Looking at the so many forms of life that surround us, one cannot but feel wonder and excitement. So many forms of animal life, so many flowers, insects, birds, with the most intricate form of mating and the most incredible ways of survival under the most difficult conditions. Yes, we generally accept that the biodiversity is a product of evolution. But this statement leaves open a big question: is there a purpose in the design of nature? Why over 40 thousand different species of butterflies, and why so many kinds of roses? To which purpose? And lizards, for example, or spiders: why are they there, what for?

One traditional answer, at least in our western culture, has been: God. God, in his imprescriptible mind, has made all with an intelligent design that we humans cannot understand. In the medieval time, and for centuries afterwards, people were satisfied with this answer. The problem came with a man by name Charles Darwin, in the middle of the nineteen century, who introduced the notion of evolution, saying that the living species were not immutable and made once and for all by God, but had been evolving and changing from a common ancestor. All under the driving forces of natural processes and natural parameters. Even the origin of life, he mentioned, could be due to physico-chemical natural forces.

Actually, the controversy between the God design, and the natural laws, was present much before Darwin. In 1802, William Paley, an Anglican priest, had written a famous book, "The Watchmaker", where he was arguing that the things of life were too complex to be made spontaneously by natural processes, and that therefore only God could be responsible for the designs of life. And today, more than two centuries after that book, the same arguments are presented by the creationists, who with the notion of intelligent design also fight against the concepts of evolution.

Scientist nowadays, with very few exceptions, do not hold to creationism and to the notion of intelligent design. Even scientist who are convinced believers, like the late Christian de Duve, accept the idea of an evolution without predetermined goals. No purpose in nature. But how it is then for life itself? Actually, considering the origin of life on Earth, we may go deeper in this argument.

Scientists in the field would agree that the pathway that goes from inanimate to animate matter must follow the natural laws- the laws of physics and chemistry. From this common denominator depart however two quite different points of view, both in the framework of science- forgetting the divine intervention. The one, which we will call deterministic-better would be to say “absolute determinism”, states that the origin of life on Earth was an inescapable outcome of the original initial conditions on Earth. In general, determinism means that we are dealing with a sequence of events, each one determined causally by the preceding one, and causing by necessity the next one. According to this view, then, the laws of nature are channelled into a narrow road that has to conduct to a well-defined goal: life itself.

What is the alternative point of view? It is one that goes under the keyword of contingency. This is something that in the old nomenclature would be called “chance”- and in fact one of the basic literature milestone is J.Monod’s book “Chance and necessity” (1971).

Contingency is in fact a more sophisticated concept than the vague term chance. It indicates the simultaneous occurrence of various per sé independent factors which determine one event in a given time/space situation. Take the example of a tile that falls from the roof of an old house and strikes to death a pigeon which was peacefully flying beneath. Certainly a “chance event”- but this depends on the speed by which the birth was flying, on the angle by which the tile stroke the pigeon, on the density of the tile, on the age of the roof, from the wind blowing in that particular moment... All these factors are independent from one another, and their juxtaposition has determined that deadly accident. And, importantly: change only one of these parameters (the bird’ flying velocity, the age of the roof, …) and the event would not have happened. Contingency, as Gould states, is characterized by the tyranny of one parameter.

Two different points of view-but notice also that contingency and determinism come always the hand in the hand. Contingency cannot go without the laws of nature: in the example of the pigeon given before, the gravity, the density, the laws of motion, of course are there to determine all movements and the final event. This is so also in the things of biological evolution: if by contingency wings are invented, eventually they have to sustain the flying according to the laws of gravity and have to respect the thermodynamics of blood flow in the animal, etc. The image which is often give-see next figure- is that of a water fall rolling downhill from the top of a mountain: this event is mostly determined by the gravity law, but the actual pathway of the water downhill is determined by the accidents of the ground- bulges and grooves and holes and walls.

However, even if they are together when they operate in real nature, there is a profound difference between the determinism and contingency: that the former states that a given process has to go in a precise way, and contingency instead states that it may go in a quite different way-or that it may not happen. With contingency you can never predict the future, with (absolute) determinism you do.

Going back to the question of the origin of life on Earth, an extreme form of determinism is given by the already cited Christian de Duve, who in his 2002 book states:
… It is self-evident that the universe was pregnant with life and the biosphere with man. Otherwise, we would not be here. Or else, our presence can be explained only by a miracle…

And generally, the idea that life on Earth can be seen as a deterministic pathway of highly probability is to be found frequently in the literature.

I personally believe that this view is flown by a basic conceptual mistake. In fact, to say that the natural laws may have governed the prebiotic scenario, assumes that the origin of life is deterministically controlled. Now, to invoke a guided determinism toward the formation of life would only make sense if the origin of life would demonstrably be a preferential, highly probable natural pathway. But this is precisely what we do not know-or better, we know that it is not so. The chemical processes leading to life are not under thermodynamic control, and life does not correspond to a minimum of energy, to a stable equilibrium. The statement: “the origin of life must have been highly probable otherwise we would not be here” is based on the faith that life is unavoidable.

One cannot invoke natural laws and then force them into one preferential channel. I maintain that this view is equivalent to a creationistic view, although this is not said expressly by those Authors. Elsewhere, the term “crypto-creationism” has been created to describe this scientific movement (Luisi 2006).

The alternative to determinism is contingency, and Stephen Gould, one of the most authoritative defendants of contingency, has a very famous sentence that he wrote about the Cambrian revolution, which caused the formation of most of the multi-cellular organism on Earth after 2 billion years of dominance of unicellular organisms:
“Run the tape again, and the first step from prokariots to eukatiots may have taken 12 billion years instead of 2” implying that a change in one of the variables, (temperature, pH, salinity, pressure, concentrations…) might had prevented the Cambrian revolution then.

Having said that, namely having accepted the relevance of contingency in the creations of nature, let us go back to the questions raised in the introduction of this short article. We asked: why 40 thousand different species of butterfly? Is it compelling to have precisely this number? Could they have been 20 thousand-or ninety thousand? We have to answer positively to this question.

And now let us pass to our lizard. Was it thee a particular purpose for nature to make lizards? Could we imagine a world without lizards? Well, if they would not be here, nobody would have noticed the lack of them.

And it is so is for all things of nature: if, during the vagaries of molecular evolution, conditions -even only one parameter- would have been different in a critical step, different designs would have been created. Thus, many of our things might have not been here. And, conversely, think of the many flowers, fish, birds... who are not with us, but might have been created by a slightly different pathway of the evolution.

But: if we accept the idea that lizard might have not been here, on this Earth... then how is it with mankind? In force of the logics of contingency, we should then accept the idea that evolution might have not created man. Just like the case of the lizard.

...Our planet without the violence brought about by mankind would be in fact a wonderfully peaceful world- no war, no violence, no pollution... the only problem being, that there would be no man to enjoy it...

References
De Duve, C., Life Evolving: Molecules, Mind and Meaning, Oxford Univ. Press, 2002
Gould, S. J., Wonderful Life, Penguin books, 1989
Monod, J., Chance and Necessity, A. Knopf, 1971
Luisi. P.L., The Emergence of Life, Cambridge Univ. Press, 2006; second edition 2016
Paley, W., see it in Natural Theology, collected from the Appearance of Nature, 12.th edit., Lincoln-Rembrandt Publ., 1986