Hans Jonas accuses Heidegger of "never bring[ing] his question about Being into correlation with the testimony of our physical and biological evolution." Neither the early nor later Heidegger has a "philosophy of nature," Jonas charges, because Naturphilosophie demands a new concept of matter, a monistic account of cosmogony and evolution, and the grounding of ethical responsibility for future generations in an ontological "first principle." Jonas's ontological rethinking of Darwinism allows him to overcome the nihilism that a mechanistic interpretation of evolution forces upon us: a nihilism allegedly shared by Heidegger. I imagine a Heideggerian response to Jonas, and ask whether the dream of recovering a synthesis between cosmogony and moral insight has been irrecoverably shattered by modern natural science.