Refutation of Nilesh Oak’s dating of ancient texts
Sushruta Samhita was NOT written over 7,500 years ago
Refutation of Nilesh Oak’s dating of Sushruta to earlier than 5,561 BCE
The Suśruta Saṃhitā is a well known text of Āyurveda, which describes surgical operations and instruments. The date of its writer, sage Suśruta, is not well agreed among researchers as is the case of many personalities from Indian history. Many dates have been proposed for him ranging from 1000 BCE, 800–600 BCE, 600 BCE, 600–200 BCE, 200 BCE, 1–100 CE, and 500 CE . In a presentation by Nilesh Oak  and another presentation and article based on Oak’s work [3–4], it is claimed that the time of Suśruta was earlier than 5,561 BCE based on the information in Suśruta Saṃhitā. In this article I will point out that Oak’s dating is based on a limited and selective choice of evidence. For example, he selects one part of the passage for astronomical dating while neglecting another part of the same passage that clearly negates his thesis. In addition, Oak is either not aware of or does not disclose other information from Suśruta Saṃhitā that is relevant to his dating methodology and which negates his thesis. Furthermore, the passage used by Oak for astronomical dating is a later insertion in the text. This later insertion has contaminated information of seasons rendering it unusable for dating purposes. Let’s go into the details.
1. Āśvina in Varṣā season and Mārgaśīrṣa in Śarad season
As we know Varṣā season consists of Śrāvaṇa and Bhādrapada and Śarad season consists of Āśvina and Kārttika and so on. It was proposed by Vartak that the grouping of seasons and lunar months changes by one month in every 2,160 years due to precession :
The seasons depend on the Solstices and Equinoxes i.e. on the relation of the Sun and the Earth. Hence due to the precession the Ṛtus shift back on the Lunar months at the rate of one month in (30x72=) 2160 years.
This has been adopted by Oak, who uses a period of 2,000 years for the change of one lunar month . I am going to call this hypothesis as “Vartak-Oak hypothesis”. According to Vartak-Oak hypothesis, seasons consist of different pairs of luni-solar months as time changes. According to Oak [2–4], an example of this changed coupling is found in Suśruta Saṃhitā. Oak quotes Suśruta Saṃhitā 1.6.10 as the basis of his astronomical dating of Suśruta [reference 2 at t = 15:50 to t = 16:50, reference 3 at t = 0:40 to t = 1:12, reference 4]. The text is as follows:
iha tu varṣāśaradhemantavasantagrīshmaprāvṛiṣaḥ ṣaḍṛtavo bhavanti doṣopacayaprakopopaśamanimitta te tu bhādrapadādyena dvimāsikena vyākhyātāḥ tadyathā bhādrapadāśvayujau varṣāḥ kārtikamārgaśīrshau śarat pauṣamāghau hemantaḥ phālgunacaitrau vasantaḥ vaiśākhajyeṣṭhau grīṣmaḥ āṣāḍhaśrāvaṇau prāvṛḍiti
The English translation of this text is as follows :
According to some, the rainy season consists of two months known as Bhādra and Āshvina; Autumn consists of the two months of Kārtika and Mārgashirshya; Hemanta consists of the two months of Pousha and Māgha; spring consists of the two months of Phālguna and Chaitra; summer, of Vaishākha and Jaistha; and Prāvrit, of Āshādha and Shrāvana.
Based on Suśruta Saṃhitā 1.6.10, Figure 1 shows the grouping of luni-solar months and seasons. Please note that the passage does not mention the location of solstices and equinoxes. This is stressed by Tilak in his analysis of this passage :
The second paragraph then begins with the words “But here” and continues to state “But here the six seasons are, — Varshā, Sharad, Hemanta, Vasanta, Grīshma and Prāvṛiṣh,” thus altogether dropping Shishira and dividing the rainy period into two seasons Varshā and Prāvṛiṣh. The paragraph then proceeds to assign the months to the seasons as follows:- Bhādrapada and Āshvina is Varshā, Kārtika and Mārgashīrsha is Sharad, Pauṣha and Māgha is Hemanta, and Phālguna and Chaitra is Vasanta; and so on until all the months are assigned to their respective seasons. The second paragraph, however, makes no mention of the ayanas, the year, or the lustrum.
However, Oak arbitrarily assigns the position of solstices and equinoxes to this passage and proceeds to date this passage. Figure 2 shows the arbitrarily assigned location of solstices and equinoxes to the information given in Suśruta Saṃhitā 1.6.10.
Based on these arbitrary assignments of solstices and equinoxes with no basis to the quoted text, the position of summer solstice is at the beginning of Varṣā season and fall equinox at the intersection of Kārttika and Mārgaśīrṣa. Oak then dates the fall equinox to ~3,000 BCE and summer solstice to ~ 4,000 BCE as described below :
Sushruta Samhita states the following lunar months for the specific seasons of the year. If we understand lunar month of Bhadrapada as the beginning of the Varsha season, i.e. lunar month of Bhadrapada coinciding with the time of summer solstice, it leads us to the time of ~4000 BCE. If we align the timing of Kartika/Margashirsha with the Sharad season to mean the point of fall equinox was at the intersection of Karitka/Margashirsha, it lead us to the time of ~3000 BCE.
According to Vartak-Oak Hypothesis, Bhādrapada and Āśvina were part of Varṣā season and Kārttika and Mārgaśīrṣa were part of Śarad season in the time period indicated above . However, Oak’s analysis is based on first part of Suśruta Saṃhitā 1.6.10. Later part of the same passage tells a completely different story.
2. Phālguna in Vasanta season and Vaiśākha in Grīṣma season
Oak has chosen the statement from Suśruta Saṃhitā 1.6.10 that Bhādrapada and Āśvina were part of Varṣā season and Kārttika and Mārgaśīrṣa were part of Śarad season. Based on this cherry picking of evidence, Oak has claimed the dates of 3,000 BCE and 4,000 BCE as plausible dates for Suśruta. However, the same passage also says that Phālguna and Caitra were part of Vasanta season and Vaiśākha and Jyeṣṭha were part of Grīṣma season. If Oak had selected these combinations then the dates will belong to our times in his own scheme of things . Oak has made no mention of this clear contradiction in his Sangam Talks presentation .
Things get interesting here. Oak has collaborated with Mr. Sanket Kulkarni for research on Suśruta Saṃhitā. An article based on Kulkarni’s presentation contains the following statement and figures :
There is a peculiar problem with descriptions of seasons, somewhat unique to Sushruta Samhita.
Sushruta Samhita thus maintain 6 seasons. However the text does not explain what caused this change and does not explain the correspondence of its own seasons with that of standard list of seasons. Per this arrangement, the timing of Sushruta Samhita can be considered to be that of our times or may be about 2000 years ago. This then remains the limitation of dating effort based on internal evidence of Sushruta Samhita.
So here is acceptance that whatever Oak had presented in Sangam Talks  regarding the dating of Suśruta Saṃhitā was complete nonsense. So why did Oak present it then knowing it fully well that the passage contained conflicting information? Furthermore, Oak and Kulkarni cannot wash their hands of so easily by making such statement in the article. The article makes the case that the mixed up seasons from the passage Suśruta Saṃhitā 1.6.10 were the seasons during the time of Suśruta Saṃhitā, while the standard seasons are from other texts as seen in figures above. This is simply not true. The standard list of seasons is given in Suśruta Saṃhitā itself in the same chapter that the passage Suśruta Saṃhitā 1.6.10 is from. The article says that Suśruta Saṃhitā does not explain the correspondence of its own seasons with that of standard list of seasons. This is complete nonsense. The mixed up seasons from the passage Suśruta Saṃhitā 1.6.10 are recent insertion in Suśruta Saṃhitā. The list of seasons given in Suśruta Saṃhitā 1.6.6–7 is exactly same as the standard list of seasons. This is why there is no explanation why the seasons are different.
3. The standard list of seasons in Suśruta Saṃhitā
The text of Suśruta Saṃhitā 1.6.6–7 is as follows:
tatra māghādayo dvadaśa māsāḥ dvimāsikamṛtuṃ kṛtvā ṣaḍṛtavo bhavanti te śiśiravasantagrīṣmavarṣāśaradhemantāḥ teṣāṃ tapastapasyau śiśiraḥ madhumādhavau vasantaḥ śuciśukrau grīṣmaḥ nabhonabhasyau varṣāḥ iṣorjau śarat sahaḥsahasyau hemanta iti
ta ete śitoṣṇavarṣalakṣaṇāścandrādityayoḥ kālavibhāgakaratvādayane dve bhavato dakṣiṇamuttaraṃ ca tayordakṣiṇaṃ varṣāśaradhemantāḥ teṣu bhagavānāpyāyate somaḥ amlalavaṇamadhurāśca rasā balavanto bhavanti uttarottaraṃ ca sarvaprāṇināṃ balamabhivardhate | uttaraṃ ca śiśiravasantagrīṣmāḥ teṣu bhagavānāpyāyate’rkaḥ tiktakaṣāyakaṭukāśca rasā balavanto bhavanti uttarottaraṃ ca sarvaprāṇināṃ balamapahīyate
The English translation of the text is as follows :
The twelve months such as, Māgha, etc. are divided into six seasons such as, Winter, Spring, Summer, Rains, Autumn and Hemanta, each consisting of two months. The two months known as Tapas and Tapasya (Māgha and Phālguna) constitute the season of winter. Spring consists of two months called Madhu and Mādhava (Chaitra and Vaishāka). Summer is marked by two months known as Shuchi and Shukra (Jaistha and Āshādha). The rains or the rainy season is marked by two months called Nabhas and Nabhasya (Shrāvana and Bhādra). The two months known as Isha and Urja (Āshvina and Kārtika) constitute what is called the season of Autumn. Hemanta is marked by two months called Sahas and Sahasya (Agrahāyana and Pousha). These six seasons are respectively characterised by cold, heat, rains etc.
The two Ayanas are ushered in by the sun and the moon changing their respective courses in the heavens (passing over the tropics of Cancer and Capricorn) as the measures of time. The rains, autumn and Hemanta follow one another in succession when the sun is over the Tropic of Capricorn or is in the Winter Solstice (Dakshināyanam) and the moon gains in strength in this part of the year. Rasas (Serum or sap) possessed of acid, saline and sweet tastes, grow strong and become dominant when the sun is over the Tropic of Capricorn (Dakshināyanam) and all beings gain in strength and energy more and more. Winter, spring and summer mark the passing of the sun over the Summer Solstice (Uttarāyanam). The sun grows stronger in heat and light, and saps (rasas) of bitter, pungent and sour tastes increase in intensity, and all animals gradually begin to lose strength and energy.
Thus Suśruta Saṃhitā 1.6.6–7 provides the standard combination of seasons and months that we are familiar with. The passage also gives the position of solstices and equinoxes. This standard combination of seasons and months and the position of solstices and equinoxes are shown in Figure 3.
Oak has made no mention of Suśruta Saṃhitā 1.6.6–7, which clearly negates his dating of Suśruta in his own scheme of things. This passage together with Suśruta Saṃhitā 1.6.10 has been discussed in detail by Tilak in his book Orion , and anyone who does research in the dating of ancient Indian texts knows about the book Orion. Here is what Tilak has written about the seasons and months in Suśruta Saṃhitā :
The only other authority I can find for supposing that Phālguna was a Vasanta month is the statement in Shushruta’s medical work that “Phālguna and Chaitra make Vasanta.” But on a closer examination of the passage wherein this sentence occurs, it will be found to bear on its face the marks of a later insertion. There are two consecutive paragraphs in Shushruta, each enumerating and describing the seasons of the year. The first states that “There the twelve months, beginning with Māgha, make six seasons, comprising two months each. They are Shishira, &c… Of these Tapa and Tapasya make Shishira” and so on until all the six seasons in their usual order, the ayanas, the year and the lustrum are described; and at the end we have “this is called the wheel of time by some.” The second paragraph then begins with the words “But here” and continues to state “But here the six seasons are, — Varshā, Sharad, Hemanta, Vasanta, Grīshma and Prāvṛiṣh,” thus altogether dropping Shishira and dividing the rainy period into two seasons Varshā and Prāvṛiṣh. The paragraph then proceeds to assign the months to the seasons as follows:- Bhādrapada and Āshvina is Varshā, Kārtika and Mārgashīrsha is Sharad, Pauṣha and Māgha is Hemanta, and Phālguna and Chaitra is Vasanta; and so on until all the months are assigned to their respective seasons. The second paragraph, however, makes no mention of the ayanas, the year, or the lustrum. It is therefore evident that the writer of the second paragraph, whosoever he may be, wished to note that the seasons and their corresponding months mentioned in the first paragraph has ceased to represent the actual state of things in the writer’s time and province, and not thinking it desirable or possible to expunge or correct the old paragraph, he added immediately after it a second paragraph describing the seasons as he saw them. The words “but here” at its beginning, the assignment of four months to the rainy season, but under two different names of Prāvṛiṣh and Varshā, to keep up the old number of seasons, and the absence of any reference to the ayanas, the year and the lustrum described in the previous paragraph — all point to the conclusion that the second paragraph is of later origin and inserted with a view only to note the changes in the occurrence of events described in the paragraph next preceding it. It might be contended that the second paragraph is that of Shushruta, who notices the old order of things in the first. But I need not go into that question here. For in either case it is plain that the passage wherein Phālguna and Chaitra are assigned to Vasanta is the production of a later writer, whosoever he may be whether Shushruta or anyone else, and as far as our present inquiry is concerned we cannot take the passage as an authority for holding that Phālguna was a Vasanta month in the days of the Taittirīya Sanhitā. I may however remark, that Vāgbhaṭa who professes to summarise the works of Shushruta and Charaka gives the order and description of seasons as we find it in the first paragraph in Shushruta [Aṣṭāṅgahṛdaya Sūtrasthāna iii.1], without alluding to the changes noted in the second paragraph. We may, therefore, suppose that either the paragraph did not exist in Vāgbhaṭa’s time or that he did not regard it as genuine.
In a very logical manner Tilak makes it absolutely clear that the passage Suśruta Saṃhitā 1.6.10, part of which Oak has used selectively, is a later insertion. It did not exist in Vāgbhaṭa’s time or Vāgbhaṭa did not regard it as genuine. Vāgbhaṭa’s time is estimated to be between 400 CE to 600 CE . So the passage that Oak selectively quotes to prove an antiquity beyond 3,000 BCE for Suśruta is most likely inserted after 400 CE. It is not only a later insertion but also completely confusing. It has no Śisira season, which is a part of standard six seasons of Indian texts. It makes the list of six seasons by adding a new season Prāvṛṣa. However, Prāvṛṣa and varsā are identical in Indian literature.
“Prāvṛṣ and varsāḥ are the usual names of the monsoon.” 
The dropping of Śisira season and addition of Prāvṛṣ while keeping Varsā season is absurd. Thus the passage is not only a later insertion but also useless for dating. Oak has still misled people in believing that Suśruta Saṃhitā 1.6.10 can be used to prove greater antiquity for Suśruta. But what purpose does a date based on dubious evidence serve?
4. Contradictory evidences
As stated above, Oak selectively uses Suśruta Saṃhitā 1.6.10 to come up with dates of 3,000 BCE and 4,000 BCE. Oak then finds that this does not match his dating of Mahabharata to 5,561 BCE. Oak needs to take the date of Suśruta further back, so he stretches the dates to cover a wider range of 5,000 to 2,000 BCE :
If we perform sensitivity analysis by taking into account various sources of variations (Adhika masa, delaying of corrections to seasons/lunar months shifts, etc.) we may thus define this time interval to be a broad time interval of 5000 BCE through 2000 BCE.
Why did not Oak perform this sensitivity analysis before coming up with the dates of 3,000 and 4,000 BCE? Even 5,000 BCE is contradictory to his own dating of Mahābhārata to 5,561 BCE. Oak presents evidence from Suśruta Saṃhitā, Garuḍa Purāṇa and Mahābhārata to show that the timing of Suśruta was before Mahābhārata [reference 2 at t = 16:52 to t = 18:50, reference 3 at t = 2:40 to t = 6:00, reference 4]. As Oak has dated Mahābhārata to 5,561 BCE, Oak and Kulkarni conclude that the date of Suśruta was earlier than 5,561 BCE :
Sage Sushruta is described as existing prior to this timing of the Mahabharata war. Thus, Sage Sushruta existed before 5561 BCE or long before 5561 BCE!
However, this is in contradiction to Oak’s own scheme of things as lunar months should have moved by two months in 5,561 BCE compared to seasons from the standard list. According to Oak, Māgha and Phālguna were in Hemanta season in 5,000 BCE . However, according to Suśruta Saṃhitā 1.6.6–7, Māgha and Phālguna were in Śiśira season. Clearly, Suśruta Saṃhitā cannot be as old as 5,561 BCE in Oak’s own scheme of things.
I have referred to Oak’s scheme of things in this article and named it “Vartak-Oak hypothesis”. What is it? What is its basis? What is its validity? Is there evidence for it? Are Oak’s highly touted astronomy poison pills really poison pills? I will answer all these questions and refute each astronomy poison pill pertaining to Rāmāyaṇa in my next series of articles on the refutation of Nilesh Oak’s astronomical dating of Rāmāyaṇa to 12,209 BCE.
1. Tipton, C. (2008). “Susruta of India, an unrecognized contributor to the history of exercise physiology”. Journal of Applied Physiology. Vol. 104 (6), pp. 1553–1556.
2. Fascinating Validation Of Sushruta Samhita | Nilesh Oak | #SangamTalks. https://www.youtube.com/watch?v=AIuKuYZ-bd8.
3. Sushruta & his Samhita — P9 — Sushruta graced Bharat 7500 years ago!. https://www.youtube.com/watch?v=jvHqPKyfLyg.
4. Sushruta and his Saṃhitā — Part 9 — Sushruta graced Bharat atleast 5561 BCE!. https://medium.com/@mitra/sushruta-before-5561bce-34b7155a93bb.
5. Vartak, P.V. (2004). “The Scientific Dating of the Mahābhārata War”, Veda Vidnyāna Mandala: Pune, India, 2nd revised edition, pp. 17–18.
6. Oak, N.N. (2011). “When did the Mahabharata War Happen?: The Mystery of Arundhanti”, Bhim: USA, p. 39.
7. Bhishagratna, K.K.L. (Editor) (1907). An English translation of The Sushruta Samhita based on original Sanskrit Text, Vol. 1-Sutrasthanam. Calcutta: Kaviraj Kunja Lal Bhishagratna, p. 48.
8. Tilak, B.G. (1893). “The Orion”. 1987 Reprint. New Delhi: Cosmo Publications, pp. 64–67.
10. Bhishagratna, pp. 46–47.
11. Subhaktha, P. K. J. P., Gundeti M.S., Narayana, A. (2009). “Vagbhata — His Contribution”. Journal Ind. Med. Heritage. Vol. 39, pp. 111–136.
12. Feller, D. (1995). “The seasons in mahakavya literature”. Delhi: Eastern Book Linkers, p. 15.
13. Oak, N.N. (2014). “The Historic Rama”, (Publisher not mentioned in the book), p. 192.
Note: April 24, 2021
Following the publication of this article, many insulting comments were made on Twitter by Oak and his followers. Here is one example:
Oak is telling this to a scientist who has earned his engineering degree from IIT Kanpur and Ph.D. in Materials Science and Engineering from The Ohio State University, USA. The scientific acumen of Oak can be judged from this article and my previous article on Sūrya Siddhānta. Logical reasoning capability of Oak can be judged from his citing of poetic expressions as astronomical observations. A tweet by a precocious young man summarizes the reactions from Oak and his followers. Here it is with my comment:
Oak also wrote email responses in Google group भारतीयविद्वत्परिषत्, but didn’t respond to the two main points raised in this article:
1. Oak knowingly misled people in his Sangam Talks [Fascinating Validation Of Sushruta Samhita | Nilesh Oak | #SangamTalks. https://www.youtube.com/watch?v=AIuKuYZ-bd8 at t = 15:50 to t = 16:50]. He knew that Suśruta Saṃhitā 1.6.10 has conflicting information which negates what he was talking. Will an intellectually honest researcher do that?
2. Oak didn’t quote Suśruta Saṃhitā 1.6.6–7, which clearly states the standard list of seasons. In Oak’s scheme of things shown below, this combination of lunar months and seasons was valid between 1500 BCE and 500 CE, which is in clear contradiction to his dating of Suśruta to earlier than 5,561 BCE.
More about the author
I am a seeker in search of the true history and heritage of India. I have strong scientific background (B.Tech. in Metallurgical Engineering from Indian Institute of Technology, Kanpur and Ph.D. in Materials Science and Engineering from The Ohio State University, USA) and a deep interest in ancient Indian texts. My work on Indology spans three different fields: cosmology, astronomy, and history.