Srimad Bhagavatam 5.14.30
TRANSLATION
The pseudo svāmīs, yogīs and incarnations who do not believe in the Supreme Personality of Godhead are known as pāṣaṇḍīs. They themselves are fallen and cheated because they do not know the real path of spiritual advancement, and whoever goes to them is certainly cheated in his turn. When one is thus cheated, he sometimes takes shelter of the real followers of Vedic principles [brāhmaṇas or those in Kṛṣṇa consciousness], who teach everyone how to worship the Supreme Personality of Godhead according to the Vedic rituals. However, being unable to stick to these principles, these rascals again fall down and take shelter among śūdras who are very expert in making arrangements for sex indulgence. Sex is very prominent among animals like monkeys, and such people who are enlivened by sex may be called descendants of monkeys.
PURPORT
By fulfilling the process of evolution from the aquatics to the animal platform, a living entity eventually reaches the human form. The three modes of material nature are always working in the evolutionary process. Those who come to the human form through the quality of sattva-guṇa were cows in their last animal incarnation. Those who come to the human form through the quality of rajo-guṇa were lions in their last animal incarnation. And those who come to the human form through the quality of tamo-guṇa were monkeys in their last animal incarnation. In this age, those who come through the monkey species are considered by modern anthropologists like Darwin to be descendants of monkeys. We receive information herein that those who are simply interested in sex are actually no better than monkeys. Monkeys are very expert in sexual enjoyment, and sometimes sex glands are taken from monkeys and placed in the human body so that a human being can enjoy sex in old age. In this way modern civilization has advanced. Many monkeys in India were caught and sent to Europe so that their sex glands could serve as replacements for those of old people. Those who actually descend from the monkeys are interested in expanding their aristocratic families through sex. In the Vedas there are also certain ceremonies especially meant for sexual improvement and promotion to higher planetary systems, where the demigods are enjoying sex. The demigods are also very much inclined toward sex because that is the basic principle of material enjoyment.
First of all, the conditioned soul is cheated by so-called svāmīs, yogīs and incarnations when he approaches them to be relieved of material miseries. When the conditioned soul is not satisfied with them. he comes to devotees and pure brāhmaṇas who try to elevate him for final liberation from material bondage. However, the unscrupulous conditioned soul cannot rigidly follow the principles prohibiting illicit sex. intoxication, gambling and meat-eating. Thus he falls down and takes shelter of people who are like monkeys. In the Kṛṣṇa consciousness movement these monkey disciples, being unable to follow the strict regulative principles, sometimes fall down and try to form societies based on sex. This is proof that such people are descendants of monkeys, as confirmed by Darwin. In this verse it is therefore clearly stated: yathā vānara jāteḥ.