public function deleteAncestors($sosa) {
        if(!$this->is_setup) return;
        $gen = Functions::getGeneration($sosa);
        Database::prepare(
            'DELETE FROM `##maj_sosa`'.
            ' WHERE majs_gedcom_id=:tree_id and majs_user_id = :user_id' .
            ' AND majs_gen >= :gen' .
            ' AND FLOOR(majs_sosa / (POW(2, (majs_gen - :gen)))) = :sosa'
        )->execute(array(
            'tree_id' => $this->tree->getTreeId(), 
            'user_id' => $this->user->getUserId(),
            'gen' => $gen,
            'sosa' => $sosa
        ));
    }