To drink or not to drink

[Rob Furness]

So they needed to be able to keep going when it was asked of them, by keeping topped up

That's not really evolution. But surely the same applies to dogs as it does to us, using energy would liberate water and thus they wouldn't need to keep topping up. Presumably they do it for comfort, same as us really.

Of course we usually know how long we will be out for, and can plan accordingly. Military scenarios, where we know we don't know how long we will be out, are different, and the keeping topped up strategy applies there as well.

That's not really evolution either. Evolution is not a conscious process and isn't really affected by choices such as that, evolution would come into play if our ancestors regularly needed water but weren't able to top up, and thus the ones who were able to survive better with less water would be the ones to carry the genes on.