The mammalian olfactory system is capable of detecting thousands of different odor molecules. The olfactory
receptor-gene superfamily is the largest in the mamalian genome. More than 1000 genes are scattered throughout
the genome. The dog, manīs best friend, relies on his nose and is best served by those many genes. However,
the putative benefit of this genetic load for humans is not that clear and will not be discussed here.
Anyway for primates and humans the face is the best discriminator. According to the often cited expression by Theodosius Grigorevich Dobzhansky (Феобосий Гриэорбеецч ДоБржанский, 1900-1975) "Nothing in biology makes sense except in the light of evolution" one could argue that for monkeys in the savannah and for stone age human hunter-gatherers face recognition of friends or enemies in a distance and independent of the direction of the wind was certainly an advantage. There is now ample evidence that face recognition differs in some way from other object recognition.