That ancestor is called LUCA, the last universal common ancestor, and there is no fossil record to tell us what it looked like. Luckily, we have Jonathan Lambert.

An evolutionary chart of different human ancestors. “Seeing Lucy’s face is like glimpsing a bridge to the distant past, offering a visual connection to human evolution,” said Moraes.

The ancestor would later evolve into all placental mammals. These are the mammals that keep their fetus alive with a placenta, as opposed to those who develop their young in pouches or in eggs.