Some thoughts on ‘randomness’ and ‘chance’ which are largely misunderstood in the debates concerning origins-
Different Senses of Chance
We need to distinguish between two senses of “random”: the one kind that involves a total break in the causal chain, and in which the event is essentially chaotic; the other that requires only unpredictability, such as the decay of unstable atoms, or Brownian motion, but which remains a caused event. These get confused all the time. There is nothing about changes in a genome or a gene pool that is random in the first sense, but much of the second sense. For example, shuffling a deck of cards results in a properly physical process of the rearrangement of each card, yet there is no real way to predict the order of a random shuffle. Cards don’t just materialise in place, but you don’t know what you will end up with (unless you bias the shuffling so it isn’t random).
Gould [1993: 396f] has written about the different senses of “random” and “chance” in science:
“In ordinary English, a random event is one without order, predicatability or pattern. The word connotes disaggregation, falling apart, formless anarchy, and fear. Yet, ironically, the scientific sense of random conveys a precisely opposite set of associations. A phenomenon governed by chance yields maximal simplicity, order and predictability—at least in the long run. ... Thus, if you wish to understand patterns of long historical sequences, pray for randomness.”
Why is this? It has to do with the nature of explanation. An explanation is an answer to a set of questions about something that presents a problem. Historical explanations deal with long and complex processes, with causes that continue back to the beginning of the universe, and are known as etiologies, from the Greek aitos, for ‘cause’. Where does an etiological explanation stop? In science, explanations have to deal with phenomena in their own terms, dealing with the properties of the things being explained. Evolution through natural selection deals with the changes of organisms through time. The causes of mutations are not evolutionary processes; the changes to organisms that result from mutations are. In other words: given that organisms accrue different traits (from whatever causes, and which we now know are mutations) evolution is the result of these in terms of ecological benefits.
Consider an explanation of a falling object’s trajectory. Newton’s laws show that without such things as air friction or rocket exhaust an object falls in a parabola. Yet no object in the existence of the universe has fallen in a mathematically precise parabola. Gravitation from distant objects, winds caused by the weather on a specific day, and friction on irregular surfaces all affect any real trajectory.
A full explanation of the path taken by the cup of coffee my cat knocked onto the floor the other day nees to deal with the history of the manufacture of the cup, the physiology and psychology of the cat, the historical circumstances whereby the cat and cup came into contact, and so forth back to the big bang. Such an explanation is humanly impossible.
These things are “contingent”. Contingency is a technical term used in philosophy and science to label things that are “inessential” to the explanation. There are too many things to be explained, and in any event they do not really affect the efficiency of the explanation. Some things one can take for granted, other things just don’t make a significant difference.
Gould has written that if we could rewind the “tape” of evolution and replay it, the result would not be the same (Gould 1989). Among other things, humans are almost certain not to re-evolve. This is because the number of contingent causes (asteroids hitting the earth, continental drift, cosmic radiation, the likelihood of significant individuals mating and producing progeny, etc) are so high that it is unlikely they would occur again in the same sequence, or even occur at all. If an asteroid hadn’t hit the Yucátan Peninsula 65 million years ago, for example, mammals probably would never have diversified, as they didn’t in the 100 million years before that.
Processes explained by science are affected by their intrinsic properties, the initial conditions and the boundary conditions. The cup fell from 1 meter. That’s an initial condition. There was no real wind, but there was air friction. Those are boundary conditions. The cup had a certain mass and fell in a gravitational field of 1g. Those are the intrinsic properties. These last are not explained by Newtonian physics, but by Einstein’s physics of time and space.
Contingent events are sometimes exceedingly sensitive to the initial conditions. A single slight difference can lead to a radically different outcome. If the cup fell from one meter but into the folds of a rigid tablecloth (a boundary condition), then a millimeter of difference in the way it fell (in its initial conditions) could leave it in pieces on kitchen floor, or in the dog’s sleeping basket and safe, though in need of a wash.
Evolutionary theory explains why objects with certain properties move and change the way they do: how organisms change over time. In evolution, the initial and boundary conditions are contingent. That is the extent, the whole of it, of randomness and chance in the history of life.
Fear of the ordinary sense of chance and random which Gould describes above arises largely from a desire to find meaning in the events of the world around us. Science is not the appropriate place to find this meaning. Neither can meaning be imposed upon scientific explanations. Attempts to impose preconditions on science can have, as they did in the case of Lysenkoism, dire consequences, and at the very least they impede science in its search for adequate understanding of the world around us.