Meat thinks. What an unusual idea.
But imagine if more advanced aliens, with a different unspecified substrate, were so surprised and repelled by this discovery that they decided to give us a miss.
"Oh, there's a brain all right. It's just that the brain is made out of meat! That's what I've been trying to tell you."
"So ... what does the thinking?"
"You're not understanding, are you? You're refusing to deal with what I'm telling you. The brain does the thinking. The meat."
"Thinking meat! You're asking me to believe in thinking meat!"
It's a 1991 story now available as a video with well disguised meaty looking aliens. Thanks to arti for the links.