Pattern of Genetic Control of Structure in the Evolution of Behavior

PATTERN OF GENETIC CONTROL OF STRUCTURE IN THE EVOLUTION OF BEHAVIOR E. LLOYD DU BRUL* An Idea ofEntity Structure is the observable organization that is explicit in the course ofa flow ofenergy. And this goes as well for bones as brains. A living structure is the composition we see at the moment, but as a class ofthings, it has had a past and it will have a future. It has arrived at its present state by continuous, usable renovations of earlier models, each having behaved satisfactorily for survival in its time. This clearly exposes a makeshiftness to biological things so that the whole biological process is opportunistic . Phylogeny is simply the history ofopportunism. This opening gambit says that behavior is inseparable from structure. It forces us to face both sides of an entity at once. Now cybernetics has been proposed as the true science ofbehavior [i]. It treats ofinformation, communication, and control in living and inanimate machines. It is a theory ofmachines, but it looks at ways ofbehaving rather than at kinds of construction. Its lead question then is: What do machines do? But when an anatomist looks at living machines to understand their behavior, his most solid source ofinformation is the structural moiety ofthe entity. Then his lead question is: How do they do it? And so it has become too quaint merely to say that function determines structure—or the reverse— or any such thing. But now it does seem that, by the use ofthe broadest conceptual tools of both structure and behavior, the anatomist can hold the hope ofmaking whole things whole again. And so, to begin with behavior we must talk about structure. Common structural specifications can be found for such seemingly diverse sorts of machines as live or man-made ones. It is well known that when an engi- * Professor ofAnatomy, Colleges ofMedicineand Dentistry, University ofIllinois, Chicago. 524 E. Lloyd Du Bruì · Genetics in Evolution ofBehavior Perspectives in Biology and Medicine · Summer 1967 neer builds a thing to play games, he must somehow build the rules of the game into the machine. The latest sophistication in programing these devices is to try to instai an ability to change its own structure to make it possible for the machine to change its own behavior [2]. But in this case, ofcourse, certain ideological1 rules of change have to be built into the apparatus. Now when nature builds a device to survive, it must build the rules of the game of life into its machine. And this, as we have long understood , has always included the capacity for random change in structure with the concomitant change in behavior on which selection can act for survival. But in both cases the game is played by communicating throughout the system, controlled inputs (information) from the environment, and then controlling outputs (behavior) to the environment according to the established rules of the game. Most current writing about behavior seems to blur its most critical feature. I want to stress a special circularity ofthe systems in which behavior is enmeshed. An engineer's communication system must have five basic parts [3,4]: (1) a source—something that supplies information; (2) a transmitter— something that encodes information; (3) a channel—something that conducts the code; (4) a receiver—something that decodes information; (5) a destination—something on which information acts. Now we can see these specifications met rigorously by the animal-environment situation: (1) environment as source, (2) sense organ as transmitter, (3) neural path as channel, (4) effector organ as receiver, (5) environment as destination. Obviously, the animal is caught in a closed circuit with its environment . It, and its environment at any given moment, is an entity closed to information! Two Crucial Features ofthe Structure ofBehavior The structure of this circuit can be diagramed quite simply. An input from the environment impinges on the living machine at a precise receptor structure. It is directed throughout the organism, finally to emerge via a precise effector structure as an output to the environment. But then the output is an impingement on the environment. It must therefore modify subsequent inputs to the organism, and the circuitry behaves as a positive feedback. In the words...