novembro 25, 2009

A Few Question on Evolution

Este é um copy-paste do blog NeuroLogicaBlog escrito pelo Steve Novella, que contém diversos pontos interessantes sobre erros nas argumentações dos anti-evolucionistas.

Evolution and its pseudoscientific denial is a topic that comes up often on this blog. The comments to those posts, as well as e-mails resulting from my podcast, provide good fodder for discussion. I also think that confronting misconceptions is a very effective way to teach science, because it invariably involves exploring logic, evidence, and how we know what we know.

Here are a few recent tidbits I thought I would weave into a post.

Punctuated Equilibrium

SGU listener Michael Morrison e-mailed me about a discussion with his uncle, stating:

He stated that many scientists believe that there is not enough time in the history of the world for the current complexity of life to have developed through evolution. He stated that this problem was the impetus for developing the punctuated equilibrium theory and was just another example of scientists trying to explain away God. He referenced Frances Crick and his alien seed hypothesis as proof that even noted scientists recognize that lack of time is a problem for the theory of Evolution.

First, let me correct the misconception about punctuated equilibrium (PE) – it has absolutely nothing to do with there being enough time for evolution to have occurred. PE was developed by Gould and Eldridge to explain the apparent stability of species in the fossil record. Species do not constantly change, as Darwin surmised, but rather remain at rough equilibrium with their environment, punctuated by relatively rapid speciation or extinction events.

What PE means is that evolutionary changes tend to be compressed into short bursts, rather than occurring constantly and uniformly throughout nature. In the decades since the 1972 publication of PE, much evidence has emerged to support it, but also to show that there is no one mode or pace to evolution. Slow change also occurs within many species. [...]

Time Enough for Evolution

But let’s get to the core question here – has there been enough time for evolution to have occurred. Well, three plus billion years for all life on earth and 600 million years for multi-cellular life is an awfully long time. But is it enough?

Here is one of the better examples of this argument, from Laurence Smart, author of Unmasking Evolution. He makes a calculation concluding that there has not been enough time for an ape to have evolved into a human. Smart is an educator, but not an evolutionary biologist, and he displays multiple misunderstandings of evolutionary theory – but I will focus on this one argument.

His calculations are based upon a number of absurd assumptions. First, that all mutations are point mutations – one nucleotide changing at a time. Second, that it takes 300 generations for a new mutated form of a gene (allele) to completely replace the previous gene allele. And third, that only one mutation can be selected for at a time. None of these assumptions are well founded.

There are multiple mechanisms of genetic change, including those that involve entire genes or even entire chromosomes.The “one nucleotide at a time” assumption is patently false. Here is a list:

  • Endosymbiosis
  • Whole genome duplication (polyploidy)
  • Chromosomal rearrangements
  • Gene duplication
  • Hybridization
  • Gene displacement
  • Horizontal gene transfer
  • Jumping genes
  • Sexual recombination
  • Retrotransposons (Alu sequences)
  • Exon shuffling and domain exchange
  • Repetitious DNA and repetitious peptides

Further, there is no reason to assume one change at a time. Suites of mutations may be selected for, and there can be multiple overlapping selective processes happening at the same time. There is also no reason to assume that one mutation must reach 100% replacement before the next mutation can be selected for.

Further, Smart assumed a population of 100,000 individuals. The evidence suggests, however, that our ancestors passed through a time when the population was restricted to about 2,000 individuals. The smaller the population, the more quickly a new mutation can dominate the population. And in fact it is likely that most speciation events take place in small isolated populations.

So Smart’s calculations are worthless, and in the end there is no legitimate line of argument or evidence to suggest that there has not been enough time for evolution to have occurred.

I will add that if this were true – that current calculations show there has not been enough time for the evolutionary changes we observe to have occurred – this would not be evolution’s “dirty little secret” but rather a major focus of research. Scientists love when something does not fit, because it means we have a false assumption, which further means there is a major discovery waiting to be made. Evolutionary scientists are not tripping over themselves to solve this apparent anomaly, because it does not exist.

Evolution as a Designing Force

Commenter Sylvester left a rather incoherent comment on an older post, so I will reply here. He wrote (quotes are from my original post):

“Evolution is a designing force”= Who or What, and where is that force coming from?

“it has been shown that complex information can emerge spontaneously out of blind”= Out of blind??? wow! That sounds lke magic. Sorry but there is not hard evidence to support such claim.

This seems to be a real sticking point for most evolution-deniers – the notion that complexity can spontaneously emerge out of simple processes. Like Sylvester, they make what amounts to an argument from personal incredulity combined with a simple denial of evidence.

We talk of “forces” and “pressure” in evolution, but the terms are not meant to refer to physical forces – they are metaphors for evolutionary processes. An environmental condition can produce a “selective pressure” – meaning that there will be differential survival in a population (as opposed to random survival). Differential survival results in changing gene frequencies over time.

This is an internal process. Sylvester seems to think (I have to infer, as his comments are almost devoid of specifics) that by using the term “creative force” I was implying an outside force – I was not.


He continues:

“If you start with one version of a gene and then it mutates in one offspring but not in another – now you have two versions of that gene. That represents an increase in information”= Not at all. Duplication of information is not an Increment of information. You are misusing the meaning of this word. To increase information is to obtain more complex information from previous information sources. Not duplication.

Sylvester misunderstood my point and misunderstands the concept of “information” – as do Intelligent Design proponents. First, I did not say that the mere duplication of the gene results in an increase in information. Rather, I very specifically said that the duplication followed by differential mutations results in increased information – because now we have two different versions of the gene, where there was one version before.

That is, by definition, more information. It would take more information to completely describe the two genes that it would their single parent gene. Sylvester simply missed what I wrote.

But further he then equates information to complexity – another common mistake of the ID crowd. Information has a mathematical meaning, and it has nothing to do with complexity. In fact, randomness can be very information dense.

The now common example is to take a Word document with 1000 random characters, 1000 letter As repeated, and an essay with 1000 characters. If you then compressed these three documents (compression is the process of representing the document with the least amount of information possible) you will find that the random characters has the most “information” from a mathematical point of view – it does not compress as much as the other two.

This may seem counterintuitive, but it comes from using a sloppy definition of “information”, or casually switching among several operational definitions of “information.”

But, no matter how you slice it, two different genes is more information than either gene alone.


He then finishes with this point:

“there is nothing in thermodynamics that states that the Earth cannot use energy to create a local decrease in entropy.”= Perhaps a local decrease in enthropy but increasing the overall enthropy elsewhere. It seems like is a hard concept for you to digest. You still do not get it.

Huh? I am not even sure what he is saying here. My original point is that the decreasing entropy (or increasing complexity, order or information – however you want to say it) in the biosphere over time does not violate the laws of thermodynamics, as many evolution deniers still amazingly contend. This is because the earth is receiving energy, and that the process of life uses that energy to do work, and the result of that work can be a decrease in entropy.

Put another way, the earth is not a closed system – it is an open system receiving energy. Thermodynamics only states that in a closed system (not receiving energy) entropy must increase.

Earth’s local decrease in entropy is more than offset by increases in entropy elsewhere in the universe – for example in our own sun, which is increasing its entropy as it spews out energy.

What creationists are essentially saying is that (for example) an electric train cannot run by itself without an energy source, therefore the train is not running. Despite evidence that the train is in fact running, I can also point out that the tracks are plugged into the wall where they are receiving a steady 220 volts and using that electricity to run the electric trains. Sylvester’s response to this is typically incoherent. (And of course the irony of his final sentence is classic.)


Readers might think I am being unfair picking on Sylvester and Michael’s uncle – but their questions really are typical of the average creationist. In fact (although not as verbose or eloquent) this is typical of the best arguments from the leading lights of creationism and ID.

Creationist arguments are logically flawed, factually challenged, and often border on incoherent. What is worse, you can make a very plain and straightforward argument and they will often find someway to misinterpret it.

In fact I predict that very statement will be misinterpreted as an ad hominem against creationists, even though I specifically wrote “creationist arguments.”

But they are amusing, and can be a very useful tool for improving the public understanding of science.

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