Confirmed: Hard rock and heavy metal lead to sex

When Nuna formed, large bodies of magma were injected into the continental crust where they cooled to form granite. This igneous rock is rich in metals including zinc, molybdenum and copper. Over time, natural erosion brought the granite to the surface where it, too, eroded, releasing the metals into the soil and water. Sedimentary records show that they were present in near-surface reservoirs and shallow bodies of water by 1 to 1.5 billion years ago, says Parnell.

“These metals were used by early cells to develop enzymes that enabled them to carry out a greater diversity of functions and begin to sexually reproduce,” says Parnell. “They gave early life the added dimension of natural selection and variability.”