Did Vasishta's brother sage Agastya have a previous birth?

Question

Most people only know about the fact the famous sage Vasishta, guru of Rama, was one of the mind-born sons of Brahma. What's not as well-known, however, is the fact that Vasishta is no longer the son of Brahma! In fact if you look at the Anukramani for Rig Veda Book 7 in my answer here, you'll find Vasishta listed not as Vasishta son of Brahma, but rather "Vasishta Maitravaruni", i.e. Vasishta son of Mitra and Varuna. Let me explain.

Once the ancient king Nimi, ancestor of Janaka, wanted to conduct a Yagna, so he asked the sage Vasishta to be his priest. Vasishta told Nimi that he had already promised to conduct a Yagna for Indra, so he would conduct Nimi's Yagna afterward. But Nimi didn't want to wait, so he hired someone else to be his priest. When Vasishta found out about this, he was furious, and cursed Nimi to have his soul separated from his body. In response, Nimi uttered the same curse back to Vasishta, so Vasishta's body died and Vasishta's soul was left to wander. Finally, when the gods Mitra (god of friendship) and Varuna (the ocean god) produced two children out of attraction to the Apsara Urvashi, Vasishta was reborn as one of those children, the other being the famous sage Agastya. Here is how the Srimad Bhagavatam describes it:

After beginning sacrifices, Mahārāja Nimi, the son of Ikṣvāku, requested the great sage Vasiṣṭha to take the post of chief priest. At that time, Vasiṣṭha replied, “My dear Mahārāja Nimi, I have already accepted the same post in a sacrifice begun by Lord Indra. I shall return here after finishing the yajña for Indra. Kindly wait for me until then.” Mahārāja Nimi remained silent, and Vasiṣṭha began to perform the sacrifice for Lord Indra. Mahārāja Nimi, being a self-realized soul, considered that this life is flickering. Therefore, instead of waiting long for Vasiṣṭha, he began performing the sacrifice with other priests. After completing the sacrificial performance for King Indra, the spiritual master Vasiṣṭha returned and found that his disciple Mahārāja Nimi had disobeyed his instructions. Thus Vasiṣṭha cursed him, saying, “May the material body of Nimi, who considers himself learned, immediately fall.”

For unnecessarily cursing him when he had committed no offense, Mahārāja Nimi countercursed his spiritual master. “For the sake of getting contributions from the King of heaven,” he said, “you have lost your religious intelligence. Therefore I pronounce this curse: your body also will fall. After saying this, Mahārāja Nimi, who was expert in the science of spiritual knowledge, gave up his body. Vasiṣṭha, the great-grandfather, gave up his body also, but through the semen discharged by Mitra and Varuṇa when they saw Urvaśī, he was born again.

This earlier chapter of the Srimad Bhagavatam provides a bit more detail about the birth of Vasishta and Agastya:

Agastya and Vasiṣṭha Ṛṣis were the common sons of Varuṇa and Mitra, the tenth son of Aditi. Upon seeing Urvaśī, the celestial society girl, both Mitra and Varuṇa discharged semen, which they preserved in an earthen pot. The two sons Agastya and Vasiṣṭha later appeared from that pot, and they are therefore the common sons of Mitra and Varuṇa.

My question is, was this the main birth of the sage Agastya? Given that Vasishta was originally a sage born from Brahma and then later reborn as the son of Mitra and Varuna, is it possible that something similar happened in Agastya's case?

Do any scriptures describe a previous birth of Agastya?

Answer 1

Agastya is an incarnation of both Agni and Vayu. I found the answer in this excerpt from the Matsya Puranas. Once a bunch of Asuras hid themselves in the ocean, so Indra ordered Agni and Vayu to dry up the ocean. But Agni and Vayu refused, because the ocean is home to so many creatures. Indra was furious, and cursed them to take birth as a sage:

There is no question of Dharma or Adharma where Immortals are concerned, and your glory is still more high. O Agni and Vayu! Since you have violated my injunction and have the duties of the Munis not to injure any being, and since you have leaned towards the enemies who are devoid of religion and politics, losing sight of duty and Shastra, therefore You, O fire will now be born along with Maruta, among mortals, in the form of a sage. In that form of the sage Agastya, you will dry up the ocean, after which you will again come back to your Divine form.

And sure enough, Agastya did swallow up the ocean to help the gods defeat the Asuras. He hasn't regained his divine form(s) yet though, because he received a boon that he will remain alive for 250 billion Mahakalpas! (A Mahakalpas is 100 years in the life of Brahma, as I discuss here).

On a side note, it is Agastya's swallowing of the ocean that ultimately led to the descent of the Ganga from Devaloka. Once Vishnu's incarnation Kapila, whom I discuss here, burnt the sons of Sagara to ashes, but their ashes could not be scattered because the ocean had dried up. That is why Sagara's descendant Bhagiratha had to get the Ganga to come down to Earth, to replenish the ocean and scatter the ashes in a worthy body of water.

Answer 2

Shrimad Bhagvatam Chapter 4 Verse 1.36 mentions the following about the birth of Agastya:

He was called Dahragni or Jatharagni in an earlier birth which may relate to the story of Agni being cursed to be born as Agastya as well as the story of his digesting Vatapi (since Jatharagni in Ayurved refers to the digestive fire). The Vishnu Puran Chapter X also mentions him being born to Pulatsya which would again testify to his kinship with Vishrava:

The wife of Angiras, Smriti, bore daughters named Siniválí, Kuhu, Ráká, and Anumati (phases of the moon). Anasúyá, the wife of Atri, was the mother of three sinless sons, Soma (the moon), Durvásas, and the ascetic Dattátreya. Pulastya had, by Príti, a son called in a former birth, or in the Swáyambhuva Manwantara, Dattoli, who is now known as the sage Agastya.

So the birth from Mitra-Varun could be the second birth (just as it was a rebirth of Vasishth) while the first birth of Jatharagni/Dattoli took place in Swayambhu Manvantar.