Mammal ancestors laid eggs, and this 250-million-year-old fossil finally proves it

A 250-million-year-old fossil containing an ancient egg with a curled-up embryo has confirmed that mammal ancestors laid eggs, resolving a long-standing scientific debate. The discovery, made using advanced imaging technology, sheds light on how Lystrosaurus survived Earth's most catastrophic extinction event and reproduced. This finding highlights the evolutionary strategies of early mammals.