A Francis Bacon retrospective that started at the New York Metropolitan Museum yesterday is not for the faint-hearted.

The self-taught British painter (1909-1992), who denied the existence of God, portrays the brutality of humanity in subjects from Popes to a paralytic child walking on all fours. His images illustrate that without God, humans are subject to the same urges of violence, lust and fear as any other animal.

"His wider appeal is a morbid fascination with the expression of violence in human nature," said Gary Tinterow, principal curator of Francis Bacon: A Centenary Retrospective, which is the first major New York exhibition in 20 years devoted to the artist which includes works from throughout his career.

Mr Bacon, an existentialist, saw man as an "accident of evolution", said Mr Tinterow, adding that contemporary artists consistently vote Bacon as one of the great influences of the current era.

Though he drifted aimlessly early in his career, Bacon found his voice as World War II ended and rose to prominence over the next 45 years.

With a predilection for shocking imagery, Bacon's art was dominated by emotionally charged depictions of the human body.

He painted heads with snarling mouths, images of men as pathetic and alone, and a human figure portrayed as bestial, conjuring up the demons he may have lived with.

Suffering from an abusive father, he later relived that pattern with some of his homosexual lovers.

"His early sexual experiences came by older men who were cruel to him," Mr Tinterow said. "His familiarity with cruelty is strongly expressed."

The exhibit also includes archival materials found in Mr Bacon's studio - only available after the death of a man who hated to paint with anyone present, including the subject.