Charles Darwin Bicentennial – A Tangled Bank

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Last Darwin Post I gave you the famous “Tangled Bank” quote, in which Darwin links the concept of selection to the concept of ecology and thus derives “grandeur in this view of life.”

This is a theme of much of Darwin’s writing in The Origin, and in fact, the Phrase “Tangled Bank” shows up much earlier in the volume.

In the case of every species, many different checks, acting at different periods of life, and during different seasons or years, probably come into play; some one check or some few being generally the most potent, but all concur in determining the average number or even the existence of the species. In some cases it can be shown that widely-different checks act on the same species in different districts. When we look at the plants and bushes clothing an entangled bank, we are tempted to attribute their proportional numbers and kinds to what we call chance. But how false a view is this! Every one has heard that when an American forest is cut down, a very different vegetation springs up; but it has been observed that ancient Indian ruins in the Southern United States, which must formerly have been cleared of trees, now display the same beautiful diversity and proportion of kinds as in the surrounding virgin forest. What a struggle must have gone on during long centuries between the several kinds of trees, each annually scattering its seeds by the thousand; what war between insect and insect—between insects, snails, and other animals with birds and beasts of prey—all striving to increase, all feeding on each other, or on the trees, their seeds and seedlings, or on the other plants which first clothed the ground and thus checked the growth of the trees! Throw up a handful of feathers, and all must fall to the ground according to definite laws; but how simple is the problem where each shall fall compared to that of the action and reaction of the innumerable plants and animals which have determined, in the course of centuries, the proportional numbers and kinds of trees now growing on the old Indian ruins!

(Darwin, C. R. 1869. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray. 5th edition. Pages 86-87)

This is a fantastic example of Darwin’s breadth of interest and integrated mind. He makes explicit reference to the fact that selection is context dependant (“widely-different checks act on the same species in different districts”). He is explicit about the fact that chance is NOT the operative force in organizing nature (a fact that creationists seem to ignore when they speak of the unlikelihood of a tornado passing through a junkyard creating a Boeing 747 and hogwash). He ties in ecological turnover, disturbance, and succession to Native American history and archeology. He even makes a statement about feathers that kinda looks like an incipient “butterfly effect” (but isn’t, quite). Missing from the quote is reference to co-evolution. Here, it is all about “war” (competition). But the next paragraph in the same volume does talk about “dependency of one organic being on another.”

Finally, and this is one of the most important points to remember in thinking about Natural Selection, Darwin notes

The dependency of one organic being on another, as of a parasite on its prey, lies generally between beings remote in the scale of nature. This is likewise sometimes the case with those which may strictly be said to struggle with each other for existence, as in the case of locusts and grass-feeding quadrupeds. But the struggle will almost invariably be most severe between the individuals of the same species, for they frequent the same districts, require the same food, and are exposed to the same dangers.

Page 87

That a member of one’s own species … and to be more specific, a member of one’s own “morph” (same developmental stage, same sex, etc.) is one’s greatest competitor is a key organizing force in socio ecology. This is often the main force that determines the degree to which members of the same species will group together. If the primary food is rare and of high quality, individuals stay apart from each other not only because they seek this food in a widely dispersed pattern, but because foraging together guarantees fierce competition. Only if the food supply is abundant (which also likely means that it is of relatively low quality) can animals be in groups. For many mammal species, there is a constant tension between the benefits of separation (such as reduced competition) and the benefits of staying in a group (such as reduced predation).

In the end there is very little in social or ecological theory that is not found somewhere in Darwin’s writing, up to the genetic social theories of Hamilton first published in 1964.

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