This is the most explicit and concise description and definition of natural selection in On the Origin of Species. Darwin’s view here is now amply documented and understood at the most fundamental level of DNA.

Darwin packed this paragraph with all of the elements of the process of natural selection. The phrasing reflects his incomparable knowledge of natural history and his revolutionary new view of nature:

“...variations useful in some way...” – the words of a lifelong collector who appreciated that individual members of a species exhibited variability.

“...the great and complex battle of life...” – unlike his predecessors who viewed nature as a peaceful, harmoniously designed landscape painting, Darwin had observed that nature was a battlefield in which there was tremendous waste and death.

“...thousands of generations?” - Darwin’s grasp of time was critical, his knowledge of geology made him confident that the planet and life were much older than people had once thought, such that there was plenty of time for the process of natural selection to play out. --Sean B. Carroll, molecular biologist and geneticist; and an investigator of the Howard Hughes Medical Institute at the University of Wisconsin.