Saturday, July 14, 2007

Information in DNA

In a lecture by Richard Lewontin at Berkeley, he mentions the oft-ignored fact that DNA doesn't determine the organism: In fact, it is a combination of DNA and the environment - and these two factors can interact in paradoxical ways - that 'determines' an organism (actually the entire argument is more complex, but if anyone is interested they should see the lecture, I can't explain it better than him). But one specifically interesting matter was the way in which Lewontin put it:

You can't compute an organism from its DNA

That is, given the DNA of an organism, the naive view that a 'sufficiently-powerful computer' could calculate the organism that would develop from that DNA is, just as the name implies, naive and incorrect. To perform such a computation, the computer would also need the environment (and in addition there might be random factors due to quantum physics, but lets ignore that for now).

In other words, DNA contains only part of the information necessary to compute the resulting organism. But things are more complex still. DNA does not directly generate the organism; DNA is used by complex machinery in the cell to generate proteins. Now, that complex machinery itself is generated by the same process, i.e., some interaction between DNA and that machinery itself (or previous copies of that machinery). There is therefore a subtle question here.

The question can be posed using computer science metaphors. Let's say that DNA is 'data', specifically, compressed data (like files on a computer can be compressed: gif files, mp3, etc.). The cellular machinery is a 'program' that uncompresses the 'data'. Now, given a .gif image file, I can ask: Is there enough information in the gif file itself to generate the image (which was used to generate the gif file)? There isn't, in the sense that I need both the file and a program to uncompress the file. We can even pose this question in a quantitative way (sort of): How much of the information in an image is in the gif file generated from it, and how much is in the program used to uncompress it?

An immediate objection to this is that the same uncompressing program is used for all gif images. Yet, an example can perhaps make my point clear. Say that an image file format's uncompressing program contains a little picture of a red gradient. Compressing images then uses that fact, that is, gradients are removed from the images and just 'notes' appear, something metaphorically like "there should be a gradient here, at angle X and size Y". So the actual gradient appears in the program, not the compressed images. In that sense, when I compress a particular image, part of its 'information' is in the compressed image file, and part in the program. (Yet, despite this concrete example, I intend this idea in a more general way.)

So, we might ask,

How much of the information present in an organism's cells is in its DNA, and how much in the machinery that works on its DNA?

Here is one particular consequence of that question. Say that we recover the remains of an extinct animal, like the baby mammoth recently found in Siberia, and let's assume that its DNA is somehow miraculously preserved but the rest of its cells is too degraded to be of use. Do we then have any hope of creating a live mammoth, as in Jurassic Park, from the DNA alone? If there is a significant amount of information in the non-DNA portions of the cell, then we might have a problem. Now, the problem might be solved if the non-DNA portions of a modern elephant's cells are similar enough; metaphorically, that the same 'program' can be used to decompress both mammoth and elephant DNA. In fact this might be expected, if DNA is the primary vehicle of evolution, and the rest of the cellular machinery is more stable - but that is still a question I do not believe biology has yet answered.

Friday, July 6, 2007

Politically Correct Falsehoods About Human Nature

Sociobiology appears prominently in a Psychology Today article (somewhat ironically, in that a non-psychological theory is trumpeted in a publication supposedly concerned with psychology) entitled "Ten Politically Incorrect Truths About Human Nature". Once again we hear how 'for evolutionary reasons, men are attracted to young women for their reproductive capabilities, and since blond hair is an indicator of youth, men are therefore attracted to blond women', and so forth.

Now, there may be quite a lot of truth in such theories. But the problem is that it is hard to discern the truth from the falsehoods. Indeed, much has been said regarding sociobiology being unfalsifiable. In a simpler type of argument, however, let us consider that sociobiology is always used on cases in which it appears to work well, ignoring those in which it doesn't. Here are some examples.

  • If being blond is indeed a factor that makes women more attractive, why is it not more prevalent? In fact, why isn't it ubiquitous? Some might say that it is because men are less attractive with blond hair, so the trait tends to reach a balance. Perhaps; yet I have never seen evidence for that claim, and in fact, sociobiological theory generally claims that appearance is more important for women (whereas power, authority and resources/money are more important for men). Given that, we would expect to see blond hair in more than half of the population - at least given enough time. Thus, the only defense left is that not enough time has passed for the trait to spread. Perhaps. Yet research seems to show people with blond hair appearing in sizable numbers 10,000 years ago in Europe - quite a long time indeed. Not enough?
  • Models are very tall; in fact significantly-above-average height is generally a prerequisite to work in that field. In addition, many women make themselves appear taller using high heels. But why is height attractive in women? Simple sociobiological reasoning seems to imply it should not be a cause of attraction: Tall women tend to have higher levels of testosterone, which implies lower reproductive fitness. Of course there are ways to reason for the opposite result: Height implies health during youth, for example.
  • Body fat is another questionable area. Why are thin women attractive now, whereas in the past fuller women were considered the ideal? There are competing ways to reason about this matter: Being thin is somewhat correlated with youth (people gain weight over time), yet being thin can also imply malnutrition or disease.
Clearly sociobiological theories have something to teach us about human beings. Yet, given a particular behavior, we cannot quantitatively say how much of it is due to sociobiological factors, and how much to other factors (cultural, psychological, etc.). Sociobiology will mature as a science only if and when it becomes a quantitative science, capable of measuring its successes as well as its limitations.

Tuesday, July 3, 2007

Altruism Dialogue

A: "No-one is altruistic. Even when someone does something for someone else, they only do it because they enjoy doing so. Perhaps they enjoy the feeling that accompanies doing good deeds."

B: "How can you tell that people in fact (1) feel good when helping others, and (2) do good deeds for that reason?"

A: "I would say, 'If they didn't, they wouldn't perform the good deeds,' but that is circular logic, of course. So I base myself on personal experience (and let's assume that my personal experience is representative of others, as well, for argument's sake): I feel good when helping others, and if I didn't, I wouldn't help them."

B: "I might say, 'Well, I believe I am doing the right thing when helping others, and if I didn't, I wouldn't help them.' And in fact I do claim that."

A: "But I know that the good feeling is the reason I do altruistic acts."

B: "I can only respond that I know that my belief that my actions are 'right' is the reason for my helping others."

A: "But if you did not feel good when helping others, you would not believe that altruistic acts are 'right'."

B: "Well, if you did not believe that altruistic acts are 'right', then you wouldn't feel good when performing them."

A: "In fact I do not believe that altruistic acts are 'right'."

B: "Well, in fact I do not feel an enjoyable sensation when doing altruistic acts. Not in every case, at least, which is enough to counter your argument."

A: "But surely you feel a good sensation, even if it is far in the back of your mind, when performing an altruistic act?"

B: "Not necessarily; why would I?"

A: "Well, because you know that the act is the right thing to do -"

C: Can we not conclude that "the enjoyable sensation felt when helping others" and "the belief that helping others is the right thing to do" refer to essentially the same 'thing', in some sense?

Monday, July 2, 2007

Skepticism Need Not Imply Boredom

Aliens are back in the news, due to a deathbed confession. Most likely the confession won't convince anybody (the confession comes from an owner of a UFO museum; even if he can't benefit from raising interest in UFOs after his death, presumably friends or relatives of his now own the museum and have much to gain).

But let's ignore the question of the existence of aliens, about which enough (or more than enough) has been said. What is less remarked-upon is the cultural phenomenon of interest in UFOs. This is clearly one of the more striking trends in the second half of the twentieth centuries, including innumerable pop-culture references and scores of fanatics-for-the-cause.

If aliens exist, then that is clearly thought-provoking. But if they don't, then the widespread interest in them is perhaps no less fascinating. In that case, for not-immediately-obvious reasons scant evidence became the basis for a self-sustaining movement. Why do some conspiracy theories die, others linger (such as that concerning the JFK assassination), and others thrive?

Many have said that UFO abduction stories are merely a replacement for, or a contemporary version of, previous myths and beliefs (for example, Carl Sagan's "The Demon-Haunted World"). But in such skeptical interpretations something may be missed, and that is the speed and and wide reach of the current phenomenon of interest in UFOs. Psychological, cultural, sociological, historical and other factors may play a role here, in ways that I do not believe are yet fully understood.

The real danger in these matters is to make them bland, uninteresting, when they are not. "Explaining away" the UFO phenomenon, in the sense of ignoring the fascinating cultural aspects of it, is a shame. Skepticism need not be less interesting than the alternatives.