No Two Alike

Absolutely. No two animals are exactly alike. Let's just think vertebrates here.
All animals share many similarities – a spine with a right side features that are reflected as if a mirror image on the left. I don't expect that matters to any vertebrate except humans.
I wanted a really spiffy scientific definition of animal and to the a dictionary I did trot. The American Heritage Dictionary defines “animal” as any mammal except humans. Is that interesting or what?
We want to blend and be like everyone else. Sometimes.
We want to be unique, independent of everyone else. And each one is. That sounds on the face of it as impossible. But animals are very complex. Not much of a switch of a protein in a Hox gene will make a big difference in skin texture, hair thickness, or other visible features. I am startled when I look upon a person so familiar that I certainly know her – or him but am assured they are strangers. Often I see such a resemblance in a husband and wife that they look like siblings. Yet neither ever noticed the similarities. Then again couples show not a single similarity – well except for the usual eyes, ears, nose, etc - that they look like different clans. I probably am the only one who notices such things.
Well I am a visual person, ruled by my left brain, I guess. I am unique, even if little kids all think I am their grandmother.
Naomi Sherer