Eggs and Easter are now indissolubly linked. But like many of the Christian rituals, the origin lies in other cultures. From China to Egypt, the egg is the symbol of rebirth in spring, and even of the Universe itself. No natural object is more loaded with meaning. The wonder of its shape and the miracle of the life within have an endless fascination.

The largest egg of all, the ostrich's, has drawn intense secular and religious attention. Prized in cabinets of curiosities, the eggs were often given extravagant mounts in silver. In churches they hung in places of honour. The most famous is suspended from the shell niche behind the Virgin in Piero della Francesca's Brera Altarpiece (pictured here), painted in the mid-1460s for Duke Federigo Montefeltro in Urbino.

In the thirteenth century, Bishop Guilelmus Durandus gave two reasons for exhibiting ostrich eggs in church. Like other exotic curiosities, such as unicorn's (really narwhal's) horns, they testified to the wonder of creation. More specifically, they carried an intricate Christian message, derived from the Physiologus or Bestiary, probably compiled in the fourth century from classical, Egyptian and Indian sources. It told of the ostrich's strange incubation habits.

A “careless” creature, says the Physiologus, the “sparrow camel” (Strutho camelus) abandons its eggs in the sand, but returns to hatch them by staring at them. The heat of its sight incubates the chicks, in accordance with the theory that seeing rays emanate from the eye. The Christian interpretation given in the Physiologus and by subsequent writers is that worshippers should keep their eyes on Christ at all times.

These legends may seem to have little to do with what we regard as the science of animals. However, Konrad Gesner, the great Swiss natural historian often seen as the father of zoology, on the basis of the superb illustrations in his Historia Animalium (1551), diligently records stories from the Physiologus and subsequent bestiaries. It seems that we may have incorrectly characterized the origins of modern science.

The learned text supplied for each illustrated beast begins by comparing the animal's names in various languages, a necessary preliminary in the era before standard nomenclature. Then Gesner deals with the animal's appearance and form, its food, generation and life in its habitat, including its enemies. He next outlines its utility for man, before an extensive section on its wider history in various cultures, its symbolic, moral and geographical connotations, and its role in literature.

The appearance of an ostrich egg suspended behind the Virgin in Piero della Francesca's Brera Altarpiece indicates its symbolic importance to the Church. Credit: THE ART ARCHIVE/GALLERIA BRERA MILAN/DAGLI ORTI

The aim was nothing less than a comprehensive review of each animal in its widest context from a humanist perspective. His account emphasizes the ‘history’ in natural history — a name that now applies largely to museums — in the face of the rise of the more ‘scientific’ terms zoology and botany, or, more recently, animal and plant sciences. A significant aspect of the story of the modern sciences of nature consists of combating what came to be seen as the literary, artistic and antiquarian stigmas associated with natural history. Not the least of the avoiding actions was to abandon the deluxe picture-book that had dominated the study of animals and plants from the sixteenth century.

But the legends of the bestiary remain deeply embedded, albeit largely unnoticed, in our own culture. We talk, for instance, of crying crocodile tears, as crocodiles were reputed to weep insincerely after devouring a man. And, of course, if we do not want to face reality, we bury our heads in the sand like an ostrich.