A post shared on Facebook claims biologist Charles Darwin said, “In the struggle for survival, the fittest win out at the expense of their rivals because they succeed in adapting themselves best to their environment.”

Verdict: False

There is no evidence that the quotation comes from Darwin.

Fact Check:

A 19th century English naturalist, Darwin is best known for his theory of evolution. In his 1859 book “On the Origin of Species,” he presented and explained the process of natural selection, whereby organisms better adapted to their environment tend to survive and reproduce.

However, nowhere in that book, or in any of Darwin’s writings, is the expression to be found. A search of Darwin Online, a database of his collected works, returned no matches. The University of Cambridge’s Darwin Correspondence Project lists a version of this quote on its list of “Six things Darwin never said.” (RELATED: Did Charles Darwin Say, ‘It Is Not The Strongest Or The Most Intelligent Who Will Survive’?)

“I am very familiar with this purported quotation. It is of course not by Darwin,” National University of Singapore science historian Dr. John van Wyhe told The Daily Caller in an email. “It is probably a mid-20th century attempt to summarize Darwin’s theory that has been misattributed to Darwin.”

Indeed, the earliest appearance of the statement was found in a 1962 history textbook called “Civilization Past and Present,” according to the website Quote Investigator, though it may have appeared in earlier editions. The expression is part of a summary of Darwin’s evolutionary theory by the textbook authors, but is not a direct quote from him or his writings.