BISHOP, Calif. — Before the Egyptians built the Pyramids, before Jesus was born, before the Roman Empire formed or collapsed, the trees were here.  Ten thousand feet up in the White Mountains of central California, in a harsh alpine desert where little else survives, groves of gnarled, majestic Great Basin bristlecone pines endure, some for nearly 5,000 years. … These ancient organisms, generally considered the oldest trees on Earth, seem to have escaped the stringent laws of nature.  …“Bristlecones are kind of magical that way,” said Constance Millar, an ecologist who for more than three decades has been studying the pines, which grow only in California, Nevada and Utah. Wandering the Ancient Bristlecone Pine Forest in Inyo County, where these conifers have eked out an existence for millenniums, she said, “gives you that sense of infinity.”