Fish don’t have a big brain but it’s big enough to find a date,stay alive, and find food…
Interestingly, brain size matters less than you'd think. Lemurs with brains 1/200th the size of chimps' have a similar tested IQ.
And some intelligence seems pre-programmed, rather than the result of brain activity. Bacteria have no brains whatsoever, but will do smart things like share genes that protect against antibiotics.
They self-engineer mutations, too, contrary to neo-Darwinian random variation doctrine. Heck, they will even gather a quorum and chemically "vote" on what to do next in puzzling situations!
