they investigate how simple machines, such as levers or ramps, must have been used by Neolithic people to move the enormous rocks at the site;
(they; investigate; how simple machines, such as levers or ramps, must have been used by Neolithic people to move the enormous rocks at the site)
they
investigate
how simple machines, such as levers or ramps, must have been used by Neolithic people to move the enormous rocks at the site