This is a lecture from the book Caitanya-caritāmṛta, Madhya-līlā 6.254 that Srila Prabhupada gave on January 8, 1968 in Los Angeles.
Five thousand years before, Kṛṣṇa spoke this Bhagavad-gītā; still going strong. It's so famous. And Kṛṣṇa claims that sarva-yoniṣu kaunteya [Bg. 14.4]. Most of you must have read Bhagavad-gītā, and in the Fourteenth Chapter you'll find that Kṛṣṇa says, "My dear Arjuna, in all species of life there may be as many varieties of forms." We are all living entities. Here even, even in human society, we have got different types of forms. Nobody will be exactly like the form of another gentleman. There is difference. So this is the beauty of creation. If you go to a tree, there are millions and billions of leaves, and you won't find one leaf exactly like the other. So there are varieties of living entities. Out of the varieties of the living entities, the human kind living entities are very small. From śāstra, from scripture, we understand that there are 8,400,000 species of life, 8,400,000 species of life. Out of that, aquatics, water animals or water-living entities, are 900,000.
The botanist or the physiologist, how many they have seen or how many they have experimented or how many we have seen? But from the śāstra, from the Vedic scriptures, we find that there are 900,000's of species of life in the water, and 2,000,000 species of life in the botanical department. Similarly, there are birds, there are beasts, there are four-legged animals, and at last, the human beings. The human life is considered to be the developed form of all species of life. Darwin's theory also, some idea, gives some idea. I think he might have taken this idea from Vedic literature. But the gradual evolution is recommended, is, I mean to say, mentioned in the Vedic literature that from aquatics to plant life, then worms' life, then birds' life, then animal life... There are thirty-three hundred thousands of animal life. So at last this human form of life. And the human form of life, there are many species, some of them civilized, some of them not civilized. Some of them have no religion. But we can know from the history of human civilization that any civilized nation, it doesn't matter whether he's Christian, whether he's Muhammadan, or a Hindu, or Buddhist—there is some type of religion.