Mary Douglas, who died May 16 at 86, elucidated, as perhaps the leading British anthropologist of the second half of the 20th century, the cult of the pangolin, the abominations of Leviticus, and the explosive tendencies behind Al Qaeda.

In 1949, a neat figure still in her 20s with sharp, intelligent eyes, she found herself living with the Lele people of the Kasai region of what was then the Belgian Congo. Through this fieldwork, the backbone of the Oxford approach to anthropology, she discovered that the pangolin (scaly anteater) was regarded by the Lele as taboo, inedible, and dangerous, yet sacred.

A creature of anomalous appearance, with warm blood but a reptilian shell, the pangolin does not run off like game but rolls itself up. For all the danger with which it was regarded, the Lele incorporated it into a secret rite that expressed a transcendent understanding of the tragic facts of death. “Lele say things which uncannily recall passages of the Old Testament interpreted in the Christian tradition,” Douglas wrote. “Like Abraham’s ram in the thicket and like Christ, the pangolin is spoken of as the voluntary victim.” Initiates of the cult, as they carried its corpse around the village, sang, “Now will I enter the house of affliction.”

“The Lele of the Kasai” (1963) became a classic of anthropology, but already Douglas’s approach was attracting far wider interest. One of her maxims was that “as a social animal, man is a ritual animal,” and she demonstrated that Western society had its rituals as much as the Congo.

In her celebrated book “Purity and Danger” (1966) Douglas caught popular interest by providing an explanation for the “abominations” of Leviticus. The creatures declared by the biblical book of Leviticus to be unclean and abominable as food, such as pigs, had for centuries puzzled commentators. Some took the prohibition to be based on hygiene.

Douglas argued that, far from this being the case, the rules expressed the Hebrew characteristics of holiness: wholeness, completeness, separateness. Leviticus characterizes as “clean,” or holy, creatures of land, sea or air: those that walk on the earth with cloven hoofs and chew the cud; fish with fins and scales in the sea; and two-legged, winged birds in the firmament of heaven. But pigs, for example, are anomalous — they have cloven hoofs but do not chew the cud. “A rule of avoiding anomalous things,” Douglas wrote, “affirms and strengthens the definitions to which they do not conform.”

She went on to apply the same sort of distinctions of clean and unclean to modern Western cultures, where, for example, food is looked on as clean on your own plate, dirty on your lapel, and dirty for you when it is on someone else’s plate. She built such observations into a typology for classifying cultures.

For the last 30 years of her life, Douglas developed and refined — in collaboration and sometimes in sharp debate with fellow anthropologists — what has become known as Cultural Theory.

To the end of her life, Douglas remained lively and incisive in conversation. She was pointed in meeting ill-informed, malicious, or pretentious criticism. Her humor could be laconic. Yet her personality was immediately attractive and companionable.

She greatly valued the drawings by her sister that decorated the covers of her books, and she was glad to complete, weeks before her death, the preparation for publication in book form of essays by her father on fly-fishing.

Mary Douglas was born in San Remo, in Italy, when her parents were on the way home on leave from Burma, where her father was a member of the Indian Civil Service. From the age of 5, Mary was left in Devon with her maternal grandparents. Her mother died when she was 12, and Mary was sent away to Catholic boarding school, where she adored the sense of order. She went to college at Oxford, where she studied anthropology with E.E. Evans-Pritchard shortly after World War II.

At Evans-Pritchard’s advice, she went off to do fieldwork among the Lele, submitting her doctorate in 1953. In 1951, the year of her marriage, she had joined University College, London, as a lecturer, and there she spent 20 happy years.

In 1970 she published “Natural Symbols,” which included a chapter titled “The Bog Irish” in which she held that the dropping of the prohibition for Catholics of eating meat on Fridays took away the cohesion of the group.

In 1978 a change in her husband’s work allowed her to take up an appointment in America. From 1977 to 1985, in academic posts in New York and Illinois, she wrote a series of books on Western societies, notably “Risk and Culture” (with Aaron Wildavsky, 1982) and “How Institutions Think” (1986).

In her 70s and 80s she returned to a study of the Bible and astonished a new audience with her findings in “In the Wilderness” (1993), “Leviticus as Literature” (1999), and “Jacob’s Tears” (2004). She detected highly structured compositional forms in the books of Numbers and Leviticus, and argued that this brought out the intentions of their redactors.

Anthropologists took some interest, but biblical scholars were astounded by her argument that the pattern of the book of Leviticus followed the ground plan of the Jewish tabernacle. This year she published “Thinking in Circles,” a study of “ring composition,” a circular structure to be found in some books, including, she argued, “Tristram Shandy.”