Considering the mummies in question all came from the same collection, and that other mummies from roughly the same time period have no such residue, it seems the most likely explanation is contamination of some sort. This would also fit with the fact that the results haven't been able to be replicated.

That said, there are some plants in the area with a certain degree of nicotine in them. Eggplant, for instance, if eaten in a high enough quantity could give some of the results the archaeologists reported.

I would like to add a little to /u/Quouar's comments here - I agree with the contamination idea, it's much more reasonable and substantive than pan-Atlantic contact. However, not only do we not have evidence of real contact across the Atlantic between South/Mesoamerican groups and African groups, we have very scant evidence that Mesoamerica and South America were in contact with each other! In terms of Pacific trade we know corn made its way down the coast, perhaps ceramics went a little ways up the coast, but we don't see coca use in Mexico, and we don't see chocolate in the Andes. These are some serious luxury goods - and perhaps they were shuffled around more - but we simply don't have the archaeological evidence to back it up.

Now, folks like Thor Heyerdahl, they don't let silly things like "no evidence" stop them from concocting fanciful hypotheses of what could have happened...

EDIT: Sorry, should have said "we simply don't have much archaeological evidence to back it up." As /u/snickeringshadow notes, there are some really interesting interactions potentially going on 1300 years ago - but that is a far cry from ancient Egyptian contact with...what, Initial Period cultures on the west coast of Peru? Early Olmecs in the Yucatan?

You may want to ask r/ancientegypt this question as well

Cacao or coca plant?

Archaeologists have been fooled so many times over the years by either mistakes or deliberate hoaxes that claimed dozens of different groups had come to the New World.

Essentially it's now become a topic where academics would want photo evidence from your time traveling camera of Acamapichtli and Amenhotep III smoking a cuban cigar together, before they're willing to talk.

On a side note, if there was significant evidence indicating coca and tobacco use in Egypt, why didn't any of these plants accompany them back to the Old World for cultivation?

I have a related question. Have any of you guys seen this BBC documentary, and does it hold water?
http://www.youtube.com/watch?v=r6IrMjfbh6E

TLDR; Black aborigines were the first to colonize the Americas but were mostly wiped out by the Amerinds. One tribe living in Tierra del Fuego survived into modern times but most eventually died by disease. Two sisters, believed to the be the last people left from this tribe, were found and genetically tested. Showed they were at least part Black Aboriginal.

Edit: So I had seen this years ago in school and thought they genetically tested the sisters. But so far all I can find is references to 'skull shapes with aboriginal characteristics'. I'm just going to watch the whole thing to see if there is more to it. Edit 2: Watched the whole thing and no mention of genetics. I did find this article which sites several papers and some mention Fuegion and patagonian genetic differences, though the site it came from has since been redirected to a random chinese site. http://www.semiaquatic-ancestors.nl/darwin_bronnen/fuegans_herkomst_feiten_dna/text-FuegianGenetics.htm Edit 3: More searching found the archive of the site here http://web.archive.org/web/20130602035534/http://andaman.org/
BUT I also found a interview with "George Weber" the creator of the site, and it describes him as a "Swiss businessman and independent scholar."
Going to have to rate this as mostly rubbish then.

• All of the mummies in the collection have around the same level of Cocoa despite being sourced from different sites, strongly suggesting contamination happened at the collection. NOTE the cocoa was NOT found in the tombs, it was found in mummies taken from tombs a long time after the time these mummies were found, after they had been stored and handled.

• Whether it was even really found is a moot point, the collectors haven't allowed the results to be verified through a second outside analysis, we only have their word for it.

• The nicotine also found doesn't need to be from tobacco, plants known to the Egyptians such as belladona also contains it.