A recent study showed that there are several animal species that may be as a human being. Dolphins are considered some of the smartest animals on Earth, with the ratio of their brain size relative to their average body size being second only to humans. Octopuses have the largest brains of any invertebrate. Crows- These remarkable birds are capable of constructing tools, usings them and saving them for future use. Rats dream in a similar way to that of humans.