Swamping argument

It took Darwin a year and a half to discover that the author was Fleeming Jenkin, Regius Professor of Engineering at the University of Edinburgh.

Jenkin humorously said in his article "we are asked to believe", suggesting[citation needed] he opposed the theory because it was too much like a religion.

He then introduced the 'swamping argument' to deny the possibility that an occasional monstrous individual, a saltation, could supply an escape from this state of affairs and give rise to a permanent adaptation.

Jenkin made a mathematical calculation for his argument …the advantage, whatever it may be, is utterly outbalanced by numerical inferiority.

[2] Darwin agreed that a variation originating in a single individual would not spread across a population, and would invariably be lost.

Nevertheless, until reading an able and valuable article in the 'North British Review' (1867), I did not appreciate how rarely single variations, whether slight or strongly-marked could be perpetuated.

[3]Darwin concluded that natural selection must instead act upon the normal small variations in any given characteristic across all the individuals in the population.

This solved for him the problem of swamping in large numbers and would shorten the evolutionary process to fit his own calculated age of the Earth.