Several things, but consider one: the contention that evolution may tend towards consciousness. Nagel is explicit that he himself is not countenancing a designer. Rather, he wonders whether science needs to entertain the possibility that a teleological trend is immanent in nature.
There it is. The t-word – a major taboo among evolutionary biologists. Goal-directed explanations automatically question your loyalty to Darwin. As Friedrich Engels celebrated, when reading On The Origin of Species in 1859: "There was one aspect of teleology that had yet to be demolished, and that has now been done." But has it? This is the moot point.