Scientists think they may have finally cracked the age-old mystery of how 31 pyramids, including the famous Great Pyramid of Giza, were constructed in Egypt more than 4,000 years ago. And no, it wasn’t with the help of extraterrestrials. A groundbreaking discovery by researchers from the University of North Carolina Wilmington reveals that these ancient marvels were likely built along a now-buried branch of the River Nile, concealed beneath desert sands and farmlands. For years, archaeologists have speculated that the ancient Egyptians used a waterway to transport massive stone blocks and othe…