A 236-million-year-old fossil could rewrite the story of mammalian birth

Scientists may have uncovered evidence that a mammal ancestor was giving birth to live young 236 million years ago. A fossilized cynodont showed a neonatal growth line and an unusually large birth size that closely match patterns seen in modern mammals. The discovery could push the evolution of live birth back by up to 95 million years. It also raises the possibility that many supposedly “modern” mammalian traits evolved surprisingly early.