Evolution 101

Sunday, August 13, 2006

What is Information Theory?

I received some feedback from David regarding the discussion of human nudity from last week that I thought was relevant. In addition to the explanations which I gave regarding the presence of pubic hair, he mentioned that it also functions to retain the body odors produced by the apocrine glands located in and around our genitals. These odors are relevant to sexual signaling even today, it has been reported that men can tell by sense of smell when women are the most fertile. So an additional selective pressure to retain pubic hair even as humans lost hair over the rest of our bodies, was to preserve this sex-related scent, since the presence of hair prevents secretions from evaporating quickly.

Frank writes to ask:
Can human inventions, such as the car, influence evolution? For example, if enough deer get hit by cars, and there is a tiny percentage that run away from headlights, (instead of staring into them), is it possible that some day very few deer would ever be hit by cars?

It certainly is possible for humans to influence evolutionary development, since evolution is dependent on the selective pressures of a populations’ environment, and humans are a part of the environment. This is especially evident when you look at the development of domesticated animals and plants- almost always vastly different from their closest-related wild relatives. But domestication is a kind of an accelerated evolutionary adaptation, since intentional breeding patterns are set up in just about every generation. For organisms that are still outside of direct human control, like deer, changes would be much longer in development, if at all. In the example you gave, I doubt that there would be much of a trend away from being hit by cars, since the genetic causes of that behavior are very complex. In addition, you want to look at the specific behavior in question. If there is enough of an advantage to that behavior to offset any disadvantage, then it’s unlikely that you would see a dramatic reduction. Here, the tendency of deer to cross large swaths of territory in search of food and shelter necessitates their crossing of roads. It’s conceivable that if there was a large enough disparity in the number of deer hit and killed versus those deer that successfully crossed roads, there might be enough environmental pressure to select for the best crossers, but the deer population is large enough and the percentage killed this way is small enough that I doubt this would happen.

Jason writes in to tell us,
“Apparently, there has been some research of homosexuality being potentially created by Neanderthals, who then engaged with homo erectus in sex and spread this gay disease to current man. Honestly, I've read conflicted interest on whether or not Neanderthals could have sex or even breed with homo erectus. But in the event this was true, could the changes even last this long, or affected enough people to make it a modern day problem? Fox News recently had an article of the US Government arguing how homosexuality is a mental condition, a "disease" that can be cured someday.”

First of all, homosexuality is not an infectious disease. You can’t “catch” homosexuality. Homo neanderthalensis was a prehistoric hominid, but was not a direct ancestor of modern humans. It is possible that some sexual contact between our ancestors and Neanderthals took place, but if it was it was infrequent enough not to make any impact on our genetics. Certainly homosexual contact between the two would have had no impact on our genetics whatsoever. I am aware of the classification by the United States Department of Defense citing homosexuality as an example of a mental disorder, but this seems to be just a holdover from decades ago, when this was actually the majority view. Whatever their reason for doing so, I can guarantee this has nothing to do with Neanderthal gay sex.

Brad asks:
“is the wide range of intelligence in the human species similar to what you would find in other higher mammals? I realize that intelligence levels often are reflected in the social aspects of a person...are some monkeys clearly smarter than others...do some monkeys "live" in higher-class places?”

Well, although this is a really interesting question, I don’t think that there’s much in the way of “higher-class” accommodations in the jungle. But in recent years there has been growing support for something called the Machiavellian Intelligence Hypothesis, which suggests that intelligence evolved in our ancestors as a way to better adapt to the complexities of the social order. That is, in order to keep track of social relationships and how to make the most advantage of them, essentially “playing politics,” higher intelligence was selected for. In primates of nearly all species, excluding non-social species like the orangutan, we would expect the most “intelligent” members of their population to also be the most socially cunning, and would likely be the ones with the most social power. This phenomenon is also seen quite often in the human species, as embodied by the phrase, “It’s not what you know, it’s who you know.”

Jordan asks:
“A friend of mine is wondering about mimics (in biology). I explained the basic natural selection process to him - how, if a certain physical characteristic proved reproductively beneficial that it would become more frequent, etc. But he's stuck on the "what are the odds" question, and I'm not sure how to get past that. In his example, there's an island with poisonous snakes on it that are black with yellow stripes. There's also a worm that has developed the same coloration in order to avoid becoming prey. How does this happen?”

Just think about the selective forces at work here. A classic example of mimicry is the Monarch and Viceroy butterflies. The monarch caterpillar feeds on milkweed and thus the later butterfly is bitter-tasting. The viceroy does not feed on milkweed, and thus tastes quite normal. However, both butterflies appear very similar in terms of coloration and marking. Consider this: predators experience the bitter taste of the monarch, remember its coloration, and avoid killing further monarch butterflies. Since the avoidance is based on that particular visual imagery, any other butterflies that happen to look similar to it (like the viceroy) would also be avoided by the predator, since they evoke the same visual imagery. Any members of the viceroy population that happen to look significantly different from the monarch would not evoke this avoidance, and would be eaten at the same rate as other non-bitter butterflies. Thus, the only viceroys that remain to breed are those that look more like monarchs. Over time, this mimicry was amplified, to the point where it is today. This is classic natural selection in action- and a phenomenon that is predicted by evolutionary theory.

And finally, some criticism from Susan:
“Hey, I just thought that I would say that I really thought that I would like this podcast, I believe in evolution and am very well read in evolution. But after listening too quite a few podcasts, I couldn't stand it anymore, I had to delete it. You see I believe in evolution, but I am also a Christian and couldn't take the bashing every minute in the podcast, I loved the information, but I couldn't take the slamming anymore. You see, I find no problem with believing in evolution and believing in God. I know that there are creationists that may be very outspoken with their beliefs or rather disbelief in evolution, but to say that everyone that believes in God does not believe in evolution and is uneducated in the area of evolution is a very ignorant statement. Also the conclusion that was made of the correlation between creationists and intelligent design is not true, I do not believe in intelligent design because you cannot rationalize God, because God is not science, God is a belief, so to try and put God in boundaries of science would not be true. Listening to the podcast did not teach me anything about evolution, but did teach me about how someone who is so smart in one area can be so ignorant and uninformed on another. Take for example Francis Collins, the director of the Human Genome Project, he is a Christian, but also is a Christian. You slam creationists, believing that creationism is all wrong, but what you don't mention is that evolution also has things that have been changed and holes that are still present in evolutionary theory. For a well educated person, you are very narrow minded.”

Well Susan, I’m sorry that you feel I’m bashing you, but I have never said that “everyone that believes in God does not believe in evolution.” In fact, I’ve tried to make it very clear that there are many Christians that do! Ken Miller, as I’ve mentioned before on this podcast, is a Catholic and evolutionary biologist who has written the excellent book “Finding Darwin’s God,” which is an excellent resource for anyone seeking to learn more about evolution, and especially for those who want to resolve evolution and the Christian faith. If you didn’t learn anything about evolution from this podcast, you might want to check out this book, written by a fellow Christian who believes that creationism is wrong and evolutionary theory is the only scientific explanation.

Today I want to get back to one of the questions that was posted on the old site. Grelnixar asked,
“What exactly are “information” in a pure biological sense? When speaking to creationists I often encounter analogies to digital information (which always require a designer(s)) but how accurate are these analogies? Can you give an example of observed positive genetic-information increase.”

This is an excellent question, and it’s getting at one of the common objections to evolutionary theory, which goes something like this: For evolution to take place, the genome of a species must become more complex. An increase in complexity requires an increase in information, and according to information theory, random mutations cannot increase information. Therefore, evolutionary theory cannot be true. This objection is frequently made by those who are advocates of “intelligent design,” and particularly one William Dembski, who considers himself one of the front-line experts of information theory as it relates to evolution.

Any time you see one of these objections which refer to “information,” genetic or not, especially in reference to this “information” either increasing or decreasing, there’s a good bit of underlying assumption behind it, which is usually unknown to the objector. This underlying assumption is that information theory directly interacts with evolutionary theory. The short answer is that information theory is relevant to evolutionary theory, but not in the way that is intended by the objection. Unfortunately, that’s the best answer that my expertise can provide, because information theory is well beyond my training and understanding. To get to the long answer, I’ve asked a good friend of mine and mathematical expert to explain what “information theory” is in the first place, and how it relates to evolution. I’ll yield the floor to him.


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