Without a big enough population to sustain the gene pool, there was a gradual accumulation of mutations.

From the second half of the last century onwards, a gradual accumulation of new or newly considered plants has transformed our gardens, mood and view of the dreaded month.

It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates (coccoliths) shed from micro-organisms called coccolithophores.

The gradual accumulation of minute variations did not fit with the facts of heredity.

The fills of the holes was found to be largely stone free, these deposits are thought to be the result of the gradual accumulation of wind-blown material.