As several people in this thread have stated, without a definition of the term “smarter” the whole premise of the thread lacks any sort of objectivity from a scientific standpoint. That, however, has never stopped us from discussing things based on our own views and opinions and is unlikely to do so anytime soon.
Do animals make decisions? Absolutely. Animals make decisions constantly. Whether those decisions are based on instinct, or some form of learned behavior, could be up for discussion, but that must be taken in a case-by-case basis and is the same with humans.
I worked for many years training dogs, and a great deal of it involved behavioral modification.
The one thing that dogs lack, that humans do not, is the ability to chain together logical associations (or assumptions) based upon previous experiences (memory). Here is something I ran into with dog owners on a somewhat regular basis when helping them modify their dog's behavior.
A) Fido gets into the trash and makes a mess when the owner is gone.
B) The owner comes home and finds the mess.
C) The owner reprimands the dog for making a mess.
D) Dog slinks away after being scolded, so owner assumes Fido “knew he did something wrong.”
This is completely false. Fido does not, and never will, make the association that A caused C, and therefore resulted in his response in D. All Fido knows is that if garbage is on the floor when his owner gets home he will get reprimanded. Many owners argued (and had completely convinced themselves) that Fido knew he did wrong due to his resultant actions. The simple way to prove them wrong was to ask them to call Fido over to the garbage and knock it over in front of him. Fido would ALWAYS slink away knowing he would be reprimanded for the spilled garbage even though, in this case, he was not the cause of it. All Fido knows is that B results in C, and he never makes the logical leap of association that A was the catalyst in the event which resulted in the scolding.
One, of course, can train the dog to stay out of the garbage by reprimanding it when caught in the act (or by setting a trap in the garbage to dissuade the behavior), but that is by no means the same as thinking the dog actually is associating its behavior with the outcome in a chain of events.
Is this sort of logical associative chaining of events exclusive to humans? I have no idea, but it is rather thought provoking and can easily be tested with your favorite domesticated furball.
As for humans being self destructive, all animals have the capacity to kill each other. Usually it involves a territorial dispute, but there have been cases of seemingly random, or wanton, killings with animals too. Due to our ability to use tools we’ve just become a lot more efficient at it.