I'm looking for a novel from the 50s or 60s, most probably written by a British author. In the novel, explorers find an ancient starship, and reverse engineering gives humanity the same ars.
Using the information gleaned from the ship, they track the ship's origin to a planet that has signs of an advanced but vanished civilization. As they explore, the realization comes that the aliens were humans.
The Haunted Stars by Edmond Hamilton, published in 1960?
In it, several linguists are sent by the US military to a moon base where they discover that alien artifacts, including a wrecked starship, have been found. They're supposed to figure out the alien language and translate it. It turns out to resemble ancient Sumerian, and a biologist on the project concludes the aliens seem to be humanity's ancestors.
The ship's engines and other technology is reverse engineered and used to send an expedition to the alien planet, where (quoting Wikipedia):
On Ryn they land their ship next to the slagged remains of a once-great starport and the decayed ruins of the city that had stood by it, surrounded by forest.
