Most male fin and blue whales sing at around 17 to 18 hertz, which is too deep for humans to hear, but the 'lonely' whale communicates at 52 hertz. When more recordings were released in the nineties, Dr Watkins studied the 52 hertz whale more closely.
The average person needs to absorb just a small amount of iron each day to stay healthy (around 1 mg for adult males and 1.5 mg for menstruating females). To achieve this, however, we need to consume several times that amount. This is because our bodies absorb only a fraction of the iron contained in the foods we eat.
Male teenagers ages 14 to 18 need 11 milligrams of iron per day, while female teenagers ages 14 to 18 need 15 milligrams of iron per day. Women ages 19 to 50 need 18 milligrams of iron per day, while men ages 19 and over and women ages 51 and over need only 8 milligrams per day.