Again and again I repeat, Many kinds of birds can fly, many kinds of fish that can swim, but no other kind on earth can walk like humans, no other kind think to study and invent like humans ....etc, You only refuse such fact because you do not accept the notion that God exists.
It seems that you cannot conceive of a person recognizing that man has been gifted with remarkable abilities including intellect, language, culture, civilization, and more, without concluding that those gifts must have come from an intelligent designer. People disagreeing with you are not disagreeing that humankind is very impressive. They just don't agree that these distinctions argue for a god more than a blind, naturalistic processes.
When we tell you that we don't believe in gods because we lack sufficient reason to do otherwise, you might consider that it is the truth, and not some excuse to run from God as you seem to believe. How did you rule out that we mean what we say - we find no reason, including the nobility and striking achievements of mankind, to believe in gods?
Why only humans have superior brains, was it a disadvantage for other animals to evolve with super brains?
That's a very good question.
Asking it doesn't establish a supernaturalistic answer, nor eliminate a naturalistic one.
I suspect that the answer is related to the fact that brachiating, herbivorous, arboreal apes with grasping hands and binocular vision left the forest for the savanna, stood upright freeing their hands for tool making and spear throwing if they could evolve the intelligence to exploit this potential, became omnivores, formed bands for cooperative hunting making the ability to communicate and strategize more important (made them better adapted) if they could develop the neural circuitry necessary to support those activities.
Perhaps these changes in the brain leading to intellect and abstract thought may have to occur in an animal that already has the necessary physical attributes in place for the cost of a bigger brain to be justified by the benefits. Maybe you need the skills and attributes of a jungle ape modified by those beneficial to a plains hunter for big brains to become profitable. We pay a high price for them in terms of the brain's oxygen and glucose consumption - about 20% of the body's total - and relatively premature births compared with other apes due to the infant's relatively large skull for developmental stage, so these big brains might not be worth it in just any animal body.
