ABSTRACT. Ayala reviews our knowledge of human evolution and points out that we are "unique" in a fundamental way; most notably we have "culture," a distinctive form of heredity that supports cultural evolution, a mode of adaptation to the environment much more effective than the biological mode. Whether there may be intelligent beings elsewhere in the universe must be responded to with an unequivocal "no." The improbabilities involved surpass by many orders of magnitude the probable number of planets suitable for life in the Universe.