The Chicago lectures; George Wald, part 1

National Educational radio in cooperation with the University of Chicago presents a short series of lectures designed to initiate a new discussion on the nature of man his place in the universe and his biological intellectual and social potentialities. This lecture the second in the series is entitled biological determinacy individuality and the problem of free will. Our speaker is George Wald professor of biology at Harvard University. Here now is Professor wild science and our time has changed and new unity. We see the universe of matter now as a hierarchy of states of organization stretching from. The elementary particles trons protons neutrons photons. Through atoms molecules organized the aggregates of molecules

and then living organisms. And if you wish finally Animal and Plant Society and this hierarchy of states of organization appears to us now also to represent a temporal sequence. We live in a historical universe in which over billions of years and vast reaches of space this increasing complexity of organization was achieved. And in the course of this development one sees two great qualitative changes that have occurred and those are the ones that I want to talk about tonight. On the one hand the emergence of more family gene.

What biologists call morphology but it will do for the whole process. That is the emergence of things having definite sizes and shapes. And then I don't know his stage. There is the emergence of something new again and that is individuality at the level of the ultimate particles the those ultimate particles don't have anything that we could properly think of as definite sizes and shapes. Each is the center of a force field. This can be thought of as spherical asymmetrical But

with these smaller particles and particularly with the smallest of them that has any rest mass of the electron. Running is in the realm of physical indeterminacy all run second day. That is one is in the wrong and which Heisenberg's Uncertainty Principle holds sway. This principle that says that if one attempts to make a measurement upon such a particle that the error in one's measurement of its position X is a distance of space times the error in ones determination of momentum is equal to or greater than the universal constant of action H.

Or since momentum itself is mass times velocity. One can write this a little more informatively as the error in the determination of position times the error in the determination of the last city is equal to or greater than that constant over the mass of the particle. And the point is that. What this is saying for any particle of small mass is that the more accurately one succeeds in measuring the position the less accurately one can measure the velocity or vice versa. And as a result one can never specify. These things closely. One can do better very much better with protons and neutrons than one can with electrons because protons

and neutrons happen about two thousand times the mass. And as you see in this formula. The bigger the mass the smaller this product. The errors. But. The main broke an atom is composed of the space wept out by the electrons about its nucleus. These electrons that Gore originally described as traveling in orbits since one recognizes by this principle that one can't in fact describe the path of an electron and one perform the etymological feat of changing the term orbit to orbit tell and fuck one recognizes is we've got to an atom is a nucleus composed of

proton usually protons and neutrons and apparently this rather indeterminate cloud of electrons and one doesn't know the positions of the Lost Cities so as to be able to specify them. But one has to be content with saying the probability of finding the electron at various positions around the nucleus. And this probability is expressed as the square of the wave function describing the. Situation of those electrons. Actually it is only as one comes to molecules that. Things begin to have definite shapes and sizes and that's a great transition because

those molecules are the basis for the entire remainder of our story and indeed a great many other stories. The shapes and sizes of molecules are quite definite. These molecules are made of the atoms the atoms are in constant motion but the motion is a gesturing kind of motion around mean positions. And one can state reasonably exactly those mean positions of the items within molecules so that by now it's a quite familiar datum to be able to say. The distances by which items are separated in molecules and the angles of the bonds that they form one familiar example for instance is the little molecules look at H to O and it was a great thing in science when it first was appreciated

that those hydrogens are not any old place or are not in a line but in fact have an angle between them and that angle is one hundred and five and one half degrees and that's the most extreme importance in understanding the properties of water. Many of them hang upon this rather specific geometry. This kind of information. Comes out of X-ray diffraction analysis of molecules and it is by that kind of procedure that one learns these into a Tommy distances and bond angles and shapes of molecules become all important in leading us into the shapes of living organisms and all that concerns them.

Indeed in biology or in biochemistry shape is everything. The shapes of molecules. The whole story because in a living organism molecules depending upon the shape are fitted together intricately and the atoms that go into making living organisms are a particular few that have. Certain quite clear characteristics in this regard. 99 percent of the living parts of living organisms made of only four elements of the 92 natural elements those are carbon hydrogen oxygen and nitrogen and these are three of the larger atoms the carbon the nitrogen and the oxygen.

All have characteristics that lend themselves particularly to the making of organisms. Carbon because it joins with fir or other atoms almost always one of these I've mentioned. Another carbon or nitrogen oxygen or hydrogen and one of the peculiar and special things about the atoms. Carbon nitrogen and oxygen. Is that their interest Tomic distances in forming molecules are almost identical and their bond angles are almost identical with the strange result that if one makes chains of atoms and making molecules. If one makes chains that are composed of these items those chains have an almost identical geometry.

Whether they are made and highly of carbon or however one slips in occasional nitrogen or oxygen atoms. So right this. Morphology is having definite shapes and sizes. It's a very extraordinary thing about molecules and indeed many if you must know much what I would like to say where that time. About this matter. So for example there is a still stranger and more beautiful and profound molecular anatomy that goes with some of the bigger and more important molecules that go to make living organisms. And I think many most or perhaps all of you know about this. So for example the nucleic acids which form the

stuff of genes are tremendous. Giant molecules and. How are they specific and lovely geometry. They take the form of a spiral. This is the famous Watson and Crick model which we have great assurance now to be the correct one. And this is a spiral a right handed spiral. In fact a double spiral in which two such nuclear chains. Have. Rungs passing between them up and down. This beautifully formed spiral. Well this is among other things the way genes are constructed and these genes have as one of them main jobs. The specification of another type of giant molecule of the proteins which made of great chains.

Involving 20 different amino acids and these again these proteins take quite commonly the form of a spiral. Those spirals wind themselves in the natural condition for a nuclear capacity or a protein molecule is to collapse into this beautiful geometry. And from here one can go directly to biological structure because such molecules as this these big ones nucleic acid molecules protein molecules but also some rather small ones phospholipids like lecithin have a tremendous propensity for forming more complex structures. And many times these structures are readily identifiable with the structures we find in living cells. So what this emergence of definite sizes and shapes

that really happens at the level at which atoms combine to form molecules was a great thing in the history of the universe. Now I want to speak to this second great development the emergence of individuality. There are no two living cells and I would be so bold as to say there never have been two living cells that are identical. Even the simplest of them bacterial cells of any kind you may choose are never identical. And if looking at them through an ordinary microscope does not convince one of that one has only to go at them with an electron microscope to see that that's the case. Why is that true. What kind of things a living organism

to present this extraordinary individuality. Well it does for one thing with their enormous complexity. They are. Associations of great numbers of very different kinds a great variety of different molecules. And that in itself that complexity makes identity a very improbable thing. The second point they are not static associations of this great variety of molecules but are dynamic. They are the seat of a constant inflow and outflow. Of energy and material. If you had the kind of vision that would let you see molecules and you were to go into a jungle you could see molecules wandering about the slightest. And in this.

Wandering the ceaseless wandering of the molecules about the jungle you would recognize that there would be a locus of particular association little increase in density of certain kinds of molecules and that would be a monkey in the jungle. This constant inflow and outflow of material. Not alone would make that monkey unique creature among monkeys but would also assure the one that. It was not identical from moment to moment throughout its entire existence. There is another reason for this extreme individuality and that is that the information the genetic information that determines a living creature a monkey an amoeba.

Anything you like a bacterial cell that genetic information is laid out in such nuclei gusset molecules as I've already mentioned. That is it's laid out on a kind of molecular tape in which further kinds of nucleotide which are the units of nucleic acid structure are in some specific sequence in one continuous chain. It's the reading of that sequence that determines the proteins and indeed the eventual structure and composition of the living organism. The physicist Eugene Vega whom you all know he's a Nobel laureate of the US just a couple of years ago I once wrote a very interesting essay in

which he said. To any physicist it is a miracle nothing less that there could be a molecular arrangement such as a living organism capable of reproducing itself. And he went on to explain the virtual impossibility of this to any physicist. And what a mysterious business therefore it was because that information is as I've said in the form of a molecular tape. So I thing a very very small dimensions held together only by chemical bonds. And what Vigneault was pointing out was that this very complicated message which is the genetic message

necessarily particularly because it's of such small dimensions necessarily must be subject to a continuous disordering that it couldn't possibly however well one started it off maintain its order indefinitely as it was used. The virtual impossibility that. By such means is this the message be carried as an orderly message as an unchanged message and that organisms genuinely succeed in reproducing themselves. Well fortunately for us all. Even for Eugene Vigneault no such miracle occurs. The genetic message is continuously distorted. The disorder in that genetic message is what we know as

mutation. It's happening all the time. No organism really in fine exactly reproduces itself always there is something new that comes out of it if only for this reason. ANDERSSON matter of fact. That is not at all an imperfection in the order of living organisms. On the contrary it's what makes them work at all. Because it is precisely that continuous outpouring of genetic variations. That the struggle for existence works upon in natural selection. The development of living organisms. Their evolution is an entirely different kind of process

from technological design technological design proceeds by setting down specifications and then doing one count to meet them one knows what one wants to achieve before hand and then one sets about it as skillfully as one can. But that's not the way that living organisms are designed the whole operation of organic design is. That kind of thing in reverse. The way organic design works and the process is the one that Darwin taught us a little over 100 years ago as natural selection. The way it works is by this continuous outpouring of inherited variations owing precisely to make no was pointing out a necessary constant disordering of this molecular message.

And that is that outpouring of variations. From which natural selection is constantly weeding out those things that work less well and permitting those things that work a little better to go on. It is not a great all that we deal with and biological design. It's a great editor. The whole process is is one of editing. And. As for this miracle that Vigneault was calling into question and that does not in fact happen all I can say is if it did if it were possible for living organisms in fact to reproduce themselves heredity would seem to be working better than it is but natural selection wouldn't

work at all. Now this disorder. Appears as a random disorder it is certainly unpredictable. It is very very likely because we are back in that world of small dimensions and single units. It is very very likely for these reasons not only unpredictable but. Indeterminate. We have here a paradox to face in a sense because that kind of genetic anarchy that seems to involve the individual must be coupled with a fantastic conservatism in the continuing result. As a biologist would say in biology this

enormous variation that we see in ontogeny the individual and his history must be coupled with a fantastic conservatism in phylogeny the history of the species. We never dreamed how conservative that latter thing was until this was demonstrated just in the last few years. Let me give you an example of what I'm talking about now is that one can measure the sequences of amino acids in proteins. One can't yet measure the sequences of nucleotides and nuclear assets but any day it seems as though that would begin to happen. But now is that we can measure the sequences. Amino acids and proteins and you understand. And the usual protein there are represented 0 or very

nearly all of the 20 different amino acids and these proteins are for the most part very long chains of amino acids in which those 20 different things can come in any proportions and in any sequence. So that literally one could have potentially an almost infinite number of different proteins. Now that we can measure the sequences one can begin to compare proteins of the same sort in a variety of organisms. And this is beginning to demonstrate an astonishing result. For example hemoglobin our blood taken and it turns out. That the hemoglobin of man this protein molecule which is composed of two kinds of protein chain each of 150 amino acids approximately 300 amino acids in some precise sequence.

It turns out that those sequences are identical in man in the chimpanzee and differ by only two amino acids as between man and the gorilla. Well we're separated by at least a few million years from either of those species. And so far as this protein is concerned we have therefore a very slow kind of change to deal with. But there is another closely related protein it's one of the enzymes concerned with cellular respiration called cytochrome c. It is composed. 100 for one chain of 100 for amino acids. That is out of 104 amino acids between man and the rhesus monkey. One of them out of 104 has changed.

But there's something much more remarkable and that is that the nucleic acid that serves as the gene for determining the structure of cytochrome c. We know now that in that nucleus said which is a chain of units called nucleotides of which there are four kinds that it takes three of those nucleotides to specify probably largely through their shape to come back to that form of theme to specify each amino acid so that if we have a chain of 104 amino acids that must be specified by a chain of three hundred twelve nucleotides and others Those three hundred twelve nucleotides only one not three but only one. Because if you change one nucleotide and such a triplet of

three that changes the triplet and that's all that's necessary and indeed all these changes that we've yet learned of involve one nucleotide change.