THESE MAMMAL ANCESTORS BIRTHED LIVE YOUNG FAR EARLIER THAN THOUGHT

Scientists have uncovered evidence that at least one mammal ancestor reproduced by giving birth to live young, rather than laying eggs. According to a recent Science News report, growth rings on a fossil bone dated to 236 million years ago indicate viviparity in a group of early mammals. This finding pushes back the emergence of live birth in mammals by roughly 200 million years.

The fossil bone, found in a rock layer that dates to the late Triassic period, contains distinct growth rings that researchers interpret as markers of embryonic development in utero. While the study does not identify a specific species, the presence of these rings suggests that some early mammals had evolved viviparous reproduction before the diversification of modern placental mammals. The research was published by the Science News editorial team and does not include direct quotes from the authors.

This discovery challenges long‑standing assumptions that early mammalian ancestors reproduced by laying eggs, a trait seen in modern monotremes. It underscores how paleontological data continue to reshape our understanding of mammalian evolutionary history.

• Growth rings on a 236‑million‑year‑old fossil bone suggest viviparity in an early mammal ancestor
• The evidence indicates live birth emerged much earlier than previously thought
• The finding revises the timeline of mammalian reproductive evolution

Read the original source for full detail available at Science News src