John Holland, a pioneer in the study of complex adaptive systems and the leading figure in what became known as genetic algorithms, passed away Sunday morning, August 9, 2015, in Ann Arbor, Michigan. 

He was a Santa Fe Institute professor and external professor for many years and, at the time of his passing, a member of the Institute's Board of Trustees and Science Board.

Holland, 86, a longtime professor of computer science and engineering and professor of psychology at the University of Michigan (where he founded and led the Center for the Study of Complex Systems), had been interested for six decades in what are now called complex adaptive systems, starting with his early work at IBM in the 1950s on computer simulations of Hebb’s theory of cell assemblies.

He formulated genetic algorithms, classifier systems, and the Echo models as tools for studying the dynamics of such systems. 

In 1975, Holland published the groundbreaking book Adaptation in Natural and Artificial Systems, which has been cited more than 50,000 times and has been published in several languages. Intended to be the foundation for a general theory of adaptation, this book introduced genetic algorithms as a mathematical idealization that Holland used to develop his theory of schemata in adaptive systems. Later, genetic algorithms became widely used as an optimization and search method in computer science. Most optimization textbooks now include a chapter on such evolutionary algorithms, and his insights led to the field of evolutionary computation.

Holland's statistical learning system, known as the Learning Classifier System (LCS), incorporated a reinforcement learning algorithm for non-Markovian environments (the bucket brigade), which anticipated by nearly a decade the development of non-Markovian learning algorithms. His 1989 book Induction, co-written with psychologists Keith Holyoak and Richard Nisbett, summarized this work and applied his ideas about classifier systems to induction in cognitive science.

His subsequent books Hidden Order: How Adaptation Builds Complexity (1995), Emergence: From Chaos to Order (1998), Signals and Boundaries: Building Blocks for Complex Adaptive Systems (2012), and Complexity: A Very Short Introduction (2014), summarized his more recent work, which helped mature and formalize the field of complex adaptive systems.

He was an early champion of interdisciplinary approaches to science and engineering, and many of his lesser-known projects anticipated important trends and advances in modern computer science. Holland trained several generations of graduate students, many of whom have taken inspiration from his interdisciplinary approach to make seminal contributions of their own.

Holland was one of the intellectual founders of SFI and was the founder of SFI’s Adaptive Computation program, started in 1990. His broad view of complex adaptive systems, computation, evolution, and cognition have become foundational concepts in complexity research worldwide.

"John is rather unique in that he took ideas from evolutionary biology in order to transform search and optimization in computer science, and then he took what he discovered in computer science and allowed us to rethink evolutionary dynamics," says SFI President David Krakauer. "This kind of rigorous translation between two communities of thought is a characteristic of very deep minds. And John’s ideas at the interface of the disciplines continues to have a lasting impact on the culture and research of SFI."

In 1994, Holland gave the first SFI Stanislaw Ulam Community Lectures in Santa Fe, an annual series that continues to this day. (Read about Holland's Ulam lectures in the Winter 1994 issue of the SFI Bulletin.)

"For those of us who knew him personally, John's enthusiasm for ideas was contagious," says SFI External Professor Stephanie Forrest, one of his PhD students at Michigan in the 1980s. "He leaves us not only with a grand intellectual legacy, but with memories of the pure joy he brought to his research, cheerful disregard of academic dogma, and a great sense of fun and mischievousness."

Among his many achievements, Holland became a MacArthur fellow in 1992 and was a fellow of the World Economic Forum.

"I have more ideas than I can ever follow up on in a lifetime, so I never worry if someone steals an idea from me." -- John Holland, 1929-2015

Read Holland's obituary in The New York Times (August 20, 2015)

Read his obituary in The Washington Post (August 19, 2015, written by SFI External Professor Scott Page)

Read his obituary in The Scientist (August 21, 2015)

Read the University of Michigan obituary (August 14, 2015)

Read the obituary on the National Center for Science Education website (August 11, 2015)

The Santa Fe Institute invites friends and colleagues of John Holland to share memories of his life and career in the comments below (moderated).