It is arbitrary enough as to be utterly irrelevant in modern genomics. Some people cling to it, usually doctors who haven't gotten the memo, old school taxonomi

It is arbitrary enough as to be utterly irrelevant in modern genomics. Some people cling to it, usually doctors who haven't gotten the memo, old school taxonomists who don't want to let go of their traditional systems, and of course Pioneer Fund recipients. But popgen/phylogeny researchers avoid using it because of how little information it conveys due to its being so poorly defined.