The number 72 can be found in most cultures, especially those whose history or religion were influenced by stellar observations.
The pole star, or North star, of earth changes slightly every year. It is almost unnoticable, except by cultures who have kept long term records of the movements of the stars. This led to the discovery of the precession of the equinox which completes a full "year" and returns to it's starting point in around 25,920 years. One degree or 1/360 of this cycle is 72 years long.
The constellation Virgo contains a yellow dwarf star known as 70 Virginis. Nearby are two of the brighter stars in this region of the sky, Arcturus and Spica; with Spica in Virgo and Arcturus in Bootes/The Herdsman. These three stars constitute what can be called The 72 Virgins, which hints at the possibility that the Moslem idea of being granted 72 virgins in the afterlife (the "heavens") when one is martyred might be a reference to the stars in these two constellations.
Near the dawn of human history (3100-3700BC), the sun would pass into Virgo on the Spring Equinox at around March 22nd and would be at it's highest point three months later on the Summer Solstice of around June 21st. The seasons themselves are broken down into four groups of three. In some allegorical stories, such as biblical ones, the lengths of days, months and years are mixed around to slightly veil what is being spoken of. For instance, three days of death might represent the three months death of the sun starting at the Winter Solstice and leading to resurrection on the Spring Equinox; taking place in December and then in March, respectively. This three month period, usually dealing with the sun and seasons, may be represented as three days, which in turn equals 72 hours. Additionally, the 72 hour period may be the 3 days of the New Moon, and later connected to the 3 days of death and resurrection.