First of all, the lecturer states that it is hard to say that the downfall of the Harappans were caused by outside invaders as there is no physical evidence that supports this claim. The lecturer points out that it was not just single town that disappeared but 100 other towns and there is no archeological evidence found in these areas. All these claims given in the lecture directly contradicts the assertion made in the reading that some evidence found supports the idea that there were battles in the region and the Harappans were taken over by outside invaders.
Secondly, the lecturer indicates that rather than the wipe out of the Harappan civilization, it should have caused thrive in growth of the civilization. The speaker emphasizes that the Egyptian and Mesopotamian were sharing same environment and Egyptian and Mesopotamian were able to grow more rapidly so Harappan civilization also should have had thrived. This particular viewpoint of the speaker without deviation challenges the point put forth in the reading that the change in climate and nature like lack of rainfall creating desertification of the farmland which in turn caused famine in the area.
Finally, the lecturer contends that Cholera is only caused due to drinking polluted water but the Harappan civilization had water system which guaranteed them access to clean water. The lecturer highlights that they also had sewer system to keep the dirty water away to prevent any contamination of the water. This argument presented in the lecture surely opposes the idea proposed in the reading that because Cholera spreads through water, it is very likely for the people of the Harappan civilization were affected by it as they all used the same water