From Manu, one son became a kṣatriya, another a brāhmaṇa, and another a vaiśya. This confirms the statement by Nārada Muni, yasya yal lakṣaṇaṁ proktaṁ puṁso varṇābhivyañjakam ( Bhāg. 7.11.35 ). One should always remember that brāhmaṇas, kṣatriyas and vaiśyas should never be regarded as members of a caste by birth. A brāhmaṇa may be changed into a kṣatriya, and a kṣatriya into a brāhmaṇa. Similarly, a brāhmaṇa or kṣatriya may be changed into a vaiśya, and a vaiśya into a brāhmaṇa or kṣatriya. This is confirmed in Bhagavad-gītā ( cātur-varṇyaṁ mayā sṛṣṭaṁ guṇa-karma-vibhāgaśaḥ ). So one is a brāhmaṇa, kṣatriya or vaiśya never by birth, but by quality. There is a great need of brāhmaṇas. Therefore, in the Kṛṣṇa consciousness movement, we are trying to train some brāhmaṇas to guide human society. Because at present there is a scarcity of brāhmaṇas, the brain of human society is lost. Because practically everyone is a śūdra, no one at the present moment can guide the members of society to the proper path by which to achieve perfection in life.