Nothing Marx ever wrote makes any reference to Darwin or his work. Nothing. Marx was already an active socialist agitator and author before Darwin published anything about evolution. There is no connection at all between communism and the theory of evolution. In fact, "from each according to his needs" is a flat-out contradiction of how natural selection operates. The claim that Marx built his whacko theories on Darwin's work makes no sense at all. It's a bizarre fantasy.
And yet Marx says this of Origen of Species,
"Although it is developed in the crude English style, this is a book which contains the basis of natural history for our views."
Marx here actually calls evolution the basis of his views which devloped of course into communism.
Does Darwinism align better with Communism (Socialism, Humanism, Big Governmentism to lead the less evolved...) or Christianity (Freedom based on principled responsibility enabling free-markets, self-protection, land ownership...)