Leigh Van Valen

Who was Leigh Van Valen?

Leigh Van Valen was an American evolutionary biologist. He was professor emeritus in the Department of Ecology and Evolution at the University of Chicago.

Amongst other work, Van Valen's proposed "Law of Extinction" drew upon the apparent constant probability of extinction in families of related organisms, based on data compiled from existing literature on the duration of tens of thousands of genera throughout the fossil record. Van Valen proposed the Red Queen Hypothesis, as an explanatory tangent to the Law of Extinction. The Red Queen Hypothesis captures the idea that there is a constant 'arms race' between co-evolving species. Its name is a reference to the Red Queen's race in Lewis Carroll's Alice Through the Looking Glass, in which the chess board moves such that Alice must continue running just to stay in the same place.

Van Valen also defined the Ecological Species Concept in 1976, in contrast to Ernst Mayr's Biological Species Concept. In 1991, he proposed that HeLa cells be defined as a new species, which was named Helacyton gartleri.

Van Valen originated the concept of fuzzy sets, prior to the formalization of this concept by L.A. Zadeh.