This isn&#x27;t true for all species, it&#x27;s (in a way) different depending on species.  Your statement assumes that evolution is a constant, time-dependent process; it isn&#x27;t.<p>For an example, I point to the horseshoe crab.  We&#x27;re separated by x million years of evolution from the horseshoe crab, because at some point there&#x27;s a common ancestor.  Its ancestor evolved to the horseshoe crab, millions of years ago, and then <i>stopped</i>.  Meanwhile, our ancestor continued to evolve into us.  The horseshoe crab is a prehistoric animal, a &quot;living fossil&quot;.  It hasn&#x27;t evolved significantly in millions of years.  This is quite different from mice.<p>Another example is the coelacanth fish; it was thought to be long-extinct as we have prehistoric fossils of it dating to the dinosaur days.  Turns out it&#x27;s still alive.  Another less-extreme example is the shark: it&#x27;s a little different than its prehistoric ancestors, but not much.  I&#x27;m sure a biologist could point to a bunch of other species that haven&#x27;t changed significantly since the days of the dinosaurs.<p>Mammals like mice have indeed been evolving just as long as we have, but many non-mammalian species have not.