The concept of the four yugas implies that there have been a number of cycles (six to be precise) through which creation and perhaps humanity has moved and has subsequently collapsed. The present cycle is the seventh one and is of 12000 years according to the Manu Smriti as well as the Mahabharata. So if we take the Satyuga to be about 4800 years then the Ramavtar would be roughly around 7200 years ago and Sri Krishna Avatar about 4000 years ago which more or less goes with our present estimate of time. The Satyuga itself would be roughly 10000 or 12000 years ago.
Now if we read the description of the humanity around the Ramavtar we see that there were three main types of human types. There were the Vanaras which were a higher type of apelike humanity (not ape but a transitional type from Ape to human). The second type was the Rakshasa and the Asura that seems to have vanished without a trace. The third, that not only survived but evolved into the modern man was the human proper known for his intuitive sense of dharma. This description runs quite close to the findings of anthropology if we look below the apparent facts, apparent because there is no accurate way of knowing exactly what these beings were except, to an extent, their physiognomy. This humanity as we see described in the Ramayana was closer to the earth (Sita Mata is bhoomija) and hence more in contact with the physical intuition which acted directly without the intervention of the complexities into which our mind has entered presently.
Satyuga Avatar is Parashuram. Humanity in that age is much more intuitive because the mind has not yet fully taken over. It is pure in its simplicity, strong in its physical being. It knows about things through a direct inner contact. Humanity in Satyuga is good because it lives by the dharma manifested in the heart without going through the complexities of the human mind. They are in direct contact with nature through their inner consciousness and hence they develop the intuitive sciences and an intuitive world view and self view without the need of philosophising. Put very simply they lived by the truth in their heart and soul and hence carried a charm and beauty as we do not find in a later highly mentalised humanity. Since this layer of humanity developed in and around India we have its traces and stories. But this does not mean that everyone was good and lived by truth. The rakshasa and the animal type was there and there are stories of how Parashuram had to fight them out 21 times to free the world of the menace of Rakshasa kings until the Rakshasa was taken up by the Asura (as we see in Ravan), the animal type was taken up into the Vanara (as we see in Vali and Sugriva) and the human living by the truth in the heart was taken up by a more illumined mentality as we see in Lord Rama and his brothers. That is the time when the Age of the Vedas changes into the Age of the Upanishads with debates in the assembly of kings about the truth of things. The king here becomes the upholder of dharma while the common man trusts his word.
Then comes Dwapara and here the mind begins to develop its complexity and begins to govern the vital nature by codifying. Direct contact with the Dharma is lost and is replaced with rules and regulations. God vision is replaced by God discussion and spiritual philosophy. The Asura uses the mind to justify its ambitions. Finally the complete breakdown of Dharma takes place in a completely mind centered civilization. This civilisational fall due to the development of the mind is the essence of the story of Adam and Eve and their fall from Paradise and the innocence.
Yet this was needed since the direct intuition of the heart has to now come from the highest regions of the intuitive mind. Besides the passage through the mind has led to a high degree of individualisation which is also a needed step. Else man was governed by the social norms. Now he must find the dharma within him. Passing through mind man will climb to the new Satyuga but this Satyuga will be much higher and greater than the Satyuga of yesterday due to the complex challenges mankind has passed through.
Hope this answers your question.
Affectionately
Alok Da
