If frozen water were less dense than liquid water then it would sink, rather than float. The biggest impact of this would of course be in bodies of water where the frozen ice would rest at the bottom of lakes, rivers, etc. rather than floating on the top.This would be devastating to the life in these bodies of water who would not be able to survive in these conditions. There is also the fact that if ice sunk to the bottom, it would take longer to thaw completely, meaning that much of the water sources found in climates that experience a period of coldness would never thaw completely. It would be devastating to the existing ecosystems.
The purines-adenine and guanine
There appears to still be a lot of debate within science over whether humans or climate change were primarily responsible for the extinction of many of the large mammals during this period. One hypothesis supporting the link to early human hunters is that large animals in sub-Saharan Africa co-evolved with humans as they learned how to use tools and developed ever more effective weapons. When early humans moved into Europe and Asia, taking with them their weapons and hunting skills, the populations of large animals in those areas were not accustomed to human hunting, and were therefore easy prey.
