Prabhupāda: What does he mean by survive? What is the meaning of his dictionary, "survive"? Nobody survives.
Hayagrīva: Well, by that he means that the strong pass on their hereditary characteristics to their offspring, and that the race..., no individual survives, but that the race improves. But isn't this contradicted by the Vedas? In the present Kali... For instance, Arjuna's physical powers, prowess, was much greater, and that was, what, five thousand years ago. So isn't, instead of improving, instead of the race improving in strength and other qualities, isn't it actually...
Prabhupāda: They are degrading.
Hayagrīva: ...degenerating. What is the cause of man's physical, mental and spiritual deterioration in the succeeding yugas?
Prabhupāda: That is education. Every individual person, he is a soul, and he has got a particular type of body. Especially in the human body he requires education. What is this animal and what is higher than human race, these are Vedic description. So there are 8,400,000 different forms of life, and the body is being evolved. The body is machine, and the individual soul desires and he gets a suitable body made by material nature under the order of God. This is Vedic idea, as it is said in the Bhagavad-gītā, īśvaraḥ sarva-bhūtānāṁ hṛd-deśe arjuna tiṣṭhati (BG 18.61). God is existing within the core of everyone's heart, and the individual soul is desiring something, and upon the order God he is given a machine made by material nature. So this is evolution, and even a man, although he is human form of body, he can again degenerate to animal form of body according to his desire. Tathā dehāntara-prāptiḥ (BG 2.13). He has to change the body, and the body is changed according to his work and desire. In the animal kingdom they have also desires, but they are under the laws of nature changing body, and one is given the chance to become a human being, and then he may desire, and according to his desires he gets the next body. If he likes, he can go higher forms of life, and if he degenerates he goes lower form of life.