Moonbat analysis--I doubt the Wash Post called the Mongols "a species". I am certain that this is yet a way to blame someone else for the pitiful state of Islamic nations today. Eastern Europe was overrun by the Mongols--they made it to the gates of Vienna and they still made it into the 21st century, didn't they?
Still, the Mongols brought about the destruction of Arab rule in the Middle East.
Mooselimbs will always blame someone else -- they forget that the Islamik 'culture' was really just an amalgamation of Greek, Persian, Egyptian and Indian cultures -- the conquered peoples. Around the time of the Mongol invasions, these were being completely forced to convert. After that happened, the civilisations decayed.
I think the species argument relates to the fact that Genghis's genes have been passed on through many descendants across many different cultures. Too put it bluntly, he raped/copulated with a phenomenal amount of women wherever he conquered.
No other individual comes close to Genghis Khan in terms of their contribution to the human gene pool. A species, perhaps not, but a notable (and probably pleasurable) accomplishment from an extremely talented marauder.
The Muslims were defeated at the gates of Vienna. The Mongols breached Europe at the battles of Liegnitz and Mohi (a lot earlier), with the Mongols withdrawing to deal with succession at the death of the khan (on of Ghengis' sons, Ogedai I believe).