Remember the picture above? I used it in a post from last week about a team of scientists who had reconstructed the last ancestor of all placental mammals—that’s every human, monkey, bat, dolphin, lion, pangolin, shrew, antelope, and sloth.

The animal ended up looking like a furry-tailed shrew, which came as a surprise to absolutely no one. But far, far more went into this portrait than just “Paint something small, scurrying, and a bit like a shrew.”

To reconstruct their ancestral creature, the team studied 80 placentals, both living and extinct, and painstakingly analysing each one according to around 4,500 different anatomical traits. All of these details went into the reconstruction. Then, as with many palaeontology papers, the team turned to