Scientists have pinpointed how sperm and egg join to spark new life across the animal kingdom, from fish to people. New research by scientists in Austria shows that fertilization works like a lock and key. The study was published Thursday in the journal Cell. Andrea Pauli and her team at the Research Institute of Molecular Pathology n Vienna found that three proteins on the sperm join to form a sort of key that unlocks the egg, allowing it to attach. Their findings show how this process has persisted over millions of years of evolution.