Cutting-edge science? Remarkable powers of regeneration from a mutated X gene make Wolverine a formidable fighting force. Credit: TWENTIETH CENTURY FOX

Science fact is the loose basis for the fantasy in the current spate of movies based on comic-book characters. Peter Parker was bitten by a genetically modified spider last year to become Spider-Man (in the original 1960s' comic the spider was radioactive, but that was a different age).

Director Bryan Singer's latest film, X-Men 2 (Twentieth Century Fox), is no different, ending with a flowery but accurate description of evolution by punctuated equilibrium. This second adaptation of the popular comic X-Men opened worldwide at the beginning of May.

The X-Men are a band of superheroes (Homo sapiens superior) who possess a mutated X gene, which has an extraordinarily variable phenotype, allowing some mutants to walk through walls, some to shoot ice from their fingers, and some to perform Moses-like acts of water telekinesis. (The X gene's normal function is not revealed.) The team is led by a powerful telepath, Charles Xavier (played by Patrick Stewart), a benevolent leader who promotes the integration of the mutants into an otherwise hateful society.

Xavier's gang faces two arch-rivals: a human bent on wiping out all of the mutants, and a concentration-camp survivor, Magneto (Ian McKellen), who can control magnetic fields to the point of being able to extract iron from blood. Magneto fervently believes that mutants are the natural inheritors of the Earth and that mankind should voluntarily go extinct to bring this about.

Themes of biological determinism are touched on in this fun, but perhaps overlong, film. Magneto encourages a young mutant to join him, telling him that his genetic abilities render him “a god amongst insects”. The wise Xavier offers a counterpoint later: when his team question why one of their number commits an act of self-sacrifice, he weightily declares that the protagonist, against her nature, “made a choice”.