Forgotten history: The first Thanksgiving in Texas

[Oldgringo]

What does all this have do with the "an ape is your daddy" question?

[DoubleJ]

I thought I was the king of thread drift....

[Purplehood]

I am thinking that instead of putting my ethnicity on any documents, I will simply provide my genetic markers as described above. Actually, that is pretty fascinating.

[Skiprr]

I thought I was the king of thread drift....

I'll be conducting a thread-drift clinic at the next TexasCHLforum day event at PSC. It's titled, "How to Completely Derail a Topic in 50 Words or Less." I'll have a co-instructor for the 50-word part. I never seem to manage that...

I am thinking that instead of putting my ethnicity on any documents, I will simply provide my genetic markers as described above.

Ya know, to further derail this thread, after I posted that last one, I regretted not clarifying something.

There are two reasons the Y-chromosome has proven so valuable in anthropological and genealogical genetic studies. The first reason is that it is passed only from father to son. Females don't carry the chromosome, so it provides an unbroken patrilineal chain.

The second reason is something every woman instinctively knows: most of the Y-chromosome is just junk. Genetic mutation at the chromosome level happens all the time. For genes that control or influence things like inherited diseases, obviously a single mutation might make a huge difference in the survivability of an individual. Conversely, the Y-chromosome has very limited functionality: basically, it's just a switch that's either there or not, making the baby either male or female.

But there's a lot of material along the Y-chromosome, and geneticists actually refer to it as "junk" because it serves no real purpose. Since the human genome was mapped in 2000, scientists have (and continue to do so) determined which markers change (mutate) more quickly than others, and have been able to establish the relative age and anthropological origins of those mutations. Since the mutated markers have no affect on the individual's biological characteristics, the mutations are free to occur over tens of thousands of years without jeopardizing the health of the future generations.

Interesting stuff to geeks like me. But it's important to remember that this patrilineal line is just one line in an individual's complex pyramid of genetic inheritance. The numbers don't work out quite this precise, but it's nevertheless accurate to think of it this way: you are a 50/50 amalgam of the genetic material from your father and mother. In turn, they were 50/50 from their fathers and mothers so, logically, you are 25% the DNA of your grandparents.

The "dilution" of your genes continues back in time, doubling with each generation of combinant DNA. You are 12.5% of each of your great-grandparents, and 6.25% of your great-great-grandparents. So if we assume, conservatively, that one generation is 30 years, to get back just to the Revolution in 1776 you need almost 8 generations. Circa 1770, you had 128 ancestors that contributed genetic stuff to who you are today; you get 0.78125% of your DNA from each of these ancestors. At 20 generations, you get 0.00019% of your DNA from each of your ancestors. Coincidentally, that puts us at 1409, the year Henry IV was finally able to recapture Wales.

Now extrapolate that back 10,000 years to population migrations in anthropological timeframes and the math gets really tricky. We can't tell when, but at some point in that geometric progression of your own ancestral population, the funnel changes shape and narrows again, arriving at the time when our long-lost hunter-gatherer ancestors ventured out of the Rift Valley into northern Africa, then across into the Fertile Crescent.

My father's line is Welsh, and goes back to the population that came up the Iberian Peninsula after the last "little" ice age and then settled ancient Britain. It does define my patrilineal origins, but I could just as easily have those markers and think of myself as, say, Chinese because I might have far, far more ancestors who came from the populations who moved into China.

If anything, in fact, getting involved in this has really driven it home to me that everyone in the world really is related. We are, very literally, all cousins, and we think of ethnicity far too narrowly. Someone who might strongly announce himself as African American might trace his patrilineal line back to haplogroup I, the "Viking haplotype." Someone whose self-identity is French may descend from a South Asian male ancestor. And we really do all descend from a male who lived in the Rift Valley of Africa.

Okay. Kumbaya.

Now back to my normally curmudgeonly self...

[Oldgringo]

So? Apes it is...huh?

[aardwolf]

Some of my ancestors came here before Leif Ericson and some came after but I was born in this country so I'm a Native American.

[seamusTX]

The second reason is something every woman instinctively knows: most of the Y-chromosome is just junk.

What about the AR-15 gene, the golf gene, the football gene, the fishing gene, the tool gene, the not-asking-directions gene (nAdq3), and the leaving-the-seat-up (ltSujerk4) gene?

I think I see some sexism here.

The "dilution" of your genes continues back in time, doubling with each generation of combinant DNA. You are 12.5% of each of your great-grandparents, and 6.25% of your great-great-grandparents. So if we assume, conservatively, that one generation is 30 years, to get back just to the Revolution in 1776 you need almost 8 generations. Circa 1770, you had 128 ancestors that contributed genetic stuff to who you are today; ...

You are ignoring the fact of crossing. Very few people have 2 to the power n ancestors beyond their grandparents. At a certain point in the past, many of their great-great-et cetera grandparents were the same people in different branches.

It has to be that way. The six billion people alive today had a million ancestors at some point, and ultimately only two.

Thanks, everybody, for totally, completely derailing my thread, which I did not mean to be controversial.

- Jim

[Skiprr]

So? Apes it is...huh?

You posted twice and I didn't respond. Sorry. But I'm not sure why apes are in the picture. I never said anything about creationism versus evolution. No chimpanzees involved.

The genetic evidence that's surfaced during the past eight years is interesting because it can clearly delineate the oldest DNA of the modern human, Homo sapiens sapiens to be exact, and it can place the origin of that DNA in the area of the African Rift Valley.

Not talkin' "cavemen" or "early hominids" or Neanderthals here. Homo sapiens sapiens is us: same anatomy, same skeleton, same body hair, same hands, same eyes, same cranial size, same DNA. And most assume the same capacity for intelligence and emotion. Homo sapiens sapiens is genetically distinct, that's why the DNA can be traced back in time with certainty...well, a few thousands years here or there in that timeframe is pretty certain.

The Rift Valley starts in the north at the Dead Sea Transform in what is today Lebanon. The Rift runs south, dividing the Golan Heights and Galilee Mountains. This is the headspace of the Jordan River that flows into the Sea of Galilee in Israel, then continues to the Dead Sea. From there, the Rift runs the length of the Red Sea, then follows the Nile south.

The DNA evidence says we all share the same male ancestor who lived somewhere in this area at least 120,000 years ago. This is the first point in time where the DNA of Homo sapiens sapiens appears. With a nice salon and haberdashery makeover, you wouldn't be able to pick him out in any business crowd today...though he might be a bit more physically fit than the average 21st century city-dweller.

One interesting thing to me is that the DNA evidence can, I believe, support more than one worldview. You can draw your own conclusions.

You are ignoring the fact of crossing. Very few people have 2 to the power n ancestors beyond their grandparents. At a certain point in the past, many of their great-great-et cetera grandparents were the same people in different branches.

Nope; didn't ignore it. Sorta swept it under the rug, though. I said, "The numbers don't work out quite this precise[ly], but it's nevertheless accurate to think of it this way..."

Combinant alleles are never really a 50/50 contribution from your parents. It's a crap shoot about which genes are transferred and from whom, including factors like each parent's mix of dominant and recessive genes. You can look at a family of 15 kids all from the same mother and father and readily tell they're all different. Even direct inbreeding will result in different DNA combinations in each individual offspring. Heck, even identical twins don't have identical genomes.

So when you go back even a few generations and find the same ancestor in a couple of places on your family tree, the fact is that you're dealing with the specific DNA they pass along at each of those singular birthing events, and it's never the same twice. This is an amazingly efficient way to assure that genetic diversity, and therefore species survival, can be created from even a limited population.

I don't know if anyone has actually tried to work out the precise probability of DNA contribution by generation--or even if that could be done with any degree of accuracy beyond a generation or two--but most people accept that the median and mean of that probability will fall pretty close to a simple factor of .5 per ancestor per generation.

And you're right: my analogy of two funnels matched big-end to big-end, with our first Rift Valley ancestor on one and you at the other, was also imprecise...and unrealistic. But now I wish I'd stated it that way because it makes a better visual.

Fact is, of course, over the timeframes involved, local populations waxed and waned, wars and famine and disease intervened, entire populations were eradicated. Thank goodness we had that complex mechanism of DNA combination working for us, or small tribes of people could never have grown appreciably.

As you say, the billions of people alive today ultimately stem from only two (studies of the matrilineal lines employ mitochondrial DNA, but that a whole 'nother subject). Even the large scale diasporas are complex, but at an individual level it's almost unfathomable.

Sit back and contemplate how you, John Doe, got from point A, some 120,000+ years ago, to point B, a TexasCHLforum member in 2008 Texas.

Every single one of your ancestors, both mother and father of that particular generation, had to survive to childbearing age, have a child, and have that child survive to childbearing age to begat another child who also survives. Talk about a dauntingly improbable chain of events.

We're talking at least 4,000 generations here, probably more like 5,000. Continental glaciations, floods, conflagrations, pestilence, wars. Heck, even if you broke a leg 90,000 years ago you were probably a goner in a matter of days. And with limited tools, your ancestors had to walk out of the Rift Valley to, literally, the four corners of the earth (yeah, rafts came into play, too; can you imagine setting off on a raft in the Pacific Ocean tens of thousands of years ago with no clue whatsoever about what you'll find, or even if you'll survive a single day?).

How many extremely close calls did each one of your thousands upon thousands of ancestors have to escape for you to be here today? It's kinda like looking through a telescope and understanding for the first time how big the universe really is.

Thanks, everybody, for totally, completely derailing my thread, which I did not mean to be controversial.

I apologize. And I owe you a box of FMJ 9mm, .40 S&W, or .45 ACP; your choice.

But, hey, you did post: "The whole conquest and colonization was an ugly business, but unless you are a Native American, you wouldn't be here otherwise. Every one of us stands at the summit of a pyramid of violence and bloody conflict that our ancestors survived."

Correct as it is, that seems like it may have had openings for controversy.

My whole tirade launched from the "who's a Native American" thing.

I promise to write shorter posts in the future.

Maybe.

If I can control myself.

[seamusTX]

And I owe you a box of FMJ 9mm, .40 S&W, or .45 ACP; your choice.

Nah, this is almost as much fun as arguing whether grits or biscuits and gravy are better.

- Jim

[Oldgringo]

Jim, I think Skiprr is right.

[DoubleJ]

And I owe you a box of FMJ 9mm, .40 S&W, or .45 ACP; your choice.

Nah, this is almost as much fun as arguing whether grits or biscuits and gravy are better.

- Jim

Well, that depends. You take some grits, put an egg over medium in there, crunch up a couple o' pieces of bacon...

[aardwolf]

Grits are good with shrimp. Charleston style.

[Oldgringo]

Grits are good with shrimp. Charleston style.

"What's a grit" from My Cousin Vinny

[aardwolf]

"What's a grit" from My Cousin Vinny

I always wondered why they didn't tell him it was like polenta.