cats

<?php  if( is_category() ) : //because this makes only sense in a category archive page
$cats = array();
$cat = get_query_var('cat');
do {
$cats[] = (int)$cat;
$cat = get_category($cat)->category_parent;
}
while($cat);

$args = array(
'category__and' => $cats,
'orderby' => 'post_date'
);
$posts = get_posts( $args ); ?>
<ul>
 <?php   foreach($posts as $post) {
   ?>
     <li><a href="<?php the_permalink() ?>" title="<?php the_title_attribute(); ?>"><?php the_title('')?></a></li>
   <?php } wp_reset_postdata(); ?>
</ul>
<?php endif; //ends: if( is_category() ) ?>