Researchers report that early mammals did not necessarily live only as solitary animals. They describe an evolutionary timeline in which small, egg-laying mammal ancestors that appeared about 200 million years ago develop the ability to feed their young using milk from specialized glands.
By around 160 million years ago, the first mammals with true placentas emerge. These mammals give birth to live young that are connected directly to the mother through the placenta during pregnancy. The placenta enables the exchange of oxygen and nutrients to the developing offspring, while also carrying away waste products.
The outlets frame the new interpretation around animal social behavior: rather than assuming all early mammals were loners, the account suggests some may have lived in pairs during the same broader period when dinosaurs were present. Phys.org and AllAfrica both summarize the evolutionary background for milk and placental development and present the idea that early mammals could show social pairing, though the available summaries focus more on evolutionary traits than on specific behavioral evidence.
