 The argument is not that they were knuckle-walkers themselves  but that it is an example of "phylogenetic 'lag'".
<fluency>  The argument is not that they were knuckle-walkers themselves  but that it is an example of "phylogenetic 'lag'".
 The argument is not that they were knuckle-walkers themselves , but that it is an example of "phylogenetic 'lag'".