Monday, June 07, 2004


History Through Its Own Eyes

I want to include a lot of history in these essays. It's more a personal interest than a necessity, though. Many things, from human anatomy to the structure of U.S. presidential elections, make sense only if you know where they come from. Science, though, is not always like this. Each of the physical sciences, physics, chemistry, and astronomy, has its own set of theoretical principles. Chemistry and astronomy use ideas from physics, applied to different areas of nature. They are all to some extent the same science, though, so you have subjects like physical chemistry and astrophysics. The basic principles are often called by the name of the originator, but often the principle doesn't depend on the authority of the originator. On the other hand, the social sciences, psychology and sociology, often tend to identify with one or another individual.

Biology is somewhere in between. Darwin tends to dominate evolutionary thinking, but biologists don't cite Darwin as an authority in the same way that anthropologists cite individuals. Much of the thinking in developmental biology (our main concern here) is based on chemistry, so there is less room for individual opinion. Living things are complicated, though, and there are lots of things that biologists would like to know but can't figure out all at once. So there is room for individual opinions. Issues that involve populations of organisms are often murky; the debates over punctuated equilibrium and sexual selection are examples.

In studying the history of science we have to be careful to avoid what some historians call "Whig history". The Whigs were a political party in England (and in the U.S. until 1856). They were supporters of the English constitution, and tended to view history in terms of their own beliefs. In the history of science this view interprets history in reference to an up-to-date science textbook. Greeks who believed in atoms are heroes, those who didn't are stuck-in-the-mud. For example, Janet Browne, in her biography of Charles Darwin, talks about Charles Lyell, whose geological theory influenced Darwin's thnking:
Lyell turned history to his advantage by giving a long and cleverly argued account of the course of geological endeavour from antiquity to the nineteenth century in which everyone who held the same general idea as he did was praised and the the rest dismissed as "unscientific" in blatantly one-sided style. Like the Whig historians whom he greatly admired, he recreated the history of his subject from the position of the author, not just as one in which the past creaked panifully towards the present, but also as a story in which certain inviolate truhts of nature and liberal principles of thought (as seen by Lyell) were progressively revealed to scholars through the ages.
The problem is that nobody in the past was up to our date in all respects. All scientific thinking happens within a world view, a basic belief in what the world is and how it works. The Greeks who rejected atoms (from the Greek atomos, indivisible) believed that matter could be divided indefinitely. The others couldn't accept infinite division; they believed that there are atoms and the void. Anti-atomists couldn't accept the void, a place where there was nothing.

It is tempting to say that the atomists were on to something, and the anti-atomists were misguided. But atoms as we now know them (or think we know!) came from experiments in which chemists found that elements always combined in definite proportions, which implies that there are particles involved. (Of course we also "know" that atoms are actually divisible into elementary particles, which are themselves composed of quarks.) (The "think" and quotes will be explained next time.)

Usually the world view helps science progress, because it tells you what you can look for. Sometimes, though, it holds progress back. We'll see this especially when we get to Galileo. Occasionally somebody will challenge the world view. If the challenge is successful (which is pretty rare) we call the challenger a "visionary", if not he is a "crank".

Most historians feel that western scientific thought started with the Greek philosophers. Usually we think of Plato and Aristotle, although Plato got many of his ideas from Pythagoras and others.

The world view of the Greeks was enough different from our own that it takes a considerable effort to understand Greek thinking. Benjamin Jowett gives some of this in his introduction to his translation of Plato's dialogue Timaeus.Jowett says that one of the reasons for the obscurity of Greek thinking is that it arose "in the infancy of physical science, out of the confusion of theological, mathematical, and physiological notions, out of the desire to conceive the whole of nature without any adequate knowledge of the parts, and from a greater perception of similarities which lie on the surface than of differences which are hidden from view". Much of what will come in these essays will deal with changes in these aspects.

As one example, Greeks saw that animals move by themselves, and rocks don't. Animals are alive, so the Greeks thought that anything that moves by itself, like a planet, is alive. They also thought in terms of "nature", by which they meant "the nature of a thing". Aristotle believed that there are four elemental substances: Earth, air, fire, and water. A stone is earth, and falls because it is its "nature" to go to the earth. The nature of a rock is to be at rest. Smoke is air, so it is in its "nature" to become part of the air.

Aristotle believed that the planets are carried by crystaline spheres. They have to be spheres, because the only motion that can persist is uniform motion in a perfect circle.

Plato, following Pythagoras, held that "everything is number". This can be taken, in our time, to mean that everything follows mathematical principles. This attitude is an important part of our own world view. The physicist Eugene Wigner, for instance spoke of "The Unreasonable Effectiveness of Mathematics in the Natural Sciences". But this can be a handicap in understanding biology. Evelyn Fox Keller, in her book Making Sense of Life, talks about the ways in which the thinking of biologists is different from that of physicists. (More of that in a later essay.)

Physics and biology look at the world from different directions. Mainly, physicists want to explain the world in as few equations as possible, while biologists want to understand living things. Physicists have a powerful tool, but they pay for it in the limitation to simple systems. The motion of two bodies, for instance the earth and the moon, or the sun and a planet, is explainable. Three bodies are explainable only in special circumstances, such as the Lagrange points. Systems of many bodies can sometimes be explained statistically, as in gases.

Biology is different. All biology is local. Biologists have given up looking for top-down rules for how organisms develop; the organism will surprise you. Eventually these essays will take up these topics in detail.

Biology is organized chemistry, so it follows the laws of chemistry. Chemistry follows the laws of quantum mechanics. So biology follows quantum mechanics. The different thing about biology, though, is that there are a great many influences on a growing organism. A planet will always follow its orbit, because it has only its momentum and gravity. An organism has lots more things, which we'll get into later.

In leaning over backwards to understand the past, though, we have to be careful that we don't fall on our behinds. Some philosophers seem to argue that all knowledge is conventional, and that there really isn't any progress. But we feel confident in saying that the earth moves, and that there is no such thing as phlogiston. Again, more later.

Browne, Janet. Charles Darwin: Voyaging, A Biography. Princeton University Press, 1995.

Friday, June 04, 2004


Two Explanations

I want to explain two things about this blog: The title, and the epigraph.

The title, "If Darwin Were Alive Today...", comes from discussions on ARN (see the previous entry). There is much talk on both sides about "Darwinism". But Darwin wrote almost 150 years ago. Some of his ideas are still valid, some aren't. In particular, Darwin didn't know the source of variation. His basic theory was that organisms vary in heritable ways, and that those variations that promote survival will be passed on to the next generation. (It's more subtle than that, but that's for another time.) My main (but not necessarily exclusive) topic in this series of essays will be the ongoing disoveries in individual development, and the ways in which development can vary.

This leads to a distinction between "narrow-sense" Darwinism and "wide-sense" Darwinism. Narrow-sense Darwinism is the explanations in Darwin's writings. This includes the six versions of On the Origin of Species, but also the rest of his works. In the Origin Darwin claimed that the book was "one long argument"; Stephen Jay Gould argued that Darwin continued the argument in the rest of his writing.

Getting now to the title: I suggest that, given the depth and breadth of Darwin's interests, if he were alive today, he would be intensely interested in the developments I'll be talking about. So wide-sense Darwinism includes all the discoveries of modern biology and paleontology, including things that Darwin couldn't have dreamt of.

Of course he might get into the specialization trap; see the previous post. This kind of breadth, I suspect, is for someone who already has tenure.

The second explanandum, the epigraph, is "Nothing in evolution makes sense except in the light of biology". This is a play on an the title of an essay by Theodosius Dobzhansky, one of the founders of evolutionary genetics. His title was Nothing in Biology Makes Sense Except in the Light of Evolution, arguing that biology as we see it is the result of its history, and has features that can be understood only if we understand where the features came from.

My epigraph comes from the conviction (not mine alone) that the variations that provide the raw material for evolution can be understood only in the light of the processes of developmental biology.

Thursday, June 03, 2004



For the last few years I've been a semi-regular contributor to the discussion fora on the Access Research Network, an organization for the study of Intelligent Design. (Click on "discussion forum".) About half of the participants are supporters of ID, the rest are skeptics. One of the difficulties I perceive in talking about ID vs. evolution is that there is a pervasive misunderstanding of what Darwinism is all about. "Darwin Deniers" argue that random mutation followed by natural selection ("RM+NS") is not sufficient to explain the biological world as we know it. (ID doesn't seem to offer much in the way of explanation either, but that's a different subject.) What saddens me is that "Darwin Defenders" seem to accept the RM+NS formulation.

Darwin's theory relied on variation followed by natural selection. He didn't necessarily believe that the variation was random; that was a contribution of the "Modern Synthesis", combining Darwin with the findings of Gregor Mendel.

Cutting this a little short for now (so that I have something left to talk about): Evolution today is very different from what it was only a few decades ago. The revolution is largely the result of the rise of developmental biology, which is a merging of classical embryology, molecular biology, and the enormous amount of genetic information gleaned from the study of fruit flies (Drosophila melanogaster, for the nerds). This is something of a revolution in evolution, but few people seem to be familiar with it. So I am starting this blog, in which I hope to be able to describe the New World as I see it.

My undergraduate degree is in physics, followed by education in business and in software. I am almost entirely self-taught in evolution-related subjects. Evolution is the central organizing principle in astronomy, biology, and geology (to take them in alphabetical order). Part of the problem is that in order to get tenure in any of these subjects one has to go deeper and deeper into one of the many sub-branches of just one area. ("A specialist is someone who learns more and more about less and less, and winds up knowing everything about nothing.") Stephen Jay Gould wished that paleontologists knew more biology; some developmental biologists argue that evolutionary biologists should know some paleontology. I have never had a professional need to go deeply into any of the relevant subjects, so I have the luxury of being shallow in several. I'll try to tie them together for you.

Of course I get my information from other people -- books, journal articles, even other blogs :-) -- so I will probably misunderstand sometimes. Expert criticism is welcome.

So, the adventure begins.