What are some of the major themes in "The Children of Men" by Alfonso Cuaron?i need to form a thesis statement based on a major theme in the film

The book is by author P.D. James. 

Set in England during 2021, it is about a world in which women cannot conceive, and babies have not been born since 1995. Xan Lippatt, Warden of England, is the dictator of a country afflicted by a pervasive negativism and malaise, with people finding solace with dolls and kittens, which they treat like their own newborn and even baptize, one of the few remaining religious rites.

The second half of the novel is a compelling narrative of the rebels in flight, motivated primarily by the discovery that Julian, one of their two women members, is pregnant. The child’s father is not her husband Rolf, but Luke, another renegade and a former Anglican priest.

Notwithstanding their foolhardiness, pettiness, selfishness, and disunity, the rebels represent the indomitability and indestructibility of the human spirit against all odds. While P. D. James indicates through Theo that the decadence of the 1990’s led to the universal infertility, she also suggests that if faith and love prevail, deliverance may come. The Christian symbolism in THE CHILDREN OF MEN is unmistakable.