Alfred was a son of Æthelwulf, king of Wessex, and his wife Osburh. According to his biographer, Asser, writing in 893, "In the year of our Lord's Incarnation 849 Alfred, King of the Anglo-Saxons", was born at the royal estate called Wantage, in the district known as Berkshire (which is so called from Berroc Wood, where the box tree grows very abundantly)." This date has been accepted by the editors of Asser's biography, Simon Keynes and Michael Lapidge, and by other historians such as David Dumville and Richard Huscroft. However, West Saxon genealogical lists state that Alfred was 23 when he became king in April 871, implying that he was born between April 847 and April 848. This dating is adopted in the biography of Alfred by Alfred Smyth, who regards Asser's biography as fraudulent, an allegation which is rejected by other historians. Richard Abels in his biography discusses both sources but does not decide between them and dates Alfred's birth as 847/849, while Patrick Wormald in his "Oxford Dictionary of National Biography" article dates it 848/849. Berkshire had been historically disputed between Wessex and Mercia, and as late as 844, a charter showed that it was part of Mercia, but Alfred's birth in the county is evidence that, by the late 840s, control had passed to Wessex.