They would still need a time machine, as Communism was developed long before Darwin ever published. There is of course no connection between anything that Marx or Engels actually wrote and evolution as described by Darwin.
I've already pointed out a connection which Marx himself pointed out.
The time sequences the publishing of the ideations. The ideas themselves? They sure look that they arose contemporaneously in the same idea-pool of Europoean intellectual culture of the era. Afterall, it was a stress-ful era, we'd expect new species of ideations out of it, would we not?