Those hominids that survived had what's now known as the "uricase mutation", something that caused them to react to fructose to both store fat and downregulate cellular energy consumption (animals that go long periods without eating have it too).
IMO it's a fascinating mechanism, but the TL;DR of it is that this is what makes fructose in large quantity (particularly as a 'surge', which would come with soft drinks) so bad for us. On a mobile, so no links, but google 'Rick Johnson Uricase Mutation' for details on how this works.