

Great Debates
21

Not quite. That might be true if, and only if, the shorter-necked fellow doesn’t get to mate first. Otherwise, natural selection is irrelevant - once an organism mates, it has fulfilled its evolutionary obligations. Natural selection involves the selection of those traits which, in whatever fashion, allow an organism to reproduce. It does not necessarily work for the good of the individual, but for the good of the species. Thus, we see any number of insects who mate, then immediately die. If the short-necked giraffe mutant has not had a chance to reproduce, and subsequently starves to death, then its genes will not be passed on, and the long-neck’s genes “win”.

**

Natural selection. Trees are organisms, too. Plants will evolve traits to defend themselves from being eaten, just like animals do. If it happens that taller trees have a greater tendency to spread their seeds than do the shorter ones (which might, for example, have all of their leaves eaten by giraffes, causing the tree to “starve”), then the taller trees win out.

**

Bingo! Organisms are not simply plastic objects which are molded solely by the “environment”. The organisms themselves will modify their environment, which will in turn affect the selective forces acting on them, and other organisms inhabiting the same environment, and so on. Certain outside forces, often in the form of cataclysms, can introduce massive environmental changes. In such cases, any organisms which were, through perhaps sheer chance, already capable of surviving in the new environment will survive. Those that are not so adapted will die. In some cases (and frequently throughout the history of life on earth), the changes to the environment will be so sudden and/or drastic that there will be no survivors within a given population, or, depending on the extent, entire species.

22

I think you’re referring to my calculations. Yes, they were back of the envelope calculations. I don’t know how to take into account breakdown rates of AA polymers, and I think that would make them much more complicated. It wasn’t meant to be a real scientific calculation; I only wanted to show that even a small probability of an event occurring (in this case, the formation of life) will guarantee that that event does occur given enough time and space. The reason I got 100 million years was probably due to my conservative estimate of the number of available reaction sites in the primitive sea (1 million is probably too small to be realistic).

23

By the Spirit of Wildest Bill…

**Memnojokasel Durinjio wrote:

A meteor could come and change the world climate right now. The probility for a climate changing meteor is, what every 50,000 years? And then we got global warming thats environmental changing. What I’m getting at is that on it’s own probility isn’t there but it’s always affected directly or in-directly.**

…and…

I plan on next to post a theory of mine on the possibility that there is no intelligent life forms live on any planets in “sphere of influence”. I’ll explain in the thread.

While you’re doing that, could you please learn about proof-reading and editting? The PREVIEW REPLY button is great for that! :smiley:

24

I really don’t understand what you’re saying here.

Really? Where? I keep hearing creationists refer to these calculations, yet I’ve never seen them.

25

[Hijack]

Band name!

[/Hijack]

26

Yes, yes I was. :o

27

Ben,

No. Not if there are other theories that are supported by that same evidence. Some versions of the “intelligent design” theory and some versions of the “multiple ancestors” theory are consistent with the evidence, as well.

Granted, but it was just one sentence. What did you expect?

See section 3 of my FAQ

Nice FAQ, though it seems to be as much motivated by bashing and challenging creationists as conveying factual information. Whatever trips your trigger. My philosophy is that science cannot be threatened by the ramblings of fanatics, therefore any attempt to attack wacky theories diminishes the perceived scientific maturity of the attacker. I offer this constructively…

However, the points you make in your FAQ (like the mountain of fossil evidence you mention) only support a common ancestor theory, not prove it in isolation of other theories.

Assuming that this evidence represents proof of the common ancestor theory is a logical fallacy called “Affirming the Consequent”. Here’s a common example that illustrates the problem with this kind of logic:

  • If it’s raining then the streets will be wet.
  • The streets are wet.
  • Therefore, it’s raining.

Kettlewell had good intentions, but his methods were lacking in scientific rigor that led to non valid conclusions. There’s so much wrong with that whole episode that it would be impractical to address all of the issues, but here are the big three…

Problem 1:
Kettlewell released his moths in broad daylight. Why? Because, simply, the light was better. It’s kind of like the guy who lost a quarter in the middle of the block but was looking for it at the corner under the streetlight.
So, in fact, Kettlewell’s moths congregated on the trunks of trees. Since this matched his expectation, he looked no further. However, since that time it has been shown that the natural resting place for the Peppered Moth is actually on the lower side of branches in the canopy, well sheltered from the visibility of many birds, and certainly not camouflaged by lichens or the lack of.

Problem 2:
The Peppered Moth was indigenous to many other areas, some industrialized some apparently pristine, so Kettlewell’s experiments could be easily repeated. Guess what, it was found that similar population shifts had occured in areas where the lichens on the trees were still present and no shift in alleles occured in some populations where the lichens on the trees were not present. In other words, there was a poor correlation between the coloration of the moths and the presence of lichens on trees.

Problem 3:
The conclusions of problem 2 led scientists more versed in the rigors of the scientific method to ask, “what does the coloration correlate with?” Eventually a correlation was found: Sulfur Dioxide. A very high correlation factor was found between the coloration of Peppered Moths and proximity to higher than average concentrations of sulfur dioxide or migratory paths that took them through areas of high sulfur dioxide concentrations. This theory is further supported by the observations that the ladybird beetle also exhibited signs of industrial melanism that correlated to sulfur dioxide. However, in the case of the ladybird beetles, the shift in population coloration could not be explained by selective predation, since birds avoided both color permutations.

Note: By the same argument I made earlier (Affirming the Consequent) this evidence does not prove conclusively that natural selection was not involved - only that there is no obvious connection between cryptic coloration in Peppered Moths and selective predation.

28

I can’t speak for how it works in biology or evolutionary science. However, in psychological research what we call a significant result is when the probability of finding that result by chance is very low. Most journals require an alpha level of .05, which means that that event would occur by chance less than 5% of the time. This way, we can tell if our experimental manipulations actually had any effect or if any differences were merely due to chance. I hope this helps.

29

ultrafilter:

I areee with one of your statements:

But then you followed it up with:

Using the “huge amount of time” argument to validate abiogenesis is exactly the opposite and equally invalid as the “incredibly low odds” argument in opposition to abiogenesis.

30

ultrafilter is correct, which I will explain. Let’s call p the probability that life does not appear in 1 million years, and P the probability that life does not appear in n million years. For n = 1, P = p = .98. For n = 2, P = p[sup]2[/sup] = .9604. Why is this? It’s called a conditional probability. If life did appear in the first million years, it doesn’t matter what happens in the second for our purposes, so we are only concerned when life didn’t appear in the first. So we multiply the probability this time by the total probability up to this point. So for n = 100, P = p[sup]100[/sup] = .1326, meaning that the probability that life appears at least once in 100 million years is 1 - P = .8674. For n = 1000 (1 billion years) 1 - P = .999999998.

The moral: take a probability class. Most people’s intuitive grasp of probability is not very good.

31

The existence of competing hypotheses does not mean they are all equally valid. Nor is being consistent with the evidence all that is required for an explanation. Theories involving alien agriculture can be made to fit the evidence. What is also required is testability and predictability. Common descent satisfies both of these criteria (contrary to your earlier claim that the single-ancestor hypothesis has not been tested. It is in fact, highly corroborated; indeed, moreso than any multiple-ancestor scenario). The evidence in Ben’s FAQ points to but a fraction of that available for common descent.

So-called “inteligent design” generally only comes in two flavors: one, which simply claims that since evolutionists cannot, as yet, explain every instance of complex structure and/or function in organisms, they must be wrong, and it must be the case that God (or some other “intelligence”) was responsible for their independent creation. This is, of course, simply Creationism in another guise, and precludes any notion of common descent whatsoever. The other flavor focuses on the “inherent” complexity of DNA as evidence against it arising naturally. This flavor has nothing to say about common descent one way or the other, being more concerned with abiogenesis than with ancestor-descendent relationships.

The experiment was incomplete, but the results were not unjustified. It can be concluded that the differential survival of the typica (light-colored) and carbonaria (dark-colored) versions of the Peppered Moth were most definitely a result of Natural Selection. Just maybe not in the way that Kettlewell concluded. It has not, for example, been shown that the increased survivability of the carbonaria form were attributable solely to differential bird predation on the two forms. However, other causes, such as behavioral changes in the moths, were not tested for. At best, it can be said that Kettlewell’s experiments were incomplete. To claim that the ultimate conclusion (differential survivability as a clear indicator of natural selection at work) is “wrong” is misguided and misinformed. Any differential survivability, regardless of the root cause (e.g., predation), can be attributable to natural selection.

32

True, but in this case we apparently have no differential surviveablility. Dark moths did not have better survival odds, environmental factors simply changed most of the moths into the dark form. A similar situation would occur if I spray-painted all the moths I could find bright red. You get a strong correlation between red moths and my presence, but such moths have neither a better nor worse survival rate than any other.

33

sturmhauke,

Which is exactly why claims like that ultrafilter made often go unquestioned… That and the fact that most people don’t have an intuitive grasp of very large numbers or very small numbers.

The fact is, that ultrafilter’s initial assumptions are no more justified than the ones he lambasted at the opening of that post.
Finch,

I agree, and this is not my claim. My point is that as long as there are competing theories that are equally supported by the evidence, the evidence cannot prove one theory over another.

Total bullshit. The theory is untestable, at least until we master time travel and go back to witness the event. What is testable is that tracable lines of descent are consistent with the theory. Unfortunately, there are many possible explanations that could account for the same linkage - not just the two I mentioned earlier, BTW. As for predictability… well, maybe you need to give me an example, because all of the evidence I know of involve no predictions (other than minor extensions of existing explanations). There is a big difference between explaining a connection between experimental data and a theory versus using a theory to predict a new outcome from a scientific experiment.

There are many other flavors. Perhaps I should have used the term “common design”. The implication is that maybe there are commonalities among all living things because they were put together using a common set of building blocks. Much the same as one might observe similarities in different integrated circuits from Intel or similar fragments of machine code in software from Microsoft.

The multiple ancestors theory can also be envisioned in many different ways. The simplest, leverages the arguments that ultrafilter was trying to make earlier. If the forces of nature did “conspire” to create life from non-life, then why would we assume that it happened only once? Why not a dozen times? Why not billions of times? Most of the arguments that I’ve heard to suggest that the probabilities are not as silly as creationists claim involve mechanisms that would result in many, many RNA molecules that look exactly alike or at least very similar.

Since neither the “common design” theory or the “multiple ancestors” theory requires that the original organisms are static, they are free to follow the generally accepted evolutionary tree. Possibly even intermingling to furtther increase the similarity of genetic information. This is one reason why most of the evidence in support of a common ancestor could also be used to support these alternate theories.

How is this conclusion supported? The changes in the coloration could be merely due to simple chemical changes, vitamin deficiencies, etc…

If a group of pasty faced Icelanders are relocated to Malaysia and you observe that their decendents tend to be tan rather than pink, would you conclude that this is the result of Natural Selection?
For the record, I believe that the generally accepted theory of abiogenesis is the best explanation for how life began. I believe in the common ancestor theory. I believe that Natural Selection is one of the driving forces of evolution (not necessarily the dominant one). I believe that species evolve through mutagenic and selective processes. In other words, most of my beliefs are fairly mainstream…

However, what I believe is just that: what I believe. I draw a sharp distinction between my belief systems and what I espouse as fact. I recognize the limitations of the data at our disposal and our abilities to interpret that data accurately. It is the duty of all competent scientists to recognize these limitations, otherwise we lose our objectivity and we may overlook relevant results simply because they don’t match our expectations or we may find correlations where there are none.
One of my favorite quotes from Sir Karl Popper captures my point quite poignantly:

34

I’m curious why you think my assumptions are bad. Please explain.

35

Not exactly.

Here is a great article on the issue.

36

ultrafilter,

I didn’t say “bad”, I said “unjustified”. However, since you seem to be taking a defensive stance, perhaps I have spoken out of turn. Why don’t you explain your justifications and if you can convince me that your assumptions are sound, then I’ll print a retraction.

Let’s start with:

I agree that this seems like an incredibly small number, but is it small enough? Aside from the obvious fact that life did “apparently” emerge, how do you know that the probability is not zero (or at least much more near to zero)? Also, just curious, why did you choose something that looks suspiciously like Avogadro’s Number with a twist? Was this some bastardization of a mole?

BTW, the probability assumption at talkorigins is 2.33 * 10[sup]-41[/sup], but this too is based on a lot of unsubstantiated assumptions…

Interesting assumption. Many experts disagree. See the Abiogenesis FAQ at:

http://www.talkorigins.org/faqs/faq-abiogenesis.html

This expert, like many others, suggests that life originated by catalyzing on crystaline structures on clay in small ponds or lagoons. He concludes:

I tend to agree that this has a higher probability and it has a certain structural elegance that appeals to my sensibilities.

Onward…

I can’t even guess what you pulled this number out of.

The bottom line is that I think there are too many assumptions that have to be made: Which model of the early Earth do we assume (frozen, modern, or hot)? Do we assume a Hydrogen, Methane, and Ammonia atmosphere as Stanley Miller did, which produces a wealth of amino acids when zapped or do we assume a predominantly Carbon Dioxide and Nitrogen atmosphere as many scientists now believe and which greatly reduces the avaliable raw materials? Do we assume a google of organics floating aimlessly in the oceans, only to combine through random forces or do we assume the tidal pool theory which adds structure, but greatly reduces the number of reaction sites and lengthens the reaction cycle time. Was the first proto-organism a replicating RNA molecule or protein? Blah, blah, blah…

I could go on asking such questions for a long time, but it would not serve the point significantly, other than to paint a grimmer picture for the hopes of using probabilitiy calculations to prove anything about abiogenesis…

37

All of the objections you raise are very likely valid. My calculation for the number of independent reaction sites was 1 million (the number of spatial locations) multiplied by the number of seconds per year (the number of temporal locations). These were not meant to be scientific calculations; rather, I just wanted to show that, even if there is some astronomically small chance of abiogenesis, it’s very likely to happen given enough time and space.

The 6.02 * 10[sup]-23[/sup] was just the first thing that popped into my head, since I didn’t feel like looking up any particular estimate. The specific value wasn’t really important for my point, I thought.

Well, I’m assuming it’s nonzero because even the creationists think so. It could be zero, but the only way I would accept that is if someone were to show that abiogenesis is absolutely impossible given the conditions of the primitive earth. You’ll have to pardon me if I’m not going to hold my breath waiting for that to happen.

As for the number of assumptions, yeah, the situation is not well-known enough to make any specific model. I tried to pick a simple one that would be easy to follow.

Again, the point I was trying to make is that astronomically small probabilities of an event happening actually imply that it’s very likely to happen in the long run. Does my example seem like it succeeds at doing this?

38

OK, I went back into my stochastics book and looked up some stuff. There is a way to model this, but it’s really complicated, and it would require way more assumptions than my previous calculations. So I’m gonna go ahead and not do those, if no one minds. :wink:

39

CheapBastid,

I’m not sure what you’re arguing. Se seem to be disagreeing with Gaspode’s statement:

But then you post a url that supports that line of thinking… I’m not getting your point, me thinkst .
I do want to thank you though because this site makes reference to an experiment that I’ve never heard of:

The theory of induction was later rejected and apparently not investigated further, not because it was necessarily unsound, but apparently because it was not consistent with and didn’t support the prevailing theory (read popular theory of the scientific masses) of Natural Selection. This is exactly the kind of “wrong science” that Popper warned of, “craving to be right”.

40

ultrafilter,

Not at all. Hardcore creationists think the probability of abiogenesis is exactly zero. They require the hand of God to perform a miraculous act. Average Christians are a bit more forgiving in that they allow for the minute probabilities and believe that God either influences things on a micro-cosmic scale or he made the probabilities whatever they were such that it would happen.

No I think you’re missing my point. Let’s carry your assumption to it’s logical conclusion. Assume that the probability of an event happening is zero, but the time that you’re willing to wait for this event to happen is infinity. So what’s the probability of the event?

How close to zero is the probability of abiogenesis??? We simply don’t know. It might be very close. It might be much closer to unity than we might guess. It might be very, very close to zero, yet still could have happened. Probability doesn’t tell you what will occur, merely what you can expect from a reasonably large population of trials.

How close to infinity is the available time period involved??? Well, we actually have a pretty good guess about that - somewhere between 300 and 500 million years after the Earth was born… which is much less than infinity.