According to Mahabharata, Puranas and many sources, it is assumed that Pandavas and Kauravas were more than 80 years old when Kurukshetra battle was fought. A detailed discussion on the calculation of ages from different sources can be found here. But how can one fight a deadly war at this age with perfection as shown by the warriors from both the sides? I believe that anything super natural in Mahabharata is written in symbolic way and if we research more, the technical and actual incident can be extracted. So, what exactly does this age group symbolize when octogenarian heroes can fight such a historical battle, as per Hindu Scriptures or from Hinduism pov?
As already discussed in the answer here, Vedas clearly declare 100 yrs. Of age to Humans. But this is for normal Human Body. Vedas also declare that it is possible to live long age by making the body purified by the fire of Yoga. Eg. Svetasvatara Upanishad in 2.12 states:
पञ्चात्मके योगगुणे प्रवृत्ते ।
न तस्य रोगो न जरा न मृत्युः
प्राप्तस्य योगाग्निमयं शरीरम् ॥ १२॥
When the fivefold perception of Yoga, arising from (concentrating the mind on) earth, water, light, air and ether, have appeared to the Yogin, then he has become possessed of a body purified by the fire of Yoga, and he will not be touched by disease, old age or death.
Thus, as suggested by the above verse one can attain body purified by fire of Yoga (Prãptasya Yogãgnimayam Shariram). And when the body is purified by fire of Yoga it is free from illness, oldage and death (Na Tasya Rogo Na Jarã Na Mrityu).
During the Mahabharata period there were many mystic and yogic sages like Vyasa, Parashara, etc.. and the warriors who fought Mahabharata war had also powerful Yogic persons as their Guru. So, they certainly purified their body by the fire of Yoga to some level. So, they were able to fight Mahabharata war easily being octogenarian also.
Patanjali Yoga Sutra in 3.47 states:
The glorifications of the body are beauty, complexion, strength, adamantine hardness.
In the commentary of this Sutra Swami Vivekananda states:
The body becomes indestructible; fire cannot injure it. Nothing can injure it. Nothing can destroy it until the Yogi wishes. “Breaking the rod of time he lives in this universe with his body.” In the Vedas it is written that for that man there is no more disease, death or pain.
Yes, it's indeed wonderful to think about 85+ years of people fighting during the Mahabharata with such a fierce war. Few points:
SAtvika food habits, cleaner environment, exercise rituals, Yogic culture -- can be attributed for such stronger bodies at 80+ years.
Like other answers, We can assume that the people of those times would be eating sAtvika food and performing Yoga. Here is a source:
BG 17.8 - Foods that increase life, firmness of mind, strength, health, happiness and delight, and which are succulent, oleaginous, substantial and agreeable, are dear to one endowed with Sattva.
Comparing current time, the pollution and good adulteration has increased. It's quite possible that during Mahabharata times such issues would not have persisted
On the contrary, even in today's time, it's possible to many instances of super human abilities; e.g. Samruai warriors of Japan, certain martial artistes; In such case today & ancient Mahabharata times are comparable
Earlier due to stronger division system, the marriages use to happen within same gotra/castes of Kshatriyas. Which helped the genetic print of their children to become stronger with every passing generation. Such gene pools may or may not retain when people marry in hybrid fashion in modern times.
Opposing argument: According to the sources the majority of the main characters were beyond 85 years. Despite that, there is no mention about the regular soldiers. In comparison of all the warriors (Kurus + Kings + Soldiers + ...), such handful of main characters can be simply discounted as special cases.
Like other classes held by their Gurus. It is mandatory to become a YOGI for them and YOG was a routine practice for people of those days. Now if you have read Holy Book of Hinduism
Geeta, there at one instance Krishna referred Arjuna as
Kshatriya not because he belongs to that clan or caste. It is because he is that level of
Yogi. As Krishna clarifies "Arjuna ek Kshtriya shreni ka yogi hai".
Also this is the reason they are able to call super powers exists in our Solar system. Proof of this has been seen later years also. Tansen's deepak rag, Swami Dayanand Saraswati victory over death (he died because he wanted to). These people are yogi, they can control the rear and tear of cells formation in their body. Now a days few animals can do so, they have the ability to regrow their body parts several times in their lifetime.
But people now a days won't believe it because they can't do it or they have never noticed such thing in their life by naked eyes.
But how can one fight a deadly war at this age with such perfection?
80-year-olds fighting fierce battles is simply not possible especially when they are nearing the end of their 100-year lives.
Some of the answers to What was the age of all Pandavas during the Mahabharata war? also talk about Bhishma being 140 years old when he died which cannot be true either.
The Yajur Veda at several places § clearly suggests the normal human life is less than 100 years. As you can see below some of the hymns are prayers to Gods to grant men and women 100 years. Only yogis are capable of living for full 100-year lengths.
XIX. 37. May fathers, full of glory and mental peace, purify me with a pure life of a hundred years. May grandfathers, purify me with a pure life of a hundred years. May great grandfathers purify me with a pure life of a hundred years. May learned and calm grandfathers purify me with a happy, pure life of a hundred years. May sedate great-grandfathers purify me with a pure life of a hundred years. May I obtain full length of life.
XIX. 46. My folk yet living among those who live, are of one mind and similar attributes. On me be set their wealth through a hundred years in this world.
XIX. 93. Just as a woman devoted to yoga, engrossed in deep meditation, practising the limbs of yoga puts her soul in contemplation, so should husband and wife free from disease like a good physician, practise the parts of yoga and attain to the beauty of supremacy. As men practising yoga live for a hundred years, so should we, full of happiness, realise the immortal nature of the soul.
XXV. 22. O learned persons, may we live in your company for a hundred years. Let not our bodies decay before that period, in which old age our sons become fathers in turn. Break ye not in the midst our course of fleeting life.
Sītā in this verse from Vālmīki Rāmāyaṇa hints that a man normally survives only for a hundred years:
कल्याणी बत गथा इयम् लौकिकी प्रतिभाति मे | एहि जीवन्तम् आनदो नरम् वर्ष शतात् अपि || ५-३४-६
6. aanandaH = joy; eti = rushes; jiivantam- to surviving; naram = man; varSashataadapi = even though (it be) at the end of a hundred years; iyam = this; laukikiir = wordly; gaathaa = adage; pratibhaati = appears; kalyaaNi = auspicious; maa = to me.
'Joy rushes to surviving man even though (it be) as the end of a hundred years' - this popular adage appears true and and auspicious for me.
Īśāvāsyopaniṣad, verse 2 also states the same:
कुर्वन्न् एवेह कर्माणि जिजीविषेच्छतं समाः ।
एवं त्वयि नान्यथेतोऽस्ति न कर्म लिप्यते नरे ॥ २ ॥
kurvann eveha karmāṇi jijīviṣecchataṃ samāḥ |
evaṃ tvayi nānyatheto'sti na karma lipyate nare || 2 ||
2. Always performing karma here, one should desire to live, for a hundred years. So long as thou (seekest to live) a mere man, no other (path) exists (where) activity does not taint thee.
Kurvanneva = always performing. iha = (here) karmāni = rites such as agnihotra. jijīviṣet = one should desire to live. śatam = one hundred in number. samāḥ = years. For thus much is known to be the maximum age of man. Since (this is) a (mere) iteration (of an empirically known fact) what should be taken as enjoined (here) is that, if one should desire to live a hundred years, he should live only performing karma. evam= in this manner. in regard to you), nare i.e. when you live content to be a mere man. itaḥ i.e., from this present course of performing karma like agnihotra. different course, na asti =does not exist; in which course evil action does not stain; i.e., you do not get tainted by sin. Wherefore if one should desire for life Tone should live) throughout performing karma such as agnihotra prescribed by the śāstra.
Swami Vivekananda offers his opinion on this topic in his lecture The Religion We Are Born In:
In the Puranas we find many things which do not agree with the Vedas. As for instance, it is written in the Puranas that someone lived ten thousand years, another twenty thousand years, but in the Vedas we find :— "Man lives indeed a hundred years."
Which are we to accept in this case? Certainly the Vedas.
§ The only exception is hymn III.62 which suggests some sages can lives 3 times as long as normal humans:
III. 62. May we be endowed with triple life, as a truth-seer sage, or the custodian of knowledge through the grace of God, is endowed with, or as the learned persons enjoy triple life.
One user below commented:
But how does this answer the question? You are (only) supporting that Man cannot live beyond 100 years.
I'm answering by way of negating the premise of the question that several prominent characters (the Pandavas, Bhishma etc.) involved in the Mahābhārata war were in their 80's or 90's and yet they are hale and hearty to engage in a full-blown war. All my citations above attest to the fact from the Vedas that most people simply don't live beyond 100 years. And by common sense, any person or living being which is nearing the end of its life simply cannot have the stamina to engage in several battles during the course of an 18-day war.
As evidenced here, the Mahabharata occurred in the Dvapara Yuga.
This is what the Manu Smriti says about length of life:
1.83. (Men are) free from disease, accomplish all their aims, and live four hundred years in the Krita age, but in the Treta and (in each of) the succeeding (ages) their life is lessened by one quarter.
The optimal lifespan in Dvapara Yuga is 200 years of age. Therefore, the Pandavas and Kauravas could live up to 200 years of age due to different Yuga Dharma.
Note: this verse is interpreted differently by Medhatithi. To reconcile with the Chhandogya Upanishad verse (3.16.7) that he cites and his commentary, there is another way to interpret this Manu Smriti verse.
‘Quarter’—the term ‘quarter’ here does not stand for the fourth part, it stands only for part; the meaning being that ‘man’s life becomes shortened in part’, i.e. some die while they are young children, others on reaching youth, and others on attaining old age; and the full span of life is difficult to attain.
The Pandavas and Kauravas would have found it easier to reach the full lifespan than us because they were in the Dvapara Yuga. Therefore, they could most likely have lived longer and could have fought the war at their age.
The premises of this question assumes that most of the main warriors were 80+ years. However in reality, most of them were in their 40s (or early 50s at the max).
Except Drona, Bhishma, Drupada hardly there can be any warrior, who were in their 80s. Drona's age (85 yr) & based on it others' age is discussed in this answer.
However it does say that Drona had shown swiftness like a 16 years old during his last day. So that also means that 80+ years, was still a good age to fight. Now that could be possible mostly due to food habits & abstaining from sex & other sense fulfillment. From Gita, Satvik way of life is suggested to be giving longitivity.