Somewhere in the ocean there could be a whale that has been alive since 25 years before the USA existed and seven years before Admiral Nelson was born.Scientists have discovered that many mammals may live far longer than expected, meaning the bowhead whale has an average 268-year life expectancy.Although none has been found that dates to 1751, it would explain why a whale found in 2007 had a 200-year-old harpoon lodged in it.