evolving they can become the Deities. However these deities are not the highest evolved beings. There are beings more evolved than them. The Rishis the seers of truth are more evolved than them. 

The life of human beings and the deities are interdependent. We human beings have a duty to perform towards them. 

Law of re-incarnation 
Lord Krishna says to Arjuna, both you and Me have passed through many many lives, I remember them all but you do not (BG Ch-4; sl-5 ). 

The souls after evolving through 8.4 million sub human species get a human birth. Thereafter, the souls keeps evolving through repeated human births. At an average every soul takes at least a million solar years of healthy living to attain cosmic consciousness or an average of 10,000 human lives. Once a soul has attained the human status it will generally not go down again to the animal level, sometimes however it may have to do so because of bad karma or excessive attachment to some animal. We remain in this cycle longer because of unfulfilled desires. Unfulfilled physical desires and non awareness of our nature keeps us continuing in this cycle. From the human cycle we move on to a superhuman cycle of existence. The type of life one leads in the superhuman scale is beyond human comprehension and cannot be satisfactorily explained. 

Law of God's incarnation (Avatara ) 
Lord Krishna says, 'although I am unborn, imperishable, Lord of all beings I with the help of My power of maya manifest Myself in a human form.(BG Ch-4; sl-6 ) 

Whenever there is a decline of dharma and increase of adharma I manifests Myself. I protect the righteous destroy the evil-doers and reestablish dharma. To do this I come again and again in every age.(BG Ch-4; sl- 7& 8 ) 

The word 'Avatara' means to descend. Bhagavad Gita emphatically asserts that the Lord comes down or descends in human form from time to time. God can and often do use a fully self- realized master and at times even a partially self-realised masters to awaken His children. This He does from time to time according to the need. These Masters are then known in the world as Avataras or incarnations of God or prophet's of God. God comes down either to establish dharma as Lord Krishna says or to awaken His children or to show the children how to enjoy life as a play (Lila) as he had intended it. When the Lord destroys a evil-doer it should be understood that the evil-doers body is destroyed which he is misusing and temporarily removed from the scene of life thereafter he will be given another body to continue and mould his path. 

The qualifications of an Avatara. 

• They are born free. 
• They are born endowed with perfect memory. 
• They are discoverers of new path in the field of Spirituality. 
• They can transmit wisdom by a touch, or even an act of will. 
• They can see the sanskaras or past karmas of their fellow beings.