["and I read he offered to dedicate Capital Vol. I to Darwin, who declined not wanting to offend his religious relatives."
You read wrong:
http://www.gruts.com/darwin/articles/2000/marx/index.htm]
I checked out the link. I'm not real comfortable with a template-built website named "www.gruts.com" as an authoritative source of information, it also has no outside links to the sources in its explanations, only one link the the Origin of Species.
It does have all the names and dates of the sources, though. I don't have time to hunt them down now, the site appears on the up and up, so I'll accept the explanation, but I have it on my to do list to verify all the source info.