Necks for sex? No thank you, we're sauropod dinosaurs
If asked "Why do giraffes have such long necks?", the majority of people - professional biologists among them - will answer that it's something to do with increasing vertical reach and hence feeding range. But while the 'increased vertical reach' or 'increased feeding envelope' hypothesis has always been the most popular explanation invoked to explain the giraffe's neck, it isn't the only one.
Source: scienceblogs.com