Evolution 101

Sunday, July 16, 2006

Miscellanea

I was interviewed this week for the Biota.org podcast, which focuses on the development of artificial life models. This field is of interest to evolution, because these models can be wonderful experimental tools to test out specific components of evolutionary theory without having to wait for hundreds of thousands of years, and they can also be great educational tools. One fun artificial life program that I’d recommend for you to check out is called, “Gene Pool,” and it can be found at www.ventrella.com. At any rate, check out the Biota.org podcast if you’d like to hear that interview.

This podcast is growing in popularity, and I’m getting more and more questions emailed to me. This is great, and I would encourage anyone who has a question to send it in, and I might even answer it on this podcast! This week, I’m not going to have a specific topic, and instead I’m going to respond to as many emailed questions as I can.

The first question is from Mark, although I received several similar emails from other people asking about a comment I made in response to an email that I answered last week. He writes:

You mentioned in the podcast that, although you are an atheist, you spend your Sundays in church. That was a little surprising, though not a lot. I continued to attend church for a few years after rejecting religion, I suppose out of habbit and for socialization. I was just curious as to why you continue to do so and whether you find yourself in situations where your scientific knowledge is in direct conflict with church lessons or issues.

Well, I’m sure that the idea of an atheist attending church seems a little strange to some people, but it’s a unique situation. I visit with a specific group at the church that examines issues that most people regard as being in opposition to religion, such as evolution. I go there every week, partially because I like interacting with the people there, and also so that I can provide accurate information about things like evolution that people there wouldn’t be aware of. You might think of it like an Evolution 101 house call, or church call, more accurately.

The next question is from Eddy, who writes:

macro and micro evolution When using terms like these it is hard to say that there is no difference between the two.... Dr. Raoul A. Robinson defines a difference between macro and micro evolution. Two distinctions he makes are: - timescale, some changes can occur in relatively short period of time (decades to millenia) - persistence, some change occur, but can be changed back... Does this makes sense?

Well, Eddy, I touched on micro and macro evolution back in podcast 102, where I looked at examples of what evolution is not. Dr. Robinson is correct in that, typically we think of microevolution occurring over a short period of time. However, the best distinction that could be made is that microevolution is that which does not change one species into another, and macroevolution is that which changes one species into another. But the only difference here is timescale, not mechanism. The same mechanism that causes an organism to gain a single trait is the same mechanism that causes a new population to speciate from another. We’re only talking in difference of scale. As a comparison, think of a garden hose- turn the water on high, point it at the ground, and within a few minutes you’ve cleared out a good-sized rut in the dirt. Nothing too special- that’s the force of erosion at work. But instead of running it for ten minutes, what if you run it for ten years. How big a rut do you think it would be then? What about ten thousand years? Now you’re getting a sense of the difference in timescale between micro and macroevolution. Or you can think about economics. Do you think that the five dollars you spend at Wendy’s to buy a chicken sandwich affects the amount of money the store makes in a day? Of course it does. What about the millions of customers ordering chicken sandwiches around the world- does that affect the multimillion dollar deal they make with an advertising company? Of course it does- same mechanism (people buying chicken sandwiches), just an increase in scale. Remember that the next time anyone tries to use micro and macroevolution as a way to deny evolutionary theory.

The next question is from James. He writes:

All my life (almost 54 years now), I have heard statements regarding the evolution (in humans) of a larger brain being significant; that evolving a larger brain is what made us more intelligent (whatever that is) than other animals. So, my thoughts are: Elephants have larger brains than humans. Why aren't they more intelligent than us? I believe some whales also have brains larger than humans. The average man has a bigger head than the average woman, but women and men seem to be equal in intelligence; some people have tiny heads, but are very smart, while others have large heads, and are quite stupid. My hypothesis is that brain size is insignificant (beyond a certain point). It must be how the brain is organized that really matters. Brain structure, along with proper wiring or programming (a.k.a. experience), is what makes the difference, not the size. Am I right? And if I am, why do scientists and teachers (including yourself) constantly refer to brain size instead of brain structure? I hope the question is not stupid. If it is, perhaps my brain is too small.

Well James, you’re right- brain structure is important, but so it brain size. But it’s not just brain size as a single measurement- what seems to be most important is the ratio of brain size to body size. That is, the higher the ratio, the more brain per body weight, and the more intelligent the animal. This is called the Encephilization Quotient, or EQ. Primates have some of the highest EQs of all mammals, with humans obviously at the top of that list. Dolphins also have a very high EQ, which shouldn’t be any big surprise, since they’re widely known to be relatively intelligent also. Interestingly, octopi have the highest EQ of any invertebrate animal, which means they may be spineless, but they’re pretty smart. But EQ isn’t a perfect measurement- because of their small size, shrews have the highest EQ, and they don’t seem to be particularly intelligent. So absolute brain size is also important. Curiously, Homo neandethalensis, or Neanderthal Man, had a larger brain than modern humans, but there is no indication that they were particularly intelligent, or at least more intelligent than the human ancestors that lived at that time. This may have been because they lacked language, since their throat structure wasn’t likely condusive to the development of language. The development of structures within the brain, specifically the neocortex, is what sets humans apart from other organisms. This region of the brain is where the intellectual and reasoning capacity exists, and differences in this region are likely more important among humans for determining intelligence than absolute brain size.

The next question is from DR, who writes:

In your last podcast, #123, you gave examples of homosexuality in other animals. But all the examples seem to show 'homosexual behavior' but overall the animal was bisexual. Are there any examples that we know of where the animal is purely homosexual. For example, I have friends who are homosexual who do not mate with women--they are not attracted to women at all--there is no sometimes. That is homosexuality. In the examples you gave all the animals were bisexual. So are there any animals that are homosexual (besides human animals of course) ?

This is true- the examples that I gave were of various species pursuing homosexual interactions part of the time, while also pursuing heterosexual interactions for the other part. The purpose for doing so was to show that homosexual behavior is not fatal to evolutionary theory, and in fact can provide reproductive fitness to the population. But there are many examples of individuals in populations seeking out exclusively homosexual interactions- I’m sure many of you have heard of the “gay penguins” that refuse the attraction of females, and studies have seen that some male bighorn sheep actually prefer males to females. It’s just as tricky defining this as strictly homosexual in terms of orientation, because we can’t actually ask the animals which they prefer, and even in humans, many heterosexuals engage in some homosexual interactions at some point, and many homosexuals engage in some heterosexual interactions at some point as well. So, remember that I said sex isn’t black or white? This is why.

The next email is from Eddie, who writes:

I debate often with creationists in an internet chat room and the issue of random vs. nonrandom comes up often. I enjoyed your podcast on the subject but had one comment. At the end of the podcast, after making a great case that causality/environment is essentially the determining factor in mutation and which mutations survive, you end by saying evolution is both a random *and* a nonrandom process. This i thought re-opened the door on the very debate you were trying to close. As true randomness is theoretically impossible (it would be an effect with no precedent) in a causal system. No computer model of true randomness has ever been created. And there is nothing at all random about evolution. However the extreme complexity of the systems are so far beyond what we can calculate that it just appears random to us.

You’re right- in a deterministic universe, nothing is truly random, but from our perspective, mutations are generally unpredictable events, or at least the specific mutations are unpredictable- we know pretty well that if you expose DNA to UV radiation, you’ll get thymine dimerization, but we can’t predict which bases will and which will not dimerize. We know that mutation rates can change, and that some regions of a genome are more likely to mutate than others, but it’s still a generally unpredictable process. What’s more causally apparent to us are the environmental factors which affect reproduction fitness and mortality- these are obviously nonrandom. So that’s really what I mean by evolution being both nonrandom and random- I hope that clarifies my position.

This next email is from D.B.

Why is it that humans can hear there own thoughts in our heads with out speaking the words that come out of the mouth?

We can hear our own thoughts because all our senses are processed in our brain. So, we don’t technically need our ears to “listen” to something, just as we don’t need our eyes to “see” something. What is an interesting question to consider is whether or not other animals have that same ability. No other creature has such an audible language as humans, but do they represent their thoughts symbolically in their minds as they’re thinking them? It’s something fun to ponder.

Jeff asks:

I was listening to a creationist poodcast the other day when one of the speakers said that Stephen Hawking is a deist.

Supposedly Stephen Hawking said that the universe is so extremely complex, and the probability of the universe and life coming into existence is so small that there must have been an intelligent creator who created the universe.

I would like to know how you would respond to Stephen Hawking's statement from an atheistic point of view.

That quote sounds bogus to me, especially since Hawking just gave an interview in China recently where he said, “There is no evidence for intelligent design. The laws of physics and chemistry, and Darwinian evolution, are sufficient to account for everything in the universe.” But, if you want me to respond to that statement in general, regardless of who actually said it, I would say that it sounds like a combination of an argument from incredulity, and also a misunderstanding of statistics. For example, it is incredibly improbable that I will win the lottery today. But it is incredibly probable that somebody will win the lottery today. Thus, it may have been improbable for life to arise in one specific place, but very probable that it did arise somewhere.

And finally, one last email from John:

Recently, an anti-evolution friend of mine, whose studying computational biology, asserts the following to me contra Darwin:

"the fact that no random polypeptide chain ever folds into a stable native state at all, let alone into a nontoxic one, let alone into a specifically useful one, let alone into a specifically useful one which is preserved through natural selection."

Not being a biochemist or biologist, I couldn't immediately respond. Is this true to your knowledge?

This is a similar problem to the statistical improbability I mentioned in the previous email. It’s true that any given random polypeptide chain won’t fold into a stable conformation, but would likely just flop around with one or two interactions between different residues in the chain. Most proteins are combinations of two different types of conformation structures- a helix, like a DNA spiral, or a back-and-forth folded sheet. What this problem ignores is the fact of selection- if you have a large number of different proteins, most of them will be useless, but one will be useful. It’s just like with the lottery example- it’s improbable that any one person will win, but it’s certain that somebody will win. Just like this, although any random protein won’t fold into a useful structure, the genome doesn’t encode for random proteins, and neither does evolution conserve random proteins. Small random changes are made to individual proteins, and those changes are selected for their relative effect on reproductive fitness, after which the changes are increased or decreased in a population. That’s evolution in a nutshell. You might say, evolution 101. That’s all for this week, take care.

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