How did Thomas Henry Huxley and Charles Darwin become close colleagues?

Thomas Henry Huxley and Charles Darwin established their close relationship following a visit Huxley made to Darwin’s Down House in 1856. This meeting laid the foundation for a lasting bond between the two men and their families, characterized by deep personal and professional ties.1

The two scientists complemented each other effectively: the reclusive Darwin required a public defender for his work, while Huxley, though initially skeptical of natural selection, recognized the value of Darwin’s nonmiraculous, naturalistic approach in his own campaign to establish an independent scientific elite.1

Their families also grew close; the Darwins served as godparents to two of the Huxleys' children, and the wives of both men shared concerns regarding the theological implications of their husbands' scientific theories. This partnership ultimately led to Huxley becoming known as "Darwin’s bulldog," as he became the primary public champion of Darwin’s Origin of Species.12