Industrial melanism is a term to familiarise. Biston betularia, the “poster moth” of evolution through natural selection, made this word immortal. You may call it a victim of the Industrial Revolution (or the coal pollution of England). However, the transformation of this humble creature provided the most powerful illustration of the theory of evolution and accelerated its inevitable journey towards becoming a theorem.
To give a brief background: Biston betularia is a type of peppered moth that had transformed from its pale (typica) form to black (carbonaria) in the last decades of the nineteenth century, coinciding with the industrial revolution in England. The hypothesis for the observed shift is that the pale varieties became prey to the bird predators as the former had become easily distinguishable on the blackened walls of industrialised cities of England, thanks to the coal revolution (and pollution). Accidental mutant varieties with black shades saved themselves from the lookout of the predators and became the most abundant species in the 20th century and continued until a few decades ago.
We have seen it before but repeating. Polymorphism is where two individuals differ in their DNA sequence, and the less common variant is present in at least one per cent of the people tested. The simplest type of polymorphism is when there is a single-letter change in a genetic sequence. That is called a Single Nucleotide Polymorphism (SNP).
Scientists have recently discovered the locations (the sequence and the genes) of the mutations that caused the change of colour from pale to dark. Further, analysis by statistical inference has found that the transposition happened around 1819, consistent with the actual observation of the change (from the dominance of the pale population to the black).
Noone sees its evolution!
The story of the peppered moth’s evolution is both fascinating and confusing. First, we need to realise that an individual white moth never transforms into a back one in its lifetime; the celebrated illustration (The Road to Homo Sapiens) of Rudolph Zallinger may tell you otherwise. It was a crime, though unknowingly, the artist committed against science that etched this faulty image – of an ape transforming into an upright man – permanently into the human psyche. Evolution is not a conscious conversion of one species to another. For example, the original white-moth-dominated society and the new black-dominated can easily have a hundred generations of separation.
Humans, the moths of glass sponges
We can see a moth’s evolution in front of us because a moth has a short lifetime – a few months at the maximum. In other words, given a few decades, we could see a few hundred life cycles of moths. Human evolution is not visible to humans because we can never see a thousand generations of ourselves unfolding before us. That is why we go after evidence, and science delivers. In doubt, ask a glass sponge who has survived this planet for 10,000 years!
The industrial melanism mutation in British peppered moths: Nature
Polymorphism: NIH
Longest surviving living organisms: wiki
The road to homo sapiens: wiki
