Whales
Just like The Hitchhiker's Guide to the Galaxy, The Voyage Home reveals that aquatic mammals are the smartest species on Earth. Great minds think alike.
Of course, this idea totally undermines our human-centric worldview. How, you ask? Well, the crew members of Enterprise automatically assume that the probe is trying to make contact with humanity because, duh. Being humans ourselves, we can understand that this is a natural assumption—but it's not a correct one this time. Check out how Spock frames it:
SPOCK: There are other forms of intelligence on Earth, Doctor. Only human arrogance would assume the message must be meant for man.
Hey, man, who you calling arrogant? Oh, wait…yeah, that's probably fair. Anyway…
Here's another important thing to note—humpback whales have gone extinct by the time we get to the future world in Star Trek. In this way, whales represent the negative consequences of human activity against the environment. Check out Kirk's take on this topic:
KIRK: You know, it's ironic. When man was killing these creatures, he was destroying his own future.
In other words, don't bite the hand that feeds. Or should we say "flipper"? Either way, the whales in this movie show us humans' relatively insignificant status in the cosmic order—as well as our unfortunate penchant for destruction.