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.
For adults, the RDA for iron is 8 mg/day for men ages 19 and older, and women ages 51 and older. For women 19 to 50 years, the RDA is 18 mg/day. For pregnant women, the RDA is 27 mg/day. For breast-feeding women, the RDA is 10 mg/day for ages 14 to 18 years, and 9 mg/day for ages 19 to 50.