Population & all Creations from the Body of Brahma!
From Srimad Bhagavatam (Canto-3, Ch-12)
Once upon a time, when Brahmā was thinking of how to create the worlds as in the past millennium, the four Vedas, which contain all varieties of knowledge, became manifested from his four mouths.
The four kinds of paraphernalia for conducting the fire sacrifice became manifest: the performer [the chanter], the offerer, the fire, and the action performed in terms of the supplementary Vedas.
Also the four principles of religiosity [truth, austerity, mercy and cleanliness] and the duties in the four social orders all became manifest.
Beginning from the front face of Brahmā, gradually the four Vedas — Ṛk, Yajur, Sāma and Atharva — became manifest.
(BRAHMA MANIFESTS FROM GARBHODAKASAYI VISHNU! READ HERE!)
Thereafter, Vedic hymns which had not been pronounced before, priestly rituals, the subject matters of the recitation, and transcendental activities were all established, one after another.
He also created the medical science, military art, musical art and architectural science, all from the Vedas. They all emanated one after another, beginning from the front face.
Then he created the fifth Veda — the Purāṇas and the histories — from all his mouths, since he could see all the past, present and future.
All the different varieties of fire sacrifices [ṣoḍaśī, uktha, purīṣi, agniṣṭoma, āptoryāma, atirātra, vājapeya and gosava] became manifested from the eastern mouth of Brahmā.
Education, charity, penance and truth are said to be the four legs of religion, and to learn this there are four orders of life with different classifications of castes according to vocation. Brahmā created all these in systematic order.
Then the thread ceremony for the twice-born was inaugurated, as were the rules to be followed for at least one year after acceptance of the Vedas, rules for observing complete abstinence from sex life, vocations in terms of Vedic injunctions, various professional duties in household life, and the method of maintaining a livelihood without anyone’s cooperation by picking up rejected grains.
The four divisions of retired life are the vaikhānasas, vālakhilyas, audumbaras and phenapas. The four divisions of the renounced order of life are the kuṭīcakas, bahvodas, haṁsas and niṣkriyas. All these were manifested from Brahmā.
The science of logical argument, the Vedic goals of life, and also law and order, moral codes and the celebrated hymns bhūḥ, bhuvaḥ and svaḥ all became manifested from the mouths of Brahmā, and the praṇava oṁkāra was manifested from his heart.
Thereafter the art of literary expression, uṣṇik, was generated from the hairs on the body of the almighty Prajāpati.
The principal Vedic hymn, gāyatrī, was generated from the skin, triṣṭup from the flesh, anuṣṭup from the veins, and jagatī from the bones of the lord of the living entities.
The art of writing verse, paṅkti, became manifested from the bone marrow, and that of bṛhatī, another type of verse, was generated from the life-breath of the lord of the living entities.
(Origin of Demigods from the Universal form of Supreme Lord! READ HERE!)
Brahmā’s soul was manifested as the touch alphabets, his body as the vowels, his senses as the sibilant alphabets, his strength as the intermediate alphabets and his sensual activities as the seven notes of music.
Brahmā is the personal representation of the Supreme Personality of Godhead as the source of transcendental sound and is therefore above the conception of manifested and unmanifested. Brahmā is the complete form of the Absolute Truth and is invested with multifarious energies.
Thereafter Brahmā accepted another body, in which sex life was not forbidden, and thus he engaged himself in the matter of further creation.
O son of the Kurus, when Brahmā saw that in spite of the presence of sages of great potency there was no sufficient increase in population, he seriously began to consider how the population could be increased.
Brahmā thought to himself: Alas, it is wonderful that in spite of my being scattered all over, there is still insufficient population throughout the universe. There is no other cause for this misfortune but destiny.
While he was thus absorbed in contemplation and was observing the supernatural power, two other forms were generated from his body. They are still celebrated as the body of Brahmā.
The two newly separated bodies united together in a sexual relationship.
Out of them, the one who had the male form became known as the Manu named Svāyambhuva, and the woman became known as Śatarūpā, the queen of the great soul Manu.
Thereafter, by sex indulgence, they gradually increased generations of population one after another.
O son of Bharata, in due course of time he [Manu] begot in Śatarūpā five children — two sons, Priyavrata and Uttānapāda, and three daughters, Ākūti, Devahūti and Prasūti.
The father, Manu, handed over his first daughter, Ākūti, to the sage Ruci, the middle daughter, Devahūti, to the sage Kardama, and the youngest, Prasūti, to Dakṣa. From them, all the world filled with population.
(Different kinds of Nine Creations and Three Annihilations! READ HERE!)