He has dyslexia, which makes it difficult for him to read and write.
He flunked out of university repeatedly.
But his dogged determination has seen him awarded two honorary doctorates.
Dr Jack Horner, 67, a US palaeontologist, has gone on to discover many dinosaurs, name 12 species and even inspired the main character in the Jurassic Park novel and movies.
The "dinosaur hunter" has become one of the most famous in the world, and is in Singapore to promote a travelling dinosaur exhibition which he curated.
In an interview with The New Paper on Wednesday, he said: "It's pretty incredible.
All I really wanted to do was to make even the smallest contribution to palaeontology."
Indeed, he has made several discoveries in over 35 years of working with dinosaurs.
In the 1970s, he discovered the first dinosaur eggs in North America, and was the first to prove that dinosaurs cared for their young.
The Museum of the Rockies in the US, where he is curator of palaeontology, also has the world's largest tyrannosaurus rex collection because of his fieldwork.
Two species of dinosaurs are even named after him - Achelosaurus Horneri and Anasazisaurus Horneri.
In the late 80s, novelist Michael Crichton modelled a fictional palaeontologist after Dr Horner.