On each passing year there's something new. The past is gone, we are not living there. The thing that matters is how much we have learnt from our past. Only then we can explore new possibilities. The mind repeat what the heart can not delete. Same way each Yuga has it's own importance and people from that time zone should not be compared with people with another time zone. Each Yuga has it's own way of perceiving knowledge and ways to implement it. Here Bhai Gurdas Ji in Vaar 1, pauri 5 of 49 explained the way each of 4 Yugas were created and what was the most influential thing of that time.

1. The Yugs
ਜੁੱ ਗ ਆਦਿਕ
Vaar 1, Pauri 5 of 49

2. ਚਾਰਿ ਜੁਰਗ ਕਰਿ ਥਾ਩ਨਾ ਸਰਿਜੁਗ ਿਰ੃ਿਾ
ਦੁਆ਩ਿੁ ਸਾਜ੃।
The four Ages (yugs) were established and the first
three were given names Satyug, Treta, Dvapar.
4 Yugs
Satyug
Treta
Dvapar
Kaliyug
ਚਉਥਾ ਕਰਿਜੁਗ ਥਾਰ਩ਆ ਚਾਰਿ ਵਿਰਨ ਚਾਿੋਂ ਕ੃ ਿਾਜ੃।
ਬ੍ਰਹਮਣ, ਛਿਰੀ, ਵ੄ਸ, ਸੂਦਰ, ਜੁਗੁ ਜੁਗੁ ਏਕ੅ ਵਿਨ ਰਬ੍ਿਾਜ੃।
Fourth one was Kaliyug and four castes came to be
known as the kings of four ages. Brahmin, kshatriya,
vaishya and sudhra became predominate in each age.
ਸਰਿਜੁਰਗ ਹੰਸ ਅਉਿਾਿੁ ਧਰਿ ਸ੅ਹੰ ਬ੍ਰਹਮ
ਨ ਦੂਜਾ ਩ਾਜ੃।
In Satiyug, Vishnu is said to have come to earth as
Hans-avtar and explained the problems pertaining
to metaphysics and nothing but one soh(n)-Brahm
(Only One God) was discussed and pondered upon.
ਏਕ੅ ਬ੍ਰਹਮੁ ਵਖਾਣੀਐ ਮ੅ਹ ਮਾਇਆ ਿ੃
ਬ੍੃ਮੁਹਿਾਜ੃।
Getting indifferent to maya, people would praise
one Lord.
ਸਦਿਜਦਗ

3. ਕਿਰਨ ਿ਩ਰਸਆ ਬ੍ਰਨ ਰਵਖ੄ ਵਖਿ
ਗੁਜਾਿਰਨ ਰ਩ੰਨੀ ਸਾਗ੃।
They would go to forests and pull on life by
eating natural vegetations.
ਿਖ ਵਰਿਿਆ ਦੀ ਆਿਜਾ ਕ੅ਠੇ ਕ੅ਰਿ ਨ ਮੰਰਦਿ ਸਾਜ੃।
Though they lived for lacs of years but they would not
construct the palaces, forts and grand mansions.
ਇਕ ਰਬ੍ਨਸ੄ ਇਕ ਅਸਰਥਿੁ ਗਾਜ੃ ॥੫॥
On the one hand the world was passing away and
on the other the life current would go stably.
ਸਦਿਜਦਗ

4. ਿਰ੃ਿ੃ ਛਿਰੀ ਿੂ਩ ਧਰਿ ਸੂਿਜ ਬ੍ੰਸੀ ਵਰਿ ਅਵਿਾਿਾ।
In Treta in the Sun-dynasty descended in the
form of the kshatriya (Ram) a great incarnation.
ਨਉ ਰਹਸ੃ ਗਈ ਆਿਜਾ ਮਾਇਆ ਮ੅ਹੁ ਅਹੰ ਕਾਿੁ ਩ਸਾਿਾ।
Now the nine portions of age lessened and illusion,
attachment and ego inflated.
ਦੁਆ਩ੁਰਿ ਜਾਦਵ ਵ੃ਸ ਕਰਿ ਜੁਰਗ ਜੁਰਗ
ਅਉਧ ਘਿ੄ ਆਚਾਿਾ।
In Dvapar, Yadav-dynasty came to the forefront i.e.
the incarnation of Krishna became known to the
people; but because of the lack of good conduct, Age
by Age, the life span(of man) went on decreasing.
ਰਿਗ ਬ੍੃ਦ ਮਰਹ ਬ੍ਰਹਮ ਰਕਰਰਿ ਩ੂਿਬ੍
ਮੁਰਖ ਸੁਭ ਕਿਮ ਰਬ੍ਚਾਿਾ।
In the Rigveda, the conduct of the brahmin and the
ideas about the actions done facing the East were
discussed.
ਿਰ੃ਿਾ,
ਦੁਆ਩ੁਰਿ

5. ਖਿਰੀ ਥਾ਩੃ ਜੁਜਿੁ ਵ੃ਰਦ ਦ੃ਖਣ ਮੁਰਖ ਬ੍ਹੁ
ਦਾਨ ਦਾਿਾਿਾ।
Kshatriyas became related to the Yajurveda and
started pouring charities while facing the South.
ਵ੄ਸੋਂ ਥਾਰ਩ਆ ਰਸਆਮ ਵ੃ਦੁ ਩ਛਮ ਮੁਰਖ ਕਰਿ ਸੀਸੁ
ਰਨਵਾਿਾ।
The vaishyas embraced the Samaveda and bowed to
the West.
ਰਿਰਗ ਨੀਿੰ ਬ੍ਰਿ ਜੁਜਿ ਩ੀਿ ਸਵ੃ਿੰਬ੍ਰਿ
ਕਰਿ ਰਸਆਮ ਸੁਧਾਿਾ।
Blue dress for Rigveda, yellow for Yajurveda and
for singing of the hymns of Samaveda wearing of
the white dress became a tradition.
ਰਿਰਹੁ ਜੁਗੀ ਿਰ੄ ਧਿਮ ਉਚਾਿਾ ॥੬॥
Thus three duties of the three Ages were
enunciated.