Rig Veda is the oldest literature of mankind.
It has 25 recensions (sakhas). Only five are now available known as Saakala , Bhaashkala, Saankhyayana, Ashwalaayana, Kousheethakee saakhas.
The recensions have only small variations. There are 397,265 letters, in 193,816 words, in 10,552 stanzas (hymns), in 2,024 vargas, in 64 chapters, compiled as 8 ashtakas or 10 mandalas of rigveda.
It is brought from the Rigs which are otherwise known as Stanzas or Lines. These stanzas are compiled into 2,024 Classes or Vargas.
Lots of speculations have been done on when Rig Veda was written. The most authentic timeframe as computed by historians in Scotland, found a verse which says, translates as “When Jupiter crossed Thishya Star, it felt like the birth of the Thishya Star”. As per this verse when the astronomers back calculated the time for this occurrence,they saw that this might have occurred 4275 ± 75 BC. The verse from which this is derived is from the 10th Mandala of Rigveda. This means that the last of the Rigveda was written in this time. So ultimately, it is very much visible that First parts of the Rigveda would have been written about 1000 years before the 10th mandala, which is about 5275 yrs ago.
Hereby you can see that the Oldest Mankind scripture was classified very much like the modern texts.
The Rigvedas, give information on Historical, cultural, sociological, scientific and a variety of other subjects.
Courtesy: www.iish.org