"Look in the mirror, and don't be tempted to equate transient domination with either intrinsic superiority or prospects for extended survival"

This quote by Stephen Jay Gould is a tip to not be deceived by looks. It is informing us to look in the mirror and not be lured to think that due to the fact that something is popular or effective in the present minute, it is always better or will last forever. This is a warning versus thinking that something is superior or will last just because it is presently dominating. Gould is cautioning us to not be fooled by the transient nature of success and to not relate it with intrinsic supremacy or long-lasting prospects. He is advising us that what is popular now might not be popular in the future which we ought to not be fooled by the illusion of permanence.