Consider the following assertion : In the Pleistocene period either the Yamuna once flowed into the Indus, or the Sutlej flowed into the Yamuna and one major tributary of either had shifted from the Ganga to the Indus or vice versa. Which of the following is/are the basis of the above assertion ? 1. The Nadi-Sukta of the Rigveda 2. The explorations of the Sutlej and the Yamuna by Robert Bruce Foote 3. The presence of the same species of dolphins in both the Indus and the Ganga river systems Select the answer using the code given below :
- (a) 1 only
- (b) 2 only
- (c) 1 and 2
- (d) 3 ✓ UPSC's answer
Why the answer is (d)
• The assertion is a geological one about Pleistocene river capture between the Indus and Ganga systems, so its basis must be physical or biological evidence.
• The freshwater river dolphin Platanista occurs in both the Indus and the Ganga–Brahmaputra systems; a species cannot cross a watershed, so the two basins must once have been connected — this is the classical argument (evidence 3).
• The Nadi-Sukta of the Rigveda merely lists rivers in order; it is a hymn, not evidence of ancient drainage change.
• Robert Bruce Foote was a geologist and pioneer of Indian prehistory (Palaeolithic finds at Pallavaram), but he made no such exploration of the Sutlej and Yamuna as the basis of this assertion.
• Hence the basis is evidence 3 alone.
Why the other options are wrong
- (a) 1 only
- The Nadi-Sukta is a hymn listing rivers, not evidence of drainage change.
- (b) 2 only
- Foote's work was on Palaeolithic tools, not on Sutlej-Yamuna drainage.
- (c) 1 and 2
- Neither the hymn nor Foote's explorations support the geological assertion; the dolphin evidence does.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2026, held on 24 May 2026. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.