Describe one new mechanism of evolution that scientists learned after darwin's book was published.

Genetic drift/Sewall Wright effect.

Explanation:

Genetic drift causes the change in gene frequency by chance in a small population. In a small population, the individual alleles of a gene are represented by a few individuals in a population. These alleles will be lost if these individuals fail to reproduce. Allele frequencies appear to change randomly as if the frequencies were drifting, thus, a random loss of alleles in small population is genetic drift. A series of small populations that are isolated from one another may come to differ strongly as a result of genetic drift.

The Darwin's theory brought into light the founder effects in which a small population from the major set of population started a new colony which brought in evolutionary changes in the species.