Horner was born and raised near
Shelby, Montana. He was 8 years old when he found his first
dinosaur bone. He attended the
University of Montana for seven years, majoring in
geology and
zoology. Horner did not complete his bachelor's degree due to severe
dyslexia. However, he did complete a senior thesis on the fauna of the
Bear Gulch Limestone, one of the most famous Mississippian
lagerstätten (exceptionally preserved fossil sites) in the world, located in Montana. The
University of Montana awarded him an Honorary Doctorate of Science in 1986. Also in 1986, he was awarded the prestigious
MacArthur Fellowship. In 1993, he received the Golden Plate Award of the
American Academy of Achievement. '' emerging from its egg In Montana during the mid-1970s, Horner and his research partner
Bob Makela discovered a colonial nesting site of a new dinosaur
genus which they named
Maiasaura, or "Good Mother Lizard". The dinosaur bones, originating from a juvenile, were first discovered by Marion Brandvold. Horner then studied the bones, and at first, there was a refusal to return the bones to Brandvold. It contained the first non-avian
dinosaur eggs in the Western Hemisphere, the first dinosaur embryos, and settled questions of whether some dinosaurs were social, built nests and cared for their young. The discovery established Horner's career. He has named several other species of dinosaur (including
Orodromeus makelai, in memory of his late friend
Bob Makela, who had died in a car accident in 1987) and has had three named after himself:
Achelousaurus horneri,
Anasazisaurus horneri, and
Daspletosaurus horneri. Within the paleontological community, Horner is best known for his work on dinosaur growth research. He has published numerous articles in collaboration with Berkeley paleontologist
Kevin Padian, and French dinosaur histologist
Armand de Ricqlès, on the growth of dinosaurs using growth series. This usually involves leg bones in graduated sizes from different individuals ranging in age from embryos to adults. Horner also revitalized the contested theory that
Tyrannosaurus rex was an obligate
scavenger, rather than a predatory killer. While this theory has been widely discussed by the popular press, it has never been a major research focus for Horner. He claimed that he never published the scavenger hypothesis in the peer-reviewed scientific literature, stating that it was mainly a tool for him to teach a popular audience, particularly children, of the dangers of making assumptions in science (such as assuming
T. rex was a hunter) without using evidence. In 2000, teams led by Horner discovered five specimens of
T. rex and three more the following summer, including one larger than the specimen nicknamed
"Sue". The new fossil was 10% larger than other specimens and estimated to weigh 10–13 tons in life. The
Museum of the Rockies, as the result of continuing fieldwork, now exhibits the largest
Tyrannosaurus rex collection in the world. Currently, Horner is working on the developmental biology of dinosaurs. Horner has published over 100 professional papers, eight books including
Dinosaurs Under the Big Sky; a children's book,
Maia: A Dinosaur Grows Up; a non-fiction book on dinosaurs from Montana,
Dinosaur Lives; and numerous articles. He was also a part of a 2005 discovery of soft tissue in a
T. rex fossil. Horner was the Curator of Paleontology at the
Museum of the Rockies, the Regent's Professor of Paleontology, adjunct curator at the
National Museum of Natural History, and taught at the
Montana State University in Bozeman, Montana. Over the years he has advised people who have gone on to be leading experts in paleontology, such as
Mary Higby Schweitzer,
Greg Erickson,
Kristi Curry-Rogers, and David J. Varricchio. Horner was awarded an honorary doctorate by
Pennsylvania State University in 2006 in recognition of his work. In 2003, Horner discovered a fossilized tyrannosaur leg bone from which paleontologist Mary Higby Schweitzer was able to retrieve proteins in 2007. In 2009, the
National Geographic Society released a documentary entitled "Dinosaurs Decoded", which reviews Horner's research into juvenile dinosaurs. He suggests that juvenile dinosaurs looked sufficiently different from adults, and that they have sometimes been mistaken for separate species. The program examines specific changes that occurred as dinosaurs aged and speculates on why the changes were necessary. Horner's research on the topic has gone as far as eliminating several "sub-species" of
Triceratops,
Pachycephalosaurus, and
Tyrannosaurus. Horner also believes that if his research were to continue as much as a third of known dinosaurs would be classified under an existing species. On November 2, 2013, Horner was awarded the Romer–Simpson Prize, the highest honor a paleontologist can receive from the
Society of Vertebrate Paleontology. On his retirement from Montana State University on July 1, 2016, the MacMillan Foundation honored Horner for his work with a $3 million endowment for the John R. Horner Curator of Paleontology Chair for the Museum of the Rockies/ Montana State University - funding the work of his Paleontology successors in perpetuity. In popular culture, Horner is the subject of the children's book,
Jack Horner, Dinosaur Hunter! written by
Sophia Gholz, illustrated by Dave Shephard, and published by Sleeping Bear Press. The book, which has been translated into French, chronicles the life of Horner, from a child in Montana to an adult on the set of
Jurassic Park, and discusses Horner's scientific contributions as well as navigating life with a reading disability. In 2025, Jack Horner co-wrote a novel with author Julian Michael Carver, an author known for dinosaur-related projects, called
Dinosaur Valley. In
Las Vegas on January 15, 2012, 65-year-old Horner married Vanessa Weaver, a 19-year-old Montana State University undergraduate paleontology student and volunteer in his lab. The couple had divorced by August 2016, but remained good friends. ==Build a Dinosaur Project==