Often times we find ourselves encountered with the term ‘manvantara’, especially in Purāṇic literature. What exactly does the term stand for? The term ‘manvantara’ is explained as the lifespan of a manu, and manus are mind-born children of Brahmā. Manus are patriarchs endowed with divine power that enables them to protect the universe and to ensure its smooth progress for an extended period of time. Specifically, they are responsible for the proliferation of mankind. The Sanskrit terms used for man, like ‘mānavaḥ’ or ‘manuṣyaḥ’ for instance, thus derive from the term manu. More importantly, the first manu, Svāyambhuva-manu is the original author of the corpus of laws that must govern man upon earth, the manu-smṛti.
कृते कृते स्मृतेर्विप्र प्रणेता जायते मनुः।
kṛte kṛte smṛtervipra praṇetā jāyate manuḥ|
With the advents of every Kṛya-yuga is born manu, the author of the Smṛti (Manu-Smṛti).
After having given himself to the act of creation, Brahmā found that the created beings did not automatically proliferate. Desirous of producing beings that would further creation, Brahmā created the Brahmarṣis, the seven great sages. To his utter dismay however, Brahmā discovered that the mind-born sages were devoid of any desire or passion, and thus remained aloof from the world around. Finding his purpose defeated, Brahmā finally created the first manu, Svāyambhuva-manu in his own image. He then created Śatarūpā from his feminine energy so that Svāyambhuva-manu could take her for his wife. In order to establish dharma, the Supreme Being incarnated as the four children of Svāyambhuva and Śatarūpā, the daughters Ākūti and Devahūti, and the sons Yajña and Kapila.
A total of fourteen such manus are enlisted in the Purāṇas for each day in Brahmā’s life – Svāyambhuva, Svārociṣa, Uttama, Tāmasa, Raivata, Cākṣuṣa, and Vaivasvata, Sāvarṇī, Dakṣa-Sāvarṇī, Brahma-Sāvarṇī, Dharma-Sāvarṇī, Rudra-Sāvarṇī, Deva-Sāvarṇī and Indra-Sāvarṇī. These manus protect and ensure the smooth progress of the worlds until naimitta-pralaya occurs.
निशावसाने आरब्धो लोककल्पोऽनुवर्तते।
यावद्दिनं भगवतो मनून् भुञ्जंश्चतुर्दश॥
niśāvasāne ārabdho lokakalpo’nuvartate|
yāvaddinaṁ bhagavato manūn bhuñjaṁścaturdaśa||
At the end of (Brahmā’s night) the creation (of the lower worlds) follows, and is sustained through the day when the fourteen manus stand.
The lifespan of each of these manus is termed a manvantara and is described to last for a period of 71 catur-yugas or cycle of four epochs. Loosely calculated, 1 catur-yuga spans 43.2 lakh mortal years. A manvantara is approximated to 30.8 crore mortal years.
A manvantara becomes a significant measurement of time also because each manvantara is marked by its own Indra, its own set of Saptarṣis, its unique celestials, and avatāras.
मन्वन्तरेषु मनवस्तद्वंश्या ऋषयः सुराः।
भवन्ति चैव युगपत्सुरेशाश्चानु ये च तान्॥
manvantareṣu manavastadvaṁśyā ṛṣayaḥ surāḥ|
bhavanti caiva yugapatsureśāścānu ye ca tān||
In each manvantara appear manus, progeny of those manus, sages, celestials and their following (associated with that particular manvantara).
In other words, the post of the king of celestials or Indra, unto whom sacrifices are offered in the sacred fire, changes with every manvantara, as do the celestials for that manvantara. The post of the saptarṣis, who descend upon earth in order to revive the Vedas lost after each catur-yuga, changes with every manvantara, and the offspring of Manu who rule over the earth also changes with every manvantara. Each manvantara is marked by its own set of avatāras was well. For instance, the Viṣṇu-Purāṇa states that the present age is guarded by the Manu, Vaivasvata. Indra during the Vaivasvata manvantara is Purandara. The Saptarṣis are Vaśiṣṭha, Kaśyapa, Atri, Jamadagni, Gautama, Viśvāmitra and Bharadvāja. The illustrious sons of Vaivasvata-Manu who were emperors upon earth are Ikṣvāku, Nābhāga, Dhṛṣṭa, Sanyāti, Nariśyanta, Nābhanidiṣṭa, Karūśa, Pṛṣadhara and Vasumān. Avatāras of the divine too are represented in terms of the manvantara they occurred during. For instance, the Kūrmāvatāra is said to have occurred during the Cākṣuṣa-manvantara. Each manvantara in essence thus becomes a period of time in the endless fabric of time in the Bhāratīya tradition to be associated with celestial occurrences. Purāṇas therefore classify anecdotes with regards to the manvantara they took place during, and are arranged according to the chronology of manvantaras they are associated with.
The Śrīmadbhāgavata states that Lord himself carries out the duties of the various manus.
मन्वन्तरेषु भगवान् बिभ्रत्सत्वं स्वमूर्तिभिः।
manvantareṣu bhagavān bibhratsatvaṁ svamūrtibhiḥ|
In each manvantara, the Supreme lord, his valor apparent, resorts to the attribute of satva and manifests as the various manus in order to protect the universe.
When the prescribed duty of a particular manu is completed, he was replaced by the next manu in line, and the order of the universe became the responsibility of the new manu. In this manner, the lord maintains order in the universe, and provides with the manvantara, particular periods in time, for the unraveling of cosmic events.