', 'POPUP30960');
//]]></script><span class="glosstext" id="POPUP30960" style="display: none;"> An unrooted tree is one in which no assumption is made regarding the ancestor of all the taxa in the tree.</span> because it does not require the assumption of a constant rate of evolution.   Finding the root requires an outgroup taxon.  In the absence of outgroup <a href="javascript:TextPopup(this)" id="HotSpot40025" class="glossterm">taxa</a><script type="text/javascript">//<![CDATA[
TextPopupInit('HotSpot40