Full context:   Human cultures have developed many views of the planet. The standard astronomical symbols of Earth are a quartered circle, , representing the four corners of the world, and a globus cruciger, . Earth is sometimes personified as a deity. In many cultures, it is a mother goddess that is also the primary fertility deity. Creation myths in many religions involve the creation of Earth by a supernatural deity or deities. The Gaia hypothesis, developed in the mid-20th century, compared Earth's environments and life as a single self-regulating organism leading to broad stabilization of the conditions of habitability.