It is possible that the incest taboo arose this way, I suppose, and certainly it seems likely that it is intertwined with the Westermark effect in some way, but they are still not the same thing. They sometimes apply to different people: e.g., the Westermark effect will not apply to siblings raised apart, but the incest taboo still does; the Westermark effect, but not the incest taboo, applies to unrelated kibbutzim raised together.
Also, my impression is that the Westermark effect does not make the relevant relations seem disgusting so much as just uninteresting, whereas violations of incest taboo typically do evoke reactions of disgust (from third parties - presumably at least one of a pair violating the incest taboo will actually be enjoying it).
I haven’t seen any evidence, just unsupported assertions, bad math, and fuzzy, “of course we’re all related,” thinking. MRCA for an entire continent in four generations? That’s ridiculous on its face!
Is there any proof that the exogamists are more fertile than average? If not, perhaps the one scion who married out this century, of a given endogamous tribe, left no fertile grandchildren. Oops.
Shall we assume that no tribe practices forced endogamy? Ooh, let’s! We can go on to assume that no one eats pork or wears eye makeup, while we’re at it!
But it didn’t. You have no evidence that it did. You’re just asserting that it must have.
Hawai’ians less isolated from [other] Polynesians than Europeans from what? Not other Europeans.
That said, yes, it’s fair to say that the OP is at most a 10th cousin (if I were betting in a pool, let’s say 8th or less) of his girlfriend, unless their heritages are from other sides of the planet or something.
His point is valid, even though the example given may not work exactly. The simplest example of it that I can devise involves 15 people:
Generation 1:
Alan and Barb have two kids - Geoff and Heather
Carol and Doug have two kids - Ian and Jane
Emma and Fred have two kids - Karen and Luke
Generation 2:
Heather and Luke have a kid - Mark
Geoff and Jane have a kid - Nick
Ian and Karen have a kid - Olivia
Now Generations 1 and 2 die. Everyone left (Mark, Nick and Olivia) is a first cousin to any other person, even though the MRCA is more than 2 generations back - in fact, an arbitrary number of generations greater than two back, since we know nothing about the genetic separation between the people in gen1.
Obviously the modelling of this over the entire population of the world is incredibly complex, but I would pick 30 or less as the most likely number that constitutes a factual answer to the OP’s question. 30 generations back gives you a number of ancestors (1 billion) which is roughly double the world population at the time (about half a billion or less in the 15th century) - I would call that more than enough to ensure that at least one of those ancestors was shared between every two people on earth, even if it’s not the same ancestor for every pair.
As I explained in my previous post, MRCA is irrelevant. FWIW, the MRCA appears to go back about 250,000 years, maybe 10,000 generations.
Incidentally, I was wrong in my previous post (#28) in stating that Alice, Bob, and Charles, although first cousins to each other, shared no ancestor later than the third generation preceding. Actually, their MRCA could be indefinitely far back in the scenario I envisaged.
Incidentally, the question of whether second cousins thrice removed could be of marriageable ages is not clear. I was thinking about my mother’s first cousin cohort that ranged over 44 years, from her older brother born in 1904 to her first cousin born in 1948, the same year as my sister. Now if you go to second cousins, the age distribution could get very large and, anyway, a 60 or 70 year old man can still father a child.
[QUOTE=Derleth;15521647
The medieval Catholic Church defined beavers to be fish, which, in this thread, sounds awesomely sexual but in reality was just about satisfying the urges of a bunch of cloistered monks.[/QUOTE]
This is true only if by “medieval” you mean the 17th century, and by “cloistered monks” you mean Quebecois.
Several examples have been posted. Here’s one from Real Life!
My present neighbors include two brothers from another province who came here and married unrelated women. One of the wives has a brother married to the other wife’s sister. All three of these couples had children. (In fact, I’ve been to weddings for four of the children from these marriages.) All of these children are either siblings or first cousins with each other, yet share no known common ancestor. (Those connections don’t involve us, but my wife has relatives who are cousins both on her mother’s side and on her father’s side. And, no, none of this involve inbreeding – in all this genealogy I can’t think of a single instance of known relatives marrying.)
To answer OP’s question (but with the numbers 12th, 20th, 30th, just wild, probably conservative, estimates):
I guess that a typical American is 12th cousins (or closer) with most other typical Americans.
That same American is 20th cousins with 99% of living humans, and 30th cousins with 99.99%.
Getting that 99.99% up to 100% may be fraught with uncertainty, due to outliers like the Sentinelese.
It’s not very interesting or enlightening to dismiss this concept based on two people on earth who may 51st cousins instead of 50th. The measure of this is the closeness of relation between the vast majority of people on earth. Is it around 50 or not? If there are some outliers that would be interesting in of itself, but even getting to the point of saying it’s more likely than not that you are no more than a 50th cousin of everyone on earth is something of note.
I’m also getting the impression reading this that a small isolated group doesn’t change things much. Members of that group will all be closely related, and any one of those members who are related to someone outside of the group will bring the whole group in close relationship with the rest of the world.
My grand mother married my grand father(no duh!). Somewhere around the same time, her sister married my grandfathers brother(neither set are twins). So my dad has, in effect, a bunch of double first cousins. This is an example of ancestor collapse without any cousin kissing.
Double familial weddings like that were probably not uncommon in the past.
What is interesting is that both marriages produced large families, twelve kids each. They grew up feeling a special bond.
The problem is complex with european exploration, but the real question - difficult to answer - is how often people went far afield to reproduce. The math for Australia works great if it is a numberline or a road, but in a 2-dimesional map that process can take a while. Then there’s the hard-to-navigate geographical barriers, like Tasmania, Tierra del Fuego, the gap between Panama and Columbia, Newfoundland, etc. These barriers are a lot easier for the original inhabitants to cross, there were no hostile locals defending their territory on the other side.
If a common ancestry has to do an end run around a desert or mountain range, it will take a lot longer than going straight across.
In a tribal village of say, 50 individuals, aboriginal, Indian, what have you - how long before everyone, or even half the population, are related to the stranger who came into their group many moons ago? Lets’ say it’s distributed 10-20-20. That is, 10 of the oldest generation, 20 of aprents, 20 of children. Running Mouth joins the tribe, or Happy Hips gets knocked up in the bush. A generation later, there’s 2 children. they marry, 2 generations later there’s 4 related offspring, So 3 or 4 generations later everyone can claim ancestry, provided not too many newbies join the group or not too many women are traded to the next tribe. Double the social group and the “leavening” takes longer, the only saving grace may be that more strangers are coming in.
I don’t follow you. There will always be common ancestors. The only question is how far we have to go back to find the most recent common ancestor.
New Guinea has a challenging terrain that led to extreme isolation. The Dani people of the Grand Valley in west New Guinea believed that they were the only people in the world until they were discovered from the air in 1938. The interior of east New Guinea similarly was thought to be empty until prospectors discovered it was populated in 1930.
Yes, of course the ancestors of the uncontacted tribes of South America were integrated members of the pre-Columbian civilizations. After those civilizations collapsed, however, they retreated into the rain forests and avoided contact with Europeans. It seems likely that at least some of them have no European ancestry (though most, of course, do).
I don’t mean that the Hawaiians are autochthonous, with no relationship to other humans in the world. Rather, I mean that there are Hawaiians all of whose ancestors are Hawaiian, to a point prior to the discovery of Hawaii by Captain Cook. There are several thousand purebred Hawaiians, and records are quite good for most of the intervening period. Of course, if you go back far enough then the Hawaiians came from elsewhere in Polynesia, and there also has been at least some contact historically between Hawaiians and other Polynesians.
My point in all this is not to preclude the possibility of contacts, but to argue that, for at least some people, it would have taken a long time to establish descent from the MRCA. For example, suppose that I am right that there are native Americans in South America with no post-Columbian European or African ancestors. How then would there be descent? Well, the Bering Strait is a somewhat porous barrier, so we don’t have to go back to the original settlement of the Americas. But it takes time for a person at the Bering Strait to have a descendant in South America.
What bothers me about the way Blake is framing things is that he seems to think that if present-day Eurasia has a MRCA, say, 3000 years ago (which is not necessarily the case, btw) and there was any intermingling between Eurasians and other populations in the last 3000 years, then of course everyone has that same MRCA. And it doesn’t work that way. Intermingling of non-Sentinelese with Sentinelese (substitute Amerind, New Guinean, Khoi, whatever) could have happened in the last several centuries, but before the intermarriage that creates an “Eurasian MRCA 3000 years ago.”
And of course there’s not an inevitable, consistent rate of intermarriage or pedigree collapse. So despite what some people think, even a Eurasian MRCA is thousands not hundreds of years ago.
What you seem to be missing is the fact that none of these remote tribes needed to have contact with Europeans in order for them to ALL have European ancestry.
How to explain this paradox?
This is because they didn’t need to ever come in contact with a European. All that is necessary is for someone in the village to intermarry with someone from the next tribe over, who themselves is the descendent of an intermarriage between a Native American and a European. Feel free to add as many intermediate steps in the middle as you like.
In addition, with the small size of the typical tribe, it does not take long before everyone in the village ends up with European ancestry as well.
I don’t understand what you’re nitpicking. We said most recent common ancestor. So if Y-Adam has a daughter and several sons, that daughter would replace her grandmother as the most recent ancestor of everyone. And if that daughter bore all of humanity to more than one of Y-Adam’s sons, then he can’t ever be stripped of his “Y-Adam” title, presuming no more bottlenecks happen (an apocalyptic flood, perhaps).
Now either presume that the line is more complicated or even that Y-Adam never met his daughter. Then we’d have the case, as I said, that MRCA-male never knew MRCA-female. Sure, Y-Adam knew his mom, but that doesn’t mean she’s the most recent.
No, I just screwed up my example. I thought of the correct version in the shower and was loth to bring my laptop in there with me, but Aspidistra got to it before me:
Yeah, that. Essentially, 3 couples live in houses in a cul-de-sac. They each have a boy and a girl and superfluous children we don’t care about. The eldest son marries the eldest daughter of the house to the right of his (and therefore the daughters marry left). They all have kids. Those kids, no matter how many there are, are all first cousins or siblings. Yet no single ancestor can be pointed to as having sired/borne everyone.
Extended, unproven theory: With X couples, you need X generations (inclusively) to create the same phenomenon. So with 4 couples, everyone can find a common great-grandparent.
Well, Blake is reflecting the results of the peer reviewed scientific journals on the subject. If you have better data, perhaps you should publish an article and debunk that data.
The most recent common ancestor was far more recent than either Y-Adam or Mitochondrial Eve. And if we’re going to specify “most recent common male ancestor” and “most recent common female ancestor”, the odds are overwhelming that the two of them were either married, or a parent-child pair.
Think of it this way: There’s a most recent common ancestor. That person is either male or female; let’s say without loss of generality that he was male. Well, if he was monogamous, then his wife is also a most recent common ancestor. And even if he wasn’t monogamous, then his mother would also be a common ancestor, and therefore the most recent common female ancestor can’t possibly be any earlier than one generation before him. So for the most recent common female ancestor to be anyone other than the mother of the most recent common male ancestor, you’d need to find a different rout of ancestry to someone else, within a single generation of the route you found to the first guy.
This looks like a misunderstanding of the concept of “Y-Adam”. At the time Y-Adam lived (whenever that was), there were lots of other people around, both male and female. So he didn’t necessarily have a daughter, and if he did she did not have to mate with her brothers, nor did she become an ancestor of all of humanity.
In fact, the names “Y-Adam” and “mitochondrial Eve” are probably more confusing than they are worth, because of course they make people think of the Biblical Adam and Eve.
No. That is not how reasoning works. Blake has to provide the reasoning why foolsguinea’s argument is invalid, seeing as an obvious example of the logic being flawed was given. Magazines reference peer researched journals all the time and get things horribly wrong. It’s not some magic wand that makes you correct.
And if you want to claim that there are peer reviewed journals that agree with you, then it’s on you to provide the citations. Your claim is essentially meaningless.