The pyramids in and around Giza have presented a fascinating puzzle for millennia. 

How did ancient Egyptians move limestone blocks, some weighing more than a ton, without using wheels? Why were these burial structures seemingly built in the remote and inhospitable desert? 

New research — published Thursday in the journal Communications Earth & Environment — offers a possible answer, providing new evidence that an extinct branch of the Nile River once weaved through the landscape in a…