human evolution and yugas?

According to religious book Rig Veda - Life on earth is governed by cosmic energies that originate from a single godly source. There are theories which state the Universe, the planetary systems and living organisms were created on earth at the start of the four Eras or Yugas. At the end of the fourth yuga, the cosmos is dissolved to be recreated once again from scratch. Living beings undergo the process of birth, growth, decay and death, not just bodily, but at the level of consciousness. The soul in an animal body may not be evolved to be able to identify the meaning of inner consciousness. The soul works is a BlackBox that holds the balance of karmas from the previous births as it evolves into higher consciousness. When it becomes like the Supreme consciousness, it merges with it. As per scientific calculations, the cycle of human civilization advance and decline is predicted to be around 25,900. Manu Samhita places the age of civilization at 24,000 and some Vedic astrologers place it at 25,920 years. The ages have been divided in the Golden, Silver, Bronze and Iron as per ancient astrology, and the same idea can be found in Greek and Hindu texts which divides the human evolution eras into four – Sat ( the Age of truthfulness or the fourth), Treta( the third one), Dwapara ( the second) and Kali ( the first). Manu age of the universe The duration of each era or age - was fixed by Manu as 4000 years, 3000 years, 2000 years and 1000 years plus the traditional period which is one-tenth of the respective length before and after, this means, Sat yuga duration is 4800 years, Treta is 3600 years, Dwapara is 2400 and Kali is 1200 years – the four age total make 12,000 years. The two cycles of 12,000 years make one complete cycle, where the first 12K years make the ascending half when the sun is moving towards the point of orbit close to the galactic centre, and the last part make the descending half when it is moving towards the last degrees of the galactic centre. What is the current age as per Hindu texts? Some theorists assume descending kali yuga ended in 499 AD and the ascending Kali yuga started in 499AD that lasted till 1699AD. Now the human civilization is undergoing the ascending dwapara yuga that will end 4099 AD. Others believe, we are undergoing the last phase of Kaliyuga, which will end in some years and then we may enter sat yuga. Most calculations are based on interpretation of the Sanskrit verses of Vedas. The literature widely mentions about the lifestyle and beliefs in the four eras. It is said the human intelligence and their physical strength reduce to one quarter after each passing descending era. Sat Yuga is about 100 per cent intelligence, purity of thoughts and Kali-yuga is about 25% of purity and human intelligence. Dharma - spirituality and connectivity to the supreme consciousness is 100 per cent in sat yuga and it declines to zero at the end of Kali-yuga.