How much inbreeding is in all of us?

Question

Considering I have 2 biological parents, 4 grand parents, 8 great grand parents... and so on and taking 25 years to a generation:
At 1000 years ago, if there were to be no inbreeding, I should have had 1 trillion unique ancestors. Is there a calculation as to how much inbreeding is there in all of us?

Answer 1

First of all this conundrum is extremely culturally dependant. Some nomadic pastoralist groups actually prefer cross cousins as marriage partners therefore they typically have shared grandparents or in small isolated societies like the Amish and Hutterite societies social and/or geographic isolation has made inbreeding a common practice. http://www.as.wvu.edu/~kgarbutt/QuantGen/Gen535_2_2004/Inbreeding_Humans.htm In African Bantu societies alternatively the families do a deep consultation between the family elders before they "bless" the marriage in order to confirm that there are no common relatives for many generations back as inbreeding is extremely taboo in this culture. European nations are somewhere in between these two extremes and an unintentional inbreeding could even occur between cousins because of the disjointed nature of the families within our societies, although more typically these "mistakes" would be 2nd cousins at least. This article shows a group of Spanish valleys where a search through marriage records revealed that second cousin marriage rates were 4.45% where as first cousin marriages was only 0.23%. http://muse.jhu.edu/journals/human_biology/v073/73.2fuster.html Other groups, such as royalty, may actually implement such practices to keep "bloodlines" intact, although at great detriment to their genealogical health. There are many examples of this: http://findarticles.com/p/articles/mi_qa3659/is_199806/ai_n8797360 Here is a great statistical set which shows just how severe Royal interbreeding was in Europe. There is not a single example of any of them going through 6 generations cleanly and most don't even make it through 4 generations. http://members.aol.com/eurostamm/ahnen.html Anyways, as you can see from my analysis, unless you are royalty and have had accurate records taken on your family for many generations it is difficult to determine where any one individual stands in these mucky waters, there truly is no set calculation to give you an accurate estimate. This is further compounded by the fact that each culture tackles this issue so differently, and each class of society within each culture can differentiate as well.

I was happy to see that you had done your math correctly, indeed 1000 years of clean interbreeding represents 1.09951E+12 unique relatives. As this is clearly not possible due to the population of the earth being much smaller back then it is obviously acceptable to "interbreed" after some number of generations of seperation. from some of my links it seems to steadily increase in occurance amongst apparent "strangers" from the 4th generation (same great grandparents) as seen in the spanish valleys study, although I can also tell you from my own observations of Bantus in Africa, that amongst these tribes the family screening easily goes back at least 7 generations (possibly same great great great great grandparents or 128 unique relatives) with relative certainty based on naming practices, geographical areas and their oral traditions. So all our parents are definitely guilty of interbreeding probably within as little as 15 generations (32768 unique relatives) of seperation, although very likely it could even be less. If you don't want to commit the same mistake as your parents cynic, I would suggest that you marry and procreate outside your ethnic group. At least then you can guarantee that you yourself will not be interbreeding since the time of seperation between yours and your wifes respective ethnicities, despite the mistakes of your parents and your grandparents and your great grandparents, etc, etc.

Anyways, obviously after a few generations this becomes a neccesity, so weather a nomadic 3 generation seperation is accepted, a European 5 generation via mistake, or a Bantu 7 generations minimum of non interbreeding through thorough screening, eventually, something has got to give! There is no calculation, however, just extensive research of marriage certificates as this is obviously a phenomena calculated on the individual level, and not a general rule!

Answer 2

Why would inbreeding depression take us out? We aren't that closely related now. To take an example from inbred cats: they don't all get taken out in one foul swoop; neither does every single cat within the colony necessarily breed only with its sibling. As the colony multiplies, so does the possibility of mating with more distant relatives. As for the idea of an Adam and Eve as common ancestors, I don't know why that would be such a strange idea to consider, since the Discovery Channel considered pretty much the same thing in 2002, when it aired "The Real Eve," in which it was claimed that humankind shares a common genetic link that can be traced to one woman who lived in Africa more than 150,000 years ago. Obviously scientists were looking into the possibility. And if we all evolved, we must have had something similar to an Adam and Eve going on at the very beginning, since it would be highly unlikely that lots of male humans and lots of female humans just happened to evolve totally separately from one another in order to produce non-inbred offspring. Personally, I don't think evolution has done that great a job for the millions or more years it's supposed to have had to work on us. We still get diseases and weaknesses, as if we were inbred, and even though the species still survives, individually we're all "taken out" in the end, so it's going to be no use to me 500 years from now.

Answer 3

You're looking at this too close.... Inbreeding refers to coupling between close family members. Parents and offspring, or brothers and sisters and the first cousin of the matriarch side of the family. This is considered inbreeding.

The reason it is bad is that these people have so many base pairs of genetic base pairs which are identical. Remember that genetic anomalies appear when a negative or weak gene couples with another weak gene or minus gene.

A positive gene and a positive gene you will get a positive gene.

A positive gene and a negative gene you will very likely get a positive offspring gene and only on rare, very rare occasion will a weak fault appear.

However if a negative gene and a negative gene couple then you are very likely to express a genetic flaw in offspring.

So a brother and sister will be likely carrying the same weak gene but a positive base part of the DNA pair will keep that genetic flaw subdued. However it is very likely that a coupling of their genetic code will express a genetic flaw or negative gene result. Or in other words they are way more likely to have a screwed up set of kids. So that is inbreeding.

All of us humans have relations. For instance half of Scot Irish Males have a single ancestor in the 8th century. All of us come from a single female from about 100,00 to 135,000 years ago. However that genetic code has interfaced with other DNA with enough genetic mutations to keep a healthy population.

So you are right in assuming that we are indeed all related but your term of inbreeding is to wide. Inbreeding refers to the sexual products of immediate blood relations.

Answer 4

~Well, if you are a christian and take the bible literally, we've all been doing our siblings and cousins since Pandora opened the box (oops, I mean since Eve ate the apple.) When the genes started getting too diverse, the man in the clouds started the whole process over again with Noah and his kids. No wonder we can only use about 10% of our brains. Never deduced that Mt. Ararat and Eden were really in West Virginia, did you?
Hey, cuz, you busy Saturday night?

Answer 5

I would think that what you are describing is 'outbreeding' and not inbreeding.
Another name might be evolution.
Depends from which end your perspective is aimed.

Answer 6

No there isn't any calculation that I know of cynic. But I do know that the scientist have marked the Genetic drift of D.N.A. back to the Mitochondrial Eve. This is in every human being, it is passed on to every child born from the woman.
MRCA is the Matrilineal most Recent Common Ancestor, and it goes back 140,000 years to 'AFRICA'. It is believed that she came from the area of Ethiopia, Kenya, or Tanzania.
So I suppose over the course of one hundred and forty thousand years? Yea, some inbreeding is bound to be found, here, and there.
* just a footnote here... there are about five women they believe to be the Eve's.

Answer 7

Define "inbreeding".

Answer 8

If you are looking at this from a Creationists' POV then we are all related, so the DNA % will be low and yet related... Evolutionarily speak...well you will have to look to the fish...LOL

Answer 9

probably quite a lot, considering there were no cars etc and distances were hard to cross, but it was so far back, it still doesn't explain that one goofy cousin we all have.

Answer 10

LOOKS AS IF YOU CAN WORK IT