Through Gertrude Caton-Thompson
Mary met Louis Leakey, who was in need of an illustrator for his book, Adam's Ancestors. While she was doing that work they became romantically attached. They shared common interests and values: a love of freedom and dislike for rules, an egalitarian frame of mind extending even to animals, a desire for adventure, and a passion for archaeology. Louis was still married when he started living with Mary, which caused a scandal that ruined his career at Cambridge University. They were married when Louis' wife Frida divorced him in 1936.
From then until about 1962 Louis and Mary faced trying circumstances together. Early in their relationship he nursed her through double pneumonia. They had three sons: Jonathan in 1940, Richard in 1944, and Philip in 1949. The boys received much of their early childhood care at various anthropological sites. Whenever possible the Leakeys excavated and explored as a family. The boys grew up with the same love of freedom their parents had.
Louis was not always faithful to Mary, as he had not been to his first wife Frida.After Louis became known as a womanizer the intimate side of the marriage was effectively over. Meanwhile, Mary's life consisted mainly of her children, her dogs, and her archaeology.
After the death of her husband, she became a leading palaeoanthropologist, helping to establish the Leakey tradition by training her son, Richard, in the field.