He was the first person who learnt Ayurveda from Indra and educated the mankind. Shakatayam has described him in this sense:
The divine son of Bhahma, Devarshi Angina had two sons: Utathya and Brihaspati. At the end of KrutaYuga or at beginning of TretaYug, Utathya's wife Mamta and Bruhaspati gave birth to Bharadwaj. The details can be found out in Matsya, Agni Bhahma or Hariwarsha Puranas as well as in Shree Madbhagwat Gita.
It has been described in Charaksanitha that in the midst of Tretayug the disease like temperature came into existence. It wa saftre the introduction of new diseases that After the development of disease Rishis send Bharadwaj to study Ayurveda from Indra. His Ashrama was in Prayag. (Even today this place is quite popular in the priests).
Saints had long life due to Tapobala (Power got from Taga) and Rasayana (Divyaushadhi i.e. divine medicine) while Bharadwaj had the longest life in all these, as pointed in Autareya Aoranyaki.
He was good friend of the King Prushat of Panchal Desh and the father of Dronacharya, (Guru of Kaurav, Pandav). When Drupad, the son of Prushat became King after death of Prushat, Bharadwaj also passed away. Draupadi, the daughter of King Drupad, was the wife of Pandavs. In Mahabharata war, Drupad and Dronacharya both died. In this way it is sure that Bharadwaj was alive from KrutaYuga till some time before the end of Dwagar Yuga.
Maharshi Atreya, the Guru of Agnivesha learnt Ayurveda from Bharadwaj. Many of his successors also had knowledge of Ayurveda Charak. So ch 12, 25 states about another Bharadwaj also. Atreya cleared the doubt about it and proved the options wrong.
He was the son of Devarshi Atri, divine son of Bramha. The word Atreya can have different meanings like son of Atri or successor of Atri or Shishya (student) of Atri etc. But as in Charaksanhita at different places it is clearly understood that the relation is father- son only.
Atri Rishi was himself the Acharya (teacher) of Ayurveda as stated in, KashyapSanhita. He was the Guru (teacher) of Agnivesha who created CharakSanhita's original Novel 'Agniveshatantra', and Bhed etc. He was also recognised by the name Punarvasu and Chandrabhag. The other two names mentioned in CharakSanhita are Bhikshu Atreya and Krishnatreya.
As Atreya and Bhikshu Atreya are mentioned in one instance (together), these two are definitely two separate identities. But names Krishnatreya and Atreya are not mentioned together at any place so it may be said that these two are names of one person. In this concern Shree Gurupad Haldar Mahadoy's opinion given in 4th ch of Shree Madbhagwat.
Meaning which can be taken from this:
Soma: - Chandra, Chandrbhag in Punarvasu Atreya
Krishnatreya: - Durvasa
Dattatreya: - Bhikshu Atreya
But from paragraph of CharakSanhita Sootrasthan, it seems that being a krishnayajurved: Punarvasu can be called as Krishnatreya. He was a teacher (Acharya) of three Ayurvedas.
Agnivesh was foremost among the disciples of Atreya and the author of the Agnivesh - tantra. Agnivesha is mentioned in Sarngaravadi, Aswadi, Gargadi and Tikakitavadi Ganas of Panini's Astadhyayi. Gold stucker has fixed 7th cent B.C. as the date of Panini. As Agnivesh is mentioned in more than one ganas it is evident that he existed long back and became a historical figure by the time of Panini.
On the second stratum stands Charaka who was the first man to refine the treatise of Agnivesha thoroughly and enlarge it with his interpretations and annotations. His contributions in this respect were so spectacular that the original treatise in its new form began to be known on the name of Charaka himself instead of the original author.
Charaka enlarged the original Agnivesha-tantra in brief (Sutra) style with his annotations (Bhashya). Thus Charaka was the Bhasyakara of Agnivesa's work as was Patanjali for the Astadhyayi of Panini. That is why no wonder that Charaka has been identified as Patanjali, the author of Yogasutra and Mahabhasya.
Was Charaka an individual or a traditional group?
Some scholars' opinion is that Charaka was one of the branches of black Yajurveda and the persons following this branch formed a sect known as Charaka. Thus perhaps Charaka, the annotator of the Charaka Sanita, was a person belonging to that sect. There was also a branch of Atharvaveda/b known as 'Vaidyakarana', now extinct, which was perhaps more intimately connected with the tradition of vaidyas who served the masses while moving from village to village. This very mobile character (Carana) might have been responsible for the nomenclature 'Charaka'. This is supported by the theme of the Charak Sanhita, which is based on movement of the scene of activities from one place to another.
Bhaav mishra said that Charaka was the incarnation of Shesha (Naga). This on one hand proves the identity of Charaka and Patanjali and on the other hand, gave rise to speculations that Charaka belonged to the sect of Nagas who at one time were very powerful and established their footholds in several parts of the country.
Sylvan Levi, on the basis of the Chineses version of the Buddhist Tripitaka established that Charaka was the royal physician of the Emperor Kaniska who belonged to 1st or 2nd Cent. AD. The evidence however doesn't support the fact because Kaniska was a staunch Buddhist and the scholars attached to him like Aswaghosa, Nagarjuna etc. were all Buddhists while Charaka shows his fifth in vedas, brahmanism and positivism. Moreover, it looks improbable that a freely moving mendicant like Charaka might have accepted the bondage of a royal court. Hence Charaka, the annotator of the Charaka Sanhita, can't be the same person as the royal physician of Kaniska. It is possible that the name 'Charaka' being popular at one time was given to more than one person.
Asvaghosha, the poet laureate attached to Kaniska has not mentioned the name of Charaka though he has said Atreya as the pro founder of the School of Medicine. Had Charaka been in his colleagues he must have mentioned him. Lastly, this information found only in the Chinese version can't be taken as authority for establishing a historical fact.
The probable connection of Charaka with Kanishka leads to some more important but hidden points. Kanishka belonged to the Kushana dynasty, which was an offshoot of Shakas who came to India roaming about from Central Asia. As the Kunhan Raja view 'Charaka' not as a Sanskrit word but a Paali word 'Chareka'. Then the word 'Charaka' began to be used for inferior type of people.
In Navanitaka, Charaka is not mentioned as author of the text though Agnivesha is there and the followers of Charaka instead of having been assimilated in the general mass of vaidyas formed a separate group patronized by the Shaka kings. All these facts indicate that Charaka was either himself a Shaka or very close to them so that he had to struggle hard for putting his foot down. Perhaps during the same process, the work of Charaka (the Charaka Sanhita) was mutilated which was redacted and reconstructed by Drudhabala in part.
Drudhabala, son of Kapilabala and resident of Pancanadapura reconstructed the Charaka Sanhita, which was deficient in its one-third part e.g. 17 chapters in Chikisitaasthana and entire sections of Kalpa and Siddhi. He completed the Sanhita in these respects by taking relevant materials from several treatises (then available).
There is difference of opinion as to which Drudhabala reconstructed 17 chapters of Chikitsitasthana. Bengal and Bombay editions of the text represent two prominent views. Cakrapani says that the eight chapters upto yaksma, arsa, atisara, visarpa, dwivnaniya and madatyaya were of Charaka and the remaining seventeen chapters were completed by Drudhabala.
Kapilabala, Drudhabala's father is quoted in Vagbhata's Ashtanga Sangraha (6th Cent A.D.). Drudhabala is quoted by Jejjata (9th Cent A. D.). Chakrapani has quoted both Kapilabala and Drudhabala in one context. Chakrapani also says Vagbhata as following the views of Kapilabala. This shows that Kapilabala preceded Vagbhata and was renowned at the latter's time. Hence Kapilabala and his son Drudhabala may be placed in 4th Cent. AD, during the Gupta period.
Bhaav Mishra, the son of Latkan Mishra is the writer of this Novel. He was a Brahmin by cast. Keeping similarity to ancient Sanhitas, he introduced new thoughts and Dravyas. It is the last and important Novel of Laghutrai. It is popular in critics. Besides existing knowledge, addition of latest knowledge has made ayurveda more comprehensive and rich.