There was a Natural Scale in the West as well, and was called as the 'Just Intonation Scale'. This was named as "just" because, the scale (or Saptak) was 'just' (or correct) only in 1 note (or 1 Shadja). This scale was used in Medieval music in Europe from AD 550-1450. The Western music up to the 16th century employed this scale to sing, and to tune their instruments at that time, namely, the Harpsichord, and Clavichord.
With the advent (or worldwide invasion) of the '12-Tone-Equitempered scale', this older but more natural scale has now become history. The same thing happened in India too. Since the availability of Harmonium and Organs from 1860s, the Indian natural scale of 22 Shrutis was forgotten and left behind due to over-dependency on ET tuned Harmoniums.
The above table shows that these 16 notes were known for centuries and we shall see later that all these are a part of 22 Indian Shrutis.