Hindu belief of the diminishing lifespan of man

"The Sutyoog (1st age) is said to have lasted during a period of 1,728,000 years; when virtue and truth prevailed, and man lived 100,000 years. The Tritayoog (2nd age) is a period of 1,296,000 years; three parts of the creation, during that time, obeyed the word of God, and the life of man was 10,000 years. The Dwapuryoog (3rd age) is a period of 864,000 years; during which half of the creation was wicked, and man only lived 1000 years. - The Kulyoog (4th age) is a period of 432,000 years. Men, in this period, became sinful; only one quarter of the human race followed the dictates of God, and the life of man was curtailed to 100 years. According to the Hindoo account, in the present year (1015 of the Hijra), 4684 years of the Kulyoog have elapsed."
          -Mahomed Kasim Ferishta, History of the Rise of Mahomedan Power in India, Introductory Chapter on the Hindoos, p. liv