Living creatures originate from Earth and it is to the Earth that they return when they disappear. Living creatures which are divided into four classes have Earth for their primordial essence.
भूमौ जायन्ति पुरुषा भूमौ निष्ठां व्रजन्ति च। चतुर्विधो हि लोकोऽयं योऽयं भूमिगुणात्मकः॥