Don't be an idiot. Learn these myths, and for the love of all things holy, don't propagate them!
10. If you are of Scandinavian heritage (Denmark, Norway, Sweden), you are a "Viking."
Example post: "my gma is half Swedish and I am very adventurous; must be the Viking LOL."
Vikings were the marauders sailing from Scandinavia who invaded many parts of Europe during the years of approximately 600 AD - 1200 AD. Those of Scandinavian blood are emphatically NOT "Viking." The Vikings were the adventurous ones who left. Scandinavians are descended of the ones who stayed home.
While Scandinavians may share common origin with the Vikings dating back 1500 years, technically it's not correct to say they are descended from them. And to the extent there is a gene for adventure-seeking, violence, or the so-called, "warrior" gene, it's more probable that the ones who stayed in Scandinavia (as fishermen and barley farmers) do NOT have that gene.
Many Russians, Ukrainians, English, Scots, Calabrians, Sicilians, and Northern French have a better claim to be "directly descended from Vikings." Sorry.
9. You can determine by a test on Eurogenes or Gedmatch the precise percentages of EEF-ANE-WHG that you are.
For the uninitiated, these acronyms stand for "Early European Farmer," "Ancient North Eurasian," and "Western [European] Hunter Gatherer."
Example post: "Username: SteppeOverlord EEF: 21.345%, ANE: 19.876% WHG 58.779."
It's important to note that these hypothetical populations were reconstructed from...ONE SAMPLE EACH. Thus, when you take the Eurogenes EEF ANE WHG test, you are comparing yourself to each of three skeletons: the EEF is the LBK sample found in Stuttgart, Germany. The ANE is the Mal'ta boy found in Siberia. The WHG is the Loschbour skeleton found in Belgium. Citation.
These populations were themselves admixed, especially the Stuttgart sample. It's not accurate to use one exemplar to represent an entire group, especially ones with the huge geographical ranges of the acronym populations. It's much more accurate to say that you tested whatever percentage in common with Loschbour, Mal'ta, or Stuttgart.
Many of the genes inherited so many generations ago will be the result of identical by state, (more or less coincidence, or breeding back, in a way), than Identical By Descent. Citation. Europeans are a homogenous lot, and these tests don't therefore reveal much, if anything, and the terminology, turned to shorthand, stinks.
8. Admixture percentages are due to a historical event.
Example post: "OMG! I am English, Irish, German, and Polish. But Dodecad says I have 6% Siberian; this must prove the legend in my family that my great-grandmother was a Cherokee princess!"
"I am South Italian. But Eurogenes says I have 12% southwest Asian. Must be the Greek blood!"
People tend to overestimate historical events (i.e., those we know about due to past events being recorded in writing), but tend to underestimate non-historical events. This is a recent-ness bias that comes from a little knowledge about history, often expressed in shorthand, (i.e., South Italy was Greek).
It is however, almost always not true. In the first example above: many Europeans, especially Northern Europeans, test positive for some Siberian/ANE/even Native-American-like ancestry, but this is almost certainly the result of ancient Admixture from the first Indo-Europeans from the steppe, who had substantial Asian-like ancestry. For the second example: the people who populated Italy in prehistoric times were descended in many cases from the first farmers, who came from the southeast fringes of Europe. Such signals in modern ancestry are way more likely to indicate ancient admixture from population sources with common ancestry to historical populations.
Sorry, but the boring is almost always more true than the interesting.
7. People from places with many years of recorded history are more admixed than people with less history.
example post: "If you are of South Italian ancestry, you're probably part Roman, Greek, Scandinavian, Arab, and Jewish."
This one is so obvious it is painful to have to post. But it's the corollary of number 8 above: a little historical knowledge being dangerous.
Imagine two regions: Region 1 is fairly remote, but has had extensive writing for 2600 years, and every marauder, political shift, kingdom, invasion, battle, language spoken, and petty dukedom is recorded in glorious detail. Imagine another region, Region 2, that has had extensive writing and civilization for only about 1100 years. There are large gaps in knowledge of what happened there, because of the lack of historians.
I just described Basilicata, Italy and Hesse, Germany. Yet so many online "mytholographers" perpetuate the notions that people like Italians, Jews, and Greeks (i.e., those with 25+ centuries of intense recorded history) are more admixed than those without such extensive documentation (i.e., Germans, French, etc.)
You can't escape this, on any online forum, people speculating on exotic sources in Italian ancestry, and almost no one does this for Germans and French.
Just because we don't know who was invading another area during prehistory or the Dark Ages, does it mean it didn't happen? Just because we don't know the name of the king who pillaged a territory, does it make him any less historical? Because there is no Trojan War story for Hesse, Germany, does it mean there was no warfare, invasion, or exotic influences?
The French and Germans are so "admixed" (i.e., generic European) that 23andme cannot identify their DNA 92% of the time. Citation. Yet the poor Greeks have to tolerate in every discussion, excruciating detail and speculation about every single exotic strain in their blood.
Aside from the remotest, hard-to-get-to, isolated regions of Europe (Finns, Northwest Irish, Basques, and Sardinians), everyone has been invaded, repeatedly, and everyone is very very admixed. The paradigm, of focusing only on certain peoples for this, has to change, because it's simply not accurate.
Check back soon for the rest of the Top 10 list.