we're just rainbows dreaming we're human

Not a biologist, but the evolution of mammals is way more granular than you might expect. Humans are the sole surviving species of the genus Homo, which was a real party before the other ones went extinct. You're in for a fun time.

Domestic cats are believed to be domesticated not from tigers, but from the African wildcat:

Which evolved to be small just because it's sometimes more useful to be small.

And no, hamsters are not off-brand rats. They're part of the rodent order, which includes beavers, moles, capybaras, guinea pigs (yes, also wild) and lots of other fun things:

All California sheephead start life as female and move through an array of colors and body shapes as they mature. Some female adults may transition to male as social and environmental factors shift, balancing the delicate ratio of individuals in their population.

While male California sheephead are largest and easiest to identify at a glance, a closer look at the lively waters of our Kelp Forest exhibit reveals a variety of female sheephead swimming through these fascinating life stages.