Mbh 6.10.2a

“Sanjaya said,--‘O bull of Bharata’s race, four Yugas set in Bharata’s Varsha, viz., Krita, Treta, Dwapara, and Kali. The Yuga that sets in first is Krita, O Lord; after the expiry of Krita comes Treta; after expiry of Treta comes Dwapara; and after that last of all, sets in Kali. Four thousand years, O best of the Kurus, are reckoned as the measure of life, O best of kings, in the Krita epoch. Three thousand years is the period in Treta, O ruler of men. At present in Dwapara, persons live on Earth for two thousand years. In Kali, however, O bull of Bharata’s race, there is no fixed limit of life’s measure, in so much that men die while in the womb, as also soon after birth. In the Krita age, O king, men are born and beget children, by hundreds and thousands, that are of great strength and great power, endued with the attribute of great wisdom, and possessed of wealth and handsome features. In that age are born and begotten Munis endued with wealth of asceticism, capable of great exertion, possessed of high souls, and virtuous, and truthful in speech. The Kshatriyas also, born in that age are of agreeable features, able-bodied, possessed of great energy, accomplished in the use of the bow, highly skilled in battle and exceedingly brave. In the Treta age, O king, all the Kshatriya kings were emperors ruling from sea to sea. In Treta are begotten brave Kshatriyas not subject to any one, endued with long lives, possessed of heroism, and wielding the bow in battle with great skill. When Dwapara sets in, O king, all the (four) orders born become capable of great exertion, endued with great energy, and desirous of conquering one another. The men born in Kali, O king, are endued with little energy, highly wrathful, covetous, and untruthful. Jealousy, pride, anger, deception, malice and covetousness, O Bharata, are the attributes of creatures in the Kali age. The portion that remains, O king, of this the Dwapara age, is small, O ruler of men.