Yes you can make beer without hops - the hops simply add bitterness and extra flavours; without them, beer would be quite sweet and very yeasty. They were introduced to Britain around 1400, but beer-drinking was a well established pursuit before then
Prior to the introduction of hops, other things would be used to add flavours, from the innocent such as Heather to the hallucinatory such as Wormwood and Henbane. Unhopped beer used to be known as 'ale' but in modern times 'ale' means beer that has been made with yeast that ferments 'at the top' in warm temperatures as opposed to 'lager' which uses the opposite process.
Almost all beer and lager now has hops in it including Ale - but you can get 'revival' beers which are brewed with herbs instead if you really search - you can sometimes find Heather Ale in Scotland, usually marketed by also telling you the tale of the last Pict who hurled himself to his death from the Mull of Galloway rather than tell the invading Scots the secret recipe for Heather Ale...