CX

I don't want to derail this thread but I've long had trouble getting my mind around this mitochondrial "Eve" notion. Most of the popularizations I've read seem to imply that our mitochondrial DNA indicates that all living humans have one common female human ancestor. I gather from the gobbledygook above that that is not exactly what theories about mtDNA say or imply. Let me see if I've got this right. If I look at my genealogical tree going back say 20 generations there are somewhere around 1,048,576 individuals who are my ancestors and potentially contributed genetic material to me. What the mtDNA thing shows is that one of those individuals' particular alleles at a particular locus made it all the way to my DNA. Am I close? This is a very difficult concept for the layman and one that is regularly misused by creationists.

Roland98

I don't want to derail the thread either, but I missed on the first go-round. Thought this was amusing, from the "instructions to potential authors" page:

Also wondering if any real scientist has ever submitted an article as a joke--some work of complete B.S. to see if it would get in under the radar, to show what a joke the TJ is? Would be very amusing...

This also cracked me up:

Couldn't have said it better myself...

anakata

Yes. Look up the Sokal hoax.

Shpongle

What's so funny about that? They don't seem to be referring to scientific terms. They are simply talking about being concise. Pick up any book on writing and you'll see the same thing.

Roland98

The part I bolded--"avoid big words." Contrast this to the instructions for authors of any science journal--certainly, brevity and conciseness are important and technical jargon should be explained, but the "avoid big words" sentiment succintly says that this journal is not aimed to scientists by any stretch of the imagination. Actually, one reason it struck me as amusing is because I received almost verbatim instructions for a reference book I wrote--which is geared to upper-level high schoolers, but was to be written at a 9th-grade level.

Anyway, as I said, just a comment that has little to do with the way the thread has evolved.

Roland98

lol. I'm familiar with the Sokal hoax--and think it would work even more brilliantly in the creationist journals. Sokal sent a mathematics/physics related paper to a humanities journal--stupid move on their part that they didn't bother to consult any actual physicists or mathematicians--but if a hoax article was sent to TJ, with the subject being Biblical creationism and throwing in some bastardized (or heck, made up) science to support it--would they catch it? Or would they accept and publish the paper?

Jayjay

Like I said earlier in this same thread, I think it wouldn't be as easy. If there's anything AiG is good at, it's lying through their teeth and committing hoaxes like this (for example, by submitting undatable rocks to radiometric dating labs and then making noise about it). It would take a lot more commitment and skill than Sokal's hoax to beat AiG in their own game.

anakata

Ah. Sorry :-). I read a bit too quickly...

Peez

You are close, let me elaborate. I will start with a modification of the model that RufusAtticus employed:

Let's say we start out with a population of 6 individuals, each with 3 loci (A, B, and C). At each locus there are 2 alleles, so there are 12 alleles at each locus (we will assume that they are all different). Now when they reproduce to form the next generation, by chance some of these 12 alleles at each locus might not be passed on. So in the next generation of the original 12 alleles at locus A, only 10 or 11 remain (the same kind of thing will be happening at the other loci). The population reproduces again and more alleles are lost, say only 9 of the original alleles remain at locus A (with something similar happening at loci B and C). This will continue until only one of the original 12 alleles are left at locus A (the same thing is happening at the other loci, but not necessarily at exactly the same rate). Here are the results of an example I wrote in Excel. Each line is a generation, each letter represents a locus, and each number represents an allele at that locus.

(first column is generation number, alleles then separated by spaces)

gen locus A
0 1 2 3 4 5 6 7 8 9 10 11 12
1 3 6 12 11 7 3 2 7 3 3 2 4
2 4 6 3 3 3 6 3 2 2 7 3 7
3 3 3 6 2 3 4 3 7 2 2 3 7
4 7 7 3 2 4 4 6 2 7 3 4 3
5 3 3 4 3 3 4 3 4 7 7 2 7
6 3 7 3 7 3 3 3 4 3 3 3 3
7 3 7 3 3 3 3 3 3 3 3 3 4
8 3 3 3 3 3 3 3 3 3 3 7 3
9 7 3 3 3 3 3 3 3 7 3 3 3
10 3 3 3 3 3 3 3 3 3 3 3 3
11 3 3 3 3 3 3 3 3 3 3 3 3
12 3 3 3 3 3 3 3 3 3 3 3 3
etc.

gen locus B
0 1 2 3 4 5 6 7 8 9 10 11 12
1 2 10 6 2 11 1 7 3 12 11 5 4
2 5 7 6 5 12 5 5 11 4 10 4 1
3 4 6 4 4 5 5 6 5 6 4 4 5
4 6 4 4 5 4 4 4 5 4 4 6 4
5 5 4 4 4 4 4 4 4 5 5 4 4
6 5 4 4 4 4 4 4 4 4 4 4 4
7 4 4 4 4 4 5 4 4 4 4 4 4
8 4 5 4 4 4 4 4 4 4 4 4 4
9 4 4 4 4 4 4 5 4 4 4 4 4
10 4 4 4 5 4 4 4 4 4 4 4 4
11 4 4 4 4 4 4 4 5 5 4 4 4
12 5 4 4 4 5 4 4 5 4 4 5 4
13 4 4 5 4 5 5 4 5 5 4 4 4
14 5 5 4 5 4 4 4 5 4 4 4 5
15 4 4 4 5 5 4 4 4 4 4 5 5
16 4 4 5 4 5 4 5 4 5 4 4 5
17 5 4 5 4 4 4 4 5 5 5 4 4
18 4 5 5 4 5 4 4 4 4 4 5 4
19 4 4 5 4 5 4 4 4 4 4 5 4
20 5 4 5 4 4 4 4 4 4 4 4 4
21 4 4 4 4 4 4 4 4 4 4 4 4

gen locus C
0 1 2 3 4 5 6 7 8 9 10 11 12
1 11 1 9 12 9 10 11 11 7 3 7 11
2 11 11 11 7 11 11 11 11 7 3 7 7
3 7 11 11 7 11 7 11 7 7 7 7 7
4 11 7 7 11 7 7 7 7 7 7 7 11
5 11 11 7 11 7 7 11 7 11 7 7 7
6 11 7 11 7 11 11 7 7 11 7 11 11
7 11 7 7 7 7 11 11 7 7 11 11 11
8 7 11 11 11 11 11 7 11 7 11 11 7
9 11 11 11 7 7 7 7 7 11 11 11 11
10 7 11 11 11 11 7 11 7 7 11 7 7
11 7 7 11 7 11 11 7 7 7 11 11 11
12 7 11 11 7 11 11 11 11 7 7 7 7
13 7 7 7 11 11 11 7 7 11 11 7 11
14 11 7 11 7 11 11 11 7 7 11 7 7
15 11 11 7 11 7 7 11 11 11 11 11 11
16 11 11 11 11 11 11 7 11 11 11 11 7
17 11 7 11 11 11 11 11 11 11 11 11 11
18 11 11 11 11 11 7 11 11 11 11 11 11
19 11 11 11 11 11 11 11 11 11 7 11 11
20 11 11 11 11 11 11 11 11 11 7 11 11
21 11 11 11 11 11 11 7 7 11 11 11 11
22 11 11 11 11 7 11 11 7 11 11 11 11
23 11 7 7 11 11 7 11 11 11 11 11 11
24 7 11 11 7 11 11 7 11 11 11 11 11
25 11 11 11 7 11 11 11 11 7 11 11 11
26 11 11 11 11 11 11 11 7 11 11 11 7
27 11 7 11 11 11 11 11 11 11 11 11 11
28 11 11 11 11 11 11 11 11 11 11 11 11

As you can see, only the "3" allele, or rather its descendants, remains at the A locus in the population after 10 generations (we are ignoring mutations here). Note that after 10 generations the "4" and "5" alleles persisted at the B locus, and the "7" and "11" alleles persisted at the C locus. Remember that these are the same population, the same individuals. For example, one individual from the population after 10 generations might have "3" and "3" at locus A, "4" and "4" at locus B, and "7" and "11" at locus C.

After 28 generations all three loci have coalesced. At that point we might state that the entire population may be traced back to one individual who had the "11" allele at locus C who was alive 28 generations ago, but clearly this is quite different from claiming that we have descended from only one person who was alive 28 generations ago.

The same concept applies to mitochondrial (mt) DNA, but the situation is slightly different. Most of your DNA is found in the nuclei of your cells, and you inherit it from both your parents (about half from each). Mitochondria (organelles found in the cytoplasm of your cells) have a small amount of their own DNA. Since mitochondria are not usually passed on to the egg from the sperm, you generally inherit all of your mitochondria from your mother, and so all of your mtDNA. This makes mtDNA easier to track: it is not being mixed and resorted each generation. There are a number of loci in the mtDNA, but since they tend to be inherited all together or not at all (you either get the mitochondrion or you don't), we can trace the coalescence of the entire mtDNA rather than that of a particular allele.

So, we can estimate that all living persons inherited mitochondria that are the descendants of one particular woman who lived so many years ago, but perhaps we also inherited a haemoglobin allele from some other woman alive at that time, and an insulin allele from yet another, etc. Another way to look at it is that at some time in the future, the mtDNA from only one woman alive today will likely persist. At the same time, there will be the descendants of many other women alive today.

I hope that this makes sense.

Peez

CX

Indeed. Thanks ever so much. If I might rephrase in more general "genetics for dummies" terms. What this is basically telling us is that one small portion of the genetic makeup of all living humans derives from a single female ancestor in the past. So basically I know that x years ago a woman contributed genetic material to my DNA that I share with everyone else, but many different women are our direct line ancestors.