The bare mininum intake of water should be at least 64 oz. Now if you live in hotter states like me who live in AZ in the summer months you will want to increase that intake to about 96-128 oz per day. Of course your activity level and how much you spend outside will be a factor as well.
Neanderthals were a separate species from modern humans, and became extinct (because of climate change or interaction with modern humans) and were replaced by modern humans moving into their habitat between 45,000 and 40,000 years ago.
Hence, Neanderthals and fully modern humans may have overlapped for as much as 10,000 years in Europe. Again, with fully modern humans on the scene, it is not necessary to have Neanderthals evolve into modern humans, further bolstering the view that humans replaced Neanderthals.