The Soot Moth

In 1848, the first confirmed specimen of the melanistic, or darkened, form of the soot moth (biston betularia, or peppered moth) was found outside Manchester. Prior to 1800, this form of the soot moth was practically unrecognized in England, but by 1900, they made up 90% of recorded specimens around industrial and urban parts of Britain. Before the Industrial Revolution, the lighter, flecked form of the moth blended in with the tree trunks on which they would rest, and the black forms stood out, making them easier prey for birds. Once heavy coal pollution began darkening forests, the opposite took place, with the dark and unspotted moths becoming nearly invisible against trees and the speckled moths obvious and easy prey. Through natural selection, this led to an increase in the darker form of the moths.

The soot moth is a test case of Darwin’s concept of the “principle of preservation” (that natural selection “acts to preserve and accumulate minor advantageous genetic mutations”) and is one of the “best-established and clearest illustrations of adaptive evolution” (Hensley and James).

In 1869, f. carbonaria was added to the scientific name to establish the relationship of the moth and its form to carbon energy, and in 1896, James Tutt published British Moths, which examines the phenomenon of their evolution.

What is most shocking about the soot moth, both to us and the Victorians, is that it emerged in less than a single human generation, which “underscores the dramatic effect of human action on biotic processes and ‘natural’ mechanisms.” The soot moth showed Victorians that nature was not separate from human activity, and that it was influenced by and subject to human actions in a drastic way. As Hensley and James describe it, the soot moth was “a key episode in man’s still-changing relation to the category of ‘nature’” and it was “one indicator of how aggregated human action can become coded into structures and processes of life itself.”

We see this struggle with separation between nature and humanity in Tess of the d’Urbervilles. The idea that humans and nature could be kept separate, without influencing one another, or even without being one another, was crumbling throughout the Victorian era, and the soot moth is one stark example of this new challenge.

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