I found this quite interesting, the story of Jai and Vijay. It’s just not a story but an insight into the evolution of Human being and of course written quite before Darwin.( With due respect to Mr Darwin, as I am a science student)

Jai and Vijay were gate keeper of Vaikhunt, the Adobe of Lord Vishnu.

Once Sankadik munis, children of lord Bhrahma came to visit lord Vishnuji ,but Jai Vijay didn’t allow them to enter the place as they look like little kids. This made Sankadik munis furious and in rage they cursed them to be born as mortal humans on the Earth.

Jai Vijay immediately understood that have committed a big mistake.

Later Lord Vishnu came and inquired about the incidence. By that time Sankadik munis also calm down and asked Lord Visnu to revert their curse, but Lord Vishnu instead diluted the curse because he could not disregard munis also.

Lord gave two choices , either to take seven births on Earth as a devotee of Vishnu, or to take three births as his enemy.

Jaya and Vijaya cannot bear the thought of staying away from Vishnu for seven lives. As his enemies, the Lord would have to incarnate on Earth to vanquish them.Thus they would meet Lord in each of their births. As a result, they choose to be born three times on earth as an enemies of Lord.

In Satyug they took birth as Hiranyaksha and Hiranykasyapu, for which Vishu took two avatars . Varah avatar to kill Hiranyaksha and Narsimha avatar to kill Hiranyakashyapu.

In Treta Tug, they took birth as Ravan and Kumbhkarn and were killed by Rama

In Dwapar Yug, they took a mortal form as Shishupal and Dantvakra, they were killed by Shree Krishna.

The point for highlight is, with each birth their power got reduced.

In Satyug Vishnu had to take two birth to kill the Rakshasa.

In Treta Yug both the asuras Ravana and Kumbhkarn were killed by Shree Ram.

In Dwapar Yug , they didn’t even take birth as the main enemies of Shree Krishna.