Researchers have long believed that humans were differentiated from African apes about 5 million years ago, but a recent study has suggested that this differentiation has occurred much earlier in Europe. The hypothesis is based on the discovery of 7.2 million years ago human remains in caves in Greece and Bulgaria. Researchers from multiple countries analyzed the roots of two known samples. They used specialized X-rays, or computers Tomography scans the mandibular fossils from Greece and the upper premolar fossils from Bulgaria, and finds that their characteristics indicate that the two ancient apes-nicknamed "Greek", maybe pre-humans, that is, primitive humans. According to this text, the following is true:. ['Primitive humans differentiated from European apes.', '"Greek" ancient apes have human characteristics.', 'Researchers find only roots of European ape.', 'X-ray technology can accurately calculate the age of the ancient ape man.']