That a long time ago they had very short necks. The giraffes that had very short necks couldnt reach the leaves off the trees, so the ones with shorts necks soon died out because the longer necked giraffes were eating all of the leaves. Gradually longer necked giraffes were mating with other longed necked giraffes, then thier babies also had long necks. This shows how giraffes adapted to the environment they live in.