14 Nov 2009

Eying an Example. Creative Evolution. Bergson. Ch.1 Part 9. Examination of the Various Theories with Regard to a Particular Example

by Corry Shores
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Eying an Example

Henri Bergson

Creative Evolution

Évolution Créatrice

Chapter 1

The Evolution of Life – Mechanism and Teleology

Chapitre Premier

De l’évolution de la vie. – Mécanisme et finalité.

9. Examination of the Various Theories with Regard to a Particular Example

9. Examen des diverses théories transformistes sur un exemple particulier

Previously Bergson further clarified what makes his creative evolution theory different from other evolutionary theories. In creative evolution, there is a common impetus that disperses through alternate lines of development. This explains why there are so many similarities between species.

§61 Fertile Examples

Bergson will now give his most compelling example.

The ‘higher’ plants and animals each independently developed their own sort of sexual fertilization.

vegetables and animals have evolved on independent lines, favoured by unlike circumstances, opposed by unlike obstacles. Here are two great series which have gone on diverging. On either line, thousands and thousands of causes have combined to determine the morphological and functional evolution. Yet these infinitely complicated causes have been consummated, in each series, in the same effect. (63a)

végétaux et animaux ont évolué sur des lignes indépendantes, favorisés par des circonstances dissemblables, contrariés par des obstacles différents. Voilà deux grandes séries qui sont allées en divergeant. Le long de chacune d'elles, des milliers de milliers de causes se sont composées ensemble pour déterminer l'évolution morphologique et fonctionnelle. Et pourtant ces causes infiniment compliquées se sont sommées, de part et d'autre, dans un même effet. (64-65).

[Consider this evolution chart below. We see that plants and animals split very early in evolution. And they both share a common unicellular ancestor. It would seem that fertilization was not evolved until after evolution split-off into plants and animals. The image is from the Bordalier Institute. Click on it for an enlargement.]

So both plants and animals reproduce sexually. And yet they each live under very different circumstances. So we cannot say that their common sex-reproduction is an adaptation to a shared environmental condition.

Bergson will now further illustrate the ways that his theory of creative evolution differs from mechanistic and finalistic ones.

Consider first finalist theories. Many anthropomorphic finalists have “laid much stress on the marvelous structure of the sense-organs, in order to liken the work of nature to that of an intelligent workman” (63d). But some might offer a theory that does not suppose there is some inherent intelligent principle guiding evolution. There are very simple organisms that sense light in a very basic way. And “nature offers us many intermediaries between the pigment-spot of the simplest organisms and the infinitely complex eye of the vertebrates” (77-78). So, we can easily conceive of sight developing by means of a gradual process of natural selection, rather than by means of an intelligent designer’s careful craftsmanship. So this would be a good example of adaptation. Bergson hopes to show that neither the mechanist nor the finalist theories explain sight. This will better support his own theory of creative evolution.

§62 Seeing the Example

Many finalists cite the eye-ball as an example of the intelligent design we find in evolution. It is so extraordinarily complex, and it depends on so many details being just right. There are countless elements that are coordinated for a single function. But the Infusorian has a pigment spot that senses light. So the same function is found in a very simple form. Then we need only imagine all the many small evolutionary steps leading-up to the vertebrate eye-balls of today. Hence we may explain an 'intelligent design' as resulting from no more than mechanistic causes. [As the eye tries to perform its function of seeing, it encounters limitations that evolution overcomes: “Thus the progressive formation of an eye as well contrived as ours would be explained by an almost infinite number of actions and reactions between the function and the organ, without the intervention of other than mechanical causes”(65bc).]

§63 Let’s See Eye-to-Eye

[So complex organs result from evolution. Mechanists and finalists have their own ways to explain them. In the case of an organ like the eye, both mechanists and finalists would look at the relation between the organ and its function. The finalist would say that there is a function, seeing, that evolution was striving toward. The mechanist would say that there is an organ that changes and happens to develop this function as a secondary coincidence.] Bergson explains that we encounter too much difficulty if we compare organs and functions when trying to understand such complexities as eye-balls. Organs and functions are two very different sorts of things. So Bergson suggests we compare two things of the same category. We will now look at the eye-balls of two very different species.

§64 Scallop Eyes

Bergson will compare mollusk and vertebrate eyes. More specifically, we will examine the eyes of the Pecten (scallop). Both invertebrate and pecten eyes have similar parts and structure. Yet, "all are agreed that mollusks and vertebrates separated from their common parent-stem long before the appearance of an eye so complex as that of the Pecten” (66ab).

So where does this “structural analogy” come-from?

§65 Looking both Ways

Bergson will first examine at how two different approaches would explain this evolutionary phenomenon. The first would see the resemblance as resulting from accidental variations. The other would regard it as resulting from the direct influence of external conditions.

§66 Mutating Theories

So let’s look first at the first explanation, that the similarities are coincidences. There are two theoretical approaches which would make this assessement. The first is Darwin’s account. He says that species develop slowly by the gradual accumulation of “insensible variations” (66d). Others think that a species “comes into being all at once by the simultaneous appearance of several new characters, all somewhat different from the previous ones” (66d). Hugo de Vries’ experiments led him to a mutation theory of evolution: “Species pass through alternate periods of stability and transformation. When the period 'mutability' occurs, unexpected forms spring forth in a great number of different directions” (67b). So one theory states that the variations happen very slowly, the other says they occur by sudden mutations. Bergson admits that both might be partly true. But what he wants to argue instead is that such similar structures as organs cannot have come about through accidental variations, regardless of whether they are sudden or gradual (67b).

Images from the English translation:

Images from the original French:

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