Newsweek, AMNH, Molecular Clocks and Fairy Stories
richard01
supposed key events in human evolution, and Sharon Begley's article in
the latest Newsweek quotes a whole lot of them.
http://www.msnbc.msn.com/id/17542627/site/newsweek/
Whoever's briefing her has a lot to answer for, since, if both the
AMNH and Newsweek are disseminating such, the 'findings' become
engraved in stone as gospel truth in the public mind, and more than
probably, in such discussion groups as this.
Today I tried to track each one of Begley's pronouncements down to the
original paper, but came across secured access articles (particularly
in Science) which sometimes stopped me in my tracks.
But I did find one outstanding misquote, one extraordinary
interpretation of a crucial date, and a few other wilful
misinterpretations:
(Please bear with me - this is a long and detailed post, thick with
quotes, and I can't put necessary emphasis anywhere)
------------------------------
MRCA of all modern men:
Sharon Begley (Quote):
"Peter Underhill, a molecular anthropologist at Stanford University,
tracked 160 such changes in the Y's of 1,062 men from 21 populations
across the world. Applying the molecular-clock technique, he concludes
that the most recent common ancestor of all men alive today lived
89,000 years ago in Africa. The first modern humans—and therefore,
unlike the earlier wave of Homo erectus into Asia a million years ago,
the ancestors of everyone today—departed Africa about 66,000 years
ago."
Peter Underhill said nothing of the sort.
What he did say was:
"A minority of contemporary East Africans and Khoisan represent the
descendants of the most ancestral patrilineages of anatomically modern
humans that left Africa between 35,000 and 89,000 years ago.
This puts the age of M168, which marks the expansion of anatomically
modern humans out of Africa, at approximately 44,000 years, in
agreement with a previous estimate of 47,000 years with 95%
probability intervals of 35,000–89,000 years using the program
GENETREE"
Y chromosome sequence variation and the history of human populations
PA Underhill, P Shen, AA Lin, L Jin, G Passarino,+ 16 other authors
… - nature genetics, 2000
http://tinyurl.com/2h5vp8
I cannot track down Begley's 66000 year figure at all, after an
exhaustive search.
Perhaps I am missing something that someone else came up with.
----------------------------------
FOXP2
Sharon Begley (Quote):
"Using the standard molecular-clock tactic, Svante Paabo and
colleagues at the Max Planck Institute estimate that the human version
of FOXP2 appeared less than 200,000 years ago—about when anatomically
modern humans stepped onto the world stage—and maybe as recently as
50,000. If so, then it is only humans as modern as those in the last
diaspora out of Africa who developed advanced, spoken language."
The paper quoted was written by 7 authors, with Svente Paabo placed
last (that usually means a well-known authority is given some
overseeing role in the paper, not necessarily that he oversaw the
research himself).
They actually said:
"If this speculation is true, then the time when such a FOXP2 variant
became fixed in the human population may be pertinent with regard to
the evolution of human language. We estimated this time point using a
likelihood approach. Under a model of a randomly mating population of
constant size, the most likely date since the
fixation of the beneficial allele is 0, with approximate 95%
confidence intervals of 0 and 120,000 years. Our point-estimate of 0
reflects the fact that high-frequency alleles rapidly drift to
fixation, so an excess is most likely
immediately after a selective sweep.
However, if population growth soon succeeds the fixation of the
advantageous allele, the rate of drift will be decreased and high
frequency alleles may persist longer in the population. Thus, the
inclusion of population growth may push this time estimate back by at
most the time since the onset of human population growth,
some 10,000–100,000 years ago.
In any case, our method suggests that the fixation occurred during the
last 200,000 years of human history, that is, concomitant with or
subsequent to the emergence of anatomically modern humans. This is
compatible
with a model in which the expansion of modern humans was driven by the
appearance of a more-proficient spoken language"
Molecular evolution of FOXP2, a gene involved in speech and language
Wolfgang Enard*, Molly Przeworski*, Simon E. Fisher†, Cecilia S. L.
Lai†,
Victor Wiebe*, Takashi Kitano*, Anthony P. Monaco† & Svante Pa¨a¨bo*
… - Cell. Biol, 2001 - botany.utoronto.ca
http://tinyurl.com/29cv4u
- which is a quite extraordinary conclusion, based on:
"the most likely date since the fixation of the beneficial allele is
0, with
approximate 95% confidence intervals of 0 and 120,000 years."
Put less 'scientifically' this means the FOXP2 variant most probably
happened sometime between July 4 2001 AD and 120000 BC, or at most,
between 10kya and 100kya, and certainly in the last 200,000 years - a
very good series of fail-safe statements.
50,000 years ago wasn’t mentioned at all.
What it certainly doesn't say is that the FOXP2 variant was really any
'cause' for the introduction of a more-proficient spoken language, or
that it coincided in any way with appearance of modern humans, or with
any supposed intellectual explosion 50,000 years ago.
-----------------------------------
A few other wilful misinterpretations:
------------------------------------
ASPM:
Sharon Begley (Quote):
"The third, called ASPM and also involved in brain size, clocks in at
5,800 years.
That was just before people established the first cities in the Near
East and is well after Homo sapiens attained their modern form."
The researchers actually said:
"...one genetic variant of ASPM in humans arose merely about 5800
years ago"
Ongoing Adaptive Evolution of ASPM, a Brain Size Determinant in Homo
sapiens
Mekel-Bobrov et al Science 9 September 2005:Vol. 309. no. 5741, pp.
1720 - 1722
Science - (Secured article)
- abstract only
http://tinyurl.com/kmrxr
This is a bit different than stating, baldly, that something new,
ASPM, clocked in 5,800 years ago, just as we invented cities.
-------------------------------------
PDYN
Sharon Begley (Quote):
"In 2005, Matthew Rockman of Duke University and colleagues discovered
that a gene called PDYN began accumulating changes 7 million years
ago, soon after our oldest direct ancestor appeared".
The authors actually said:
"If instead of divergence, we consider the germline mutation rate,
estimated at 0.99 3 10 9 per site, and assuming 5 to 7 million years
of evolution since the last common ancestor of humans and chimpanzees,
we expect 0.34 to 0.47 substitutions per 68 bp. To convert the
acceleration factor to s, we consider the case of sequential fixations
and ignore the effect of interference among independent advantageous
mutations. The effect of interference is likely to be modest, as the
expectation of the conditional fixation time of advantageous alleles, ;
(2/s)(ln2N) , is less than 10,000 generations for s . 0.002, while the
time available for fixations is roughly 300,000 generations (6 million
years, 20 years per generation)."
Ancient and Recent Positive Selection Transformed Opioid cis-
Regulation in Humans
MV Rockman, MW Hahn, N Soranzo, F Zimprich, DB …
- biology.plosjournals.org
http://tinyurl.com/24dung
which doesn't, at all, say quite the same.
----------------------------------------
Human/chimp MRCA
Sharon Begley (Quote):
"....7 million years ago, soon after our oldest direct ancestor
appeared".
The authors of the PDYN paper cite:
Slow Molecular Clocks in Old World Monkeys, Apes, and Humans
S Yi, DL Ellsworth, WH Li - Molecular Biology and Evolution, 2002
http://www.biology.gatech.edu/professors/yi/clock.pdf
for their 7 million year date, and in turn, the authors of that paper
say:
"Next we take advantage of the recent discovery of a hominid fossil,
Sahelanthropus tchadensis (Brunet et
al. 2002), which was dated to be 6–7 MYA before present (Vignaud et
al. 2002). This is even older than the
earliest known fossil hominid so far, the Ardipithecus ramidus
kadabba, dated to be 5.2–5.8 MYA before present
(Haile-Selassie 2001). As the Sahelanthropus fossil is hominid, it
gives a minimal date of 6 MYA for the
divergence between human and chimpanzee. (Note that as long as
Sahelanthropus was a hominid, the fossil
would have postdated the human-chimpanzee divergence, even if it was
not a direct ancestor of Homo
sapiens.) We therefore obtain a maximal rate of 0.99 3 1029
substitutions per site per year for the human and
chimpanzee lineages. The actual human-chimp divergence should be older
than the Sahelanthropus hominid
fossil, which can be as old as 7 MYA (Vignaud et al. 2002). If we
assume that the date for the human-chimp
split is 7.5 MYA, then the average substitution rate in noncoding,
nonrepetitive regions becomes 0.79 3 1029
substitutions per site per year."
In other words, they fiddle their figures to fit Toumai, whose
putative date is, anyway, very embarrassing to any estimates of the
dating of the Human/chimp MRCA. And they’re not estimating the date of
the human/chimp MRCA at all, but investigating gene change rates.
-----------------------------
If Ian Tattersall is behind all this wilful misinterpretation of
reported data, to fit his own agenda, then that puts him in the same
league as Dick Cheney.
I don't think he would appreciate such a comparison at all.
regards
Richard
richard01
Chapstick
"richard01" <richard...@yahoo.com> wrote in message
news:1173686912.6...@q40g2000cwq.googlegroups.com...
I am riding a bit of a hobby horse on molecular datings linked to
supposed key events in human evolution, and Sharon Begley's article in
the latest Newsweek quotes a whole lot of them.
http://www.msnbc.msn.com/id/17542627/site/newsweek/
Whoever's briefing her has a lot to answer for, since, if both the
AMNH and Newsweek are disseminating such, the 'findings' become
engraved in stone as gospel truth in the public mind, and more than
probably, in such discussion groups as this.
Today I tried to track each one of Begley's pronouncements down to the
original paper, but came across secured access articles (particularly
in Science) which sometimes stopped me in my tracks.
But I did find one outstanding misquote, one extraordinary
interpretation of a crucial date, and a few other wilful
misinterpretations:
(Please bear with me - this is a long and detailed post, thick with
quotes, and I can't put necessary emphasis anywhere)
------------------------------
MRCA of all modern men:
Sharon Begley (Quote):
"Peter Underhill, a molecular anthropologist at Stanford University,
tracked 160 such changes in the Y's of 1,062 men from 21 populations
across the world. Applying the molecular-clock technique, he concludes
that the most recent common ancestor of all men alive today lived
89,000 years ago in Africa. The first modern humans-and therefore,
unlike the earlier wave of Homo erectus into Asia a million years ago,
the ancestors of everyone today-departed Africa about 66,000 years
ago."
Peter Underhill said nothing of the sort.
What he did say was:
"A minority of contemporary East Africans and Khoisan represent the
descendants of the most ancestral patrilineages of anatomically modern
humans that left Africa between 35,000 and 89,000 years ago.
This puts the age of M168, which marks the expansion of anatomically
modern humans out of Africa, at approximately 44,000 years, in
agreement with a previous estimate of 47,000 years with 95%
probability intervals of 35,000-89,000 years using the program
GENETREE"
Y chromosome sequence variation and the history of human populations
PA Underhill, P Shen, AA Lin, L Jin, G Passarino,+ 16 other authors
. - nature genetics, 2000
http://tinyurl.com/2h5vp8
I cannot track down Begley's 66000 year figure at all, after an
exhaustive search.
Perhaps I am missing something that someone else came up with.
----------------------------------
FOXP2
Sharon Begley (Quote):
"Using the standard molecular-clock tactic, Svante Paabo and
colleagues at the Max Planck Institute estimate that the human version
of FOXP2 appeared less than 200,000 years ago-about when anatomically
modern humans stepped onto the world stage-and maybe as recently as
50,000. If so, then it is only humans as modern as those in the last
diaspora out of Africa who developed advanced, spoken language."
The paper quoted was written by 7 authors, with Svente Paabo placed
last (that usually means a well-known authority is given some
overseeing role in the paper, not necessarily that he oversaw the
research himself).
They actually said:
"If this speculation is true, then the time when such a FOXP2 variant
became fixed in the human population may be pertinent with regard to
the evolution of human language. We estimated this time point using a
likelihood approach. Under a model of a randomly mating population of
constant size, the most likely date since the
fixation of the beneficial allele is 0, with approximate 95%
confidence intervals of 0 and 120,000 years. Our point-estimate of 0
reflects the fact that high-frequency alleles rapidly drift to
fixation, so an excess is most likely
immediately after a selective sweep.
However, if population growth soon succeeds the fixation of the
advantageous allele, the rate of drift will be decreased and high
frequency alleles may persist longer in the population. Thus, the
inclusion of population growth may push this time estimate back by at
most the time since the onset of human population growth,
some 10,000-100,000 years ago.
In any case, our method suggests that the fixation occurred during the
last 200,000 years of human history, that is, concomitant with or
subsequent to the emergence of anatomically modern humans. This is
compatible
with a model in which the expansion of modern humans was driven by the
appearance of a more-proficient spoken language"
Molecular evolution of FOXP2, a gene involved in speech and language
Wolfgang Enard*, Molly Przeworski*, Simon E. Fisher?, Cecilia S. L.
Lai?,
Victor Wiebe*, Takashi Kitano*, Anthony P. Monaco? & Svante Pa災灸o*
. - Cell. Biol, 2001 - botany.utoronto.ca
http://tinyurl.com/29cv4u
The researchers actually said:
The authors actually said:
MV Rockman, MW Hahn, N Soranzo, F Zimprich, DB .
- biology.plosjournals.org
http://tinyurl.com/24dung
which doesn't, at all, say quite the same.
----------------------------------------
Human/chimp MRCA
Sharon Begley (Quote):
"....7 million years ago, soon after our oldest direct ancestor
appeared".
The authors of the PDYN paper cite:
Slow Molecular Clocks in Old World Monkeys, Apes, and Humans
S Yi, DL Ellsworth, WH Li - Molecular Biology and Evolution, 2002
http://www.biology.gatech.edu/professors/yi/clock.pdf
for their 7 million year date, and in turn, the authors of that paper
say:
"Next we take advantage of the recent discovery of a hominid fossil,
Sahelanthropus tchadensis (Brunet et
al. 2002), which was dated to be 6-7 MYA before present (Vignaud et
al. 2002). This is even older than the
earliest known fossil hominid so far, the Ardipithecus ramidus
kadabba, dated to be 5.2-5.8 MYA before present
(Haile-Selassie 2001). As the Sahelanthropus fossil is hominid, it
gives a minimal date of 6 MYA for the
divergence between human and chimpanzee. (Note that as long as
Sahelanthropus was a hominid, the fossil
would have postdated the human-chimpanzee divergence, even if it was
not a direct ancestor of Homo
sapiens.) We therefore obtain a maximal rate of 0.99 3 1029
substitutions per site per year for the human and
chimpanzee lineages. The actual human-chimp divergence should be older
than the Sahelanthropus hominid
fossil, which can be as old as 7 MYA (Vignaud et al. 2002). If we
assume that the date for the human-chimp
split is 7.5 MYA,
yup... here is my lil' question. I don't think that the split has to
post-date all the hominid fossils because isn't it true that whatever was
"causing" our divergence... some niche pressure coupled with mutation...
could have occured more than once so that "younger" hominid fossils could
actually show up? is there any way to actually figure that out? suppose we
get a dna sample from sahel, then i guess we could.
and gadzooks! to be in the same league with Cheney... he'd better bring
along a shotgun...
--chap
circean...@gmail.com
anthropology & anatomy in college but really my interest in human
evolution goes waaaaaaay back. I'm excited to be here and to learn
from you guys :-)
A general thought about the pitfalls of molecular clocks: it
implicitly assumes that the time at which speciation occurred and the
time at which the mutation occurred are the same. In reality, it's
possible that two polymorphisms could have become established in two
different populations in the same species many many years before they
speciate. E.g., say polymorphism X became established in population 1
and polymorphism X' in population 2 at ~5 mya, but the two populations
did not become separate species until 4 mya. In this case, the
molecular clock would over-estimate the date of divergence.
Another general thought about statistics (specifically about a concept
my professor really hammered into me): the 95% confidence/probability
interval means that there is a 95% chance that the true value lies
somewhere between X and Y. It doesn't mean that 95% of the data fall
into the range [X, Y]; it also doesn't mean that a value close to the
mean/medium of [X, Y] is more likely to represent the true value. The
true value could be *anywhere* between X and Y -- the confidence
interval doesn't give you any information about where it is within
that interval. So yes, I agree with Mr. Parker that a 95% CI of 0 to
120,000 is very broad, maybe too broad to link the FOXP2 gene with
increased language sophistication with the last dispersal out of
Africa.
Onto the paleoanthropology...
I skimmed through a recent paper by Wolpoff et al. arguing that Toumai
actually represents a female proto-gorilla. What do you think of this
analysis?
Also, the last couple of papers just underline the fact that molecular
biologists *depend on the fossil record* for calibrating genetic
distances to arrive at a baseline mutation rate!
Finally, what's the feasibility of extracting workable DNA from
Sahelanthropus?
-Prionesse
Day Brown
<circean0cir...@gmail.com> wrote:
> Finally, what's the feasibility of extracting workable DNA from
> Sahelanthropus?
But right *NOW*, this spring, expeditions should be organized to hit
the arctic as it thaws out. Remember Utzi? And the Zarkov Mammoth? I
bet there are more samples of flesh that have been preserved in the
permafrost... which we all know is melting, We awta be sending drones
up there with live feeds to the internet. There'll be millions of
people checking in for a look... at really boring landscape.
But if a drone flys over anything, there's a good chance that
*somebody* will be online at the time to see it and let us know to go
have a better look.
Is there sperm in the nuts of the Zarkov mammoth?
richard01
<circean0cir...@gmail.com> wrote:
> A general thought about the pitfalls of molecular clocks: it
> implicitly assumes that the time at which speciation occurred and the
> time at which the mutation occurred are the same. In reality, it's
> possible that two polymorphisms could have become established in two
> different populations in the same species many many years before they
> speciate. E.g., say polymorphism X became established in population 1
> and polymorphism X' in population 2 at ~5 mya, but the two populations
> did not become separate species until 4 mya. In this case, the
> molecular clock would over-estimate the date of divergence.
That's a very good point, and not one, I think, that many consider
when talking about speciation.
>
> Another general thought about statistics (specifically about a concept
> my professor really hammered into me): the 95% confidence/probability
> interval means that there is a 95% chance that the true value lies
> somewhere between X and Y. It doesn't mean that 95% of the data fall
> into the range [X, Y]; it also doesn't mean that a value close to the
> mean/medium of [X, Y] is more likely to represent the true value. The
> true value could be *anywhere* between X and Y -- the confidence
> interval doesn't give you any information about where it is within
> that interval.
That excellent summary of what date ranges really mean should be
written down on everyone's shirt cuffs, and referred to every time one
of these molecular clock tales comes out.
I tried to expose one classical parasite/human legend at:
http://www.coconutstudio.com/Tapeworms.htm
(Skip the gubbins and go to the conclusions at the end)
but many palaeanthropologists (and science writers) would prefer to
maintain preconceptions backed up by almost fraudulent dating, and in
this case, lapped it up. Pat Shipman fell for it, and so did Carl
Zimmer.
The original paper has been cited 23 times in other research papers,
so I guess a lot of others fell for it, too.
The date that really caused excitement in this case was -1.71Mya (just
about the time when H. erectus came on the scene). Trouble was that
this particular estimated date was in a 95% confidence zone stretching
from -240kya back to infinity (ie somewhat before the Big Bang).
To add insult to injury, that non-existent date was then used as the
earliest of a supposed date range.
regards Richard
Prionesse
As we all know, fossilization replaces the organic content of bone
with minerals. DNA also degrades over time. DNA in the living cell is
always being repaired, and in death, bases tautomerize, the helix gets
cleaved at random places ... basically anything that disrupts hydrogen
bonds will denature DNA. I define a "workable" segment of DNA as a
sufficiently long segment of intact base pairs so that you could
amplify it with PCR. It would also need to be sufficiently long to
give you some idea of its location on a hominoid chromosome, and then
you could compare how readily it hybridizes with the corresponding
region of DNA from chimps and then from humans. Ideally, the segment
would come from a coding region since our time frame (6-7 mya) is
rather long, and coding regions accumulate mutations more slowly and
have less base-pair inversions than non-coding regions.
Chapstick
still... it is more fun to think that SOME THING will give us definitive
dates so that we can piece together this puzzle... perhaps during our
generation? naaah... i guess it will be several more generations down the
line before we "know" how humans evolved.
do you give any credence to molecular dating, or is it now all
hocus-pocus? I thought that Gerritt, and Phillip, and some other folks had
done some significant work with molecular dating?
regards,
chap
ps... welcome Prionesse
>
>
> regards Richard
>
>
Chapstick
"Prionesse" <circean...@gmail.com> wrote in message
news:1173927104.8...@l75g2000hse.googlegroups.com...
While it is unlikely with our current fossil collection (meaning all the
hominid fossils that have been recovered) that we will find soft tissue or
even DNA, here is an article about dino soft tissue:
(laters, chap)
http://www.sciencenews.org/articles/20050326/fob1.asp
Paleontologists usually find only a creature's hard body parts, such as
bones, teeth, or shells, preserved as fossils. In the rare instances when
internal organs, muscles, skin, and other soft body parts turn up, the
original tissue has been replaced by minerals that create hard replicas,
says Mary H. Schweitzer, a paleontologist at North Carolina State University
in Raleigh. Sometimes, a soft tissue's shape is recorded by sediments that
surround it.
Now, the first report of flexible material from a fossil describes an
extraction from the femur, or upper leg bone, of a T. rex that lived about
68 million years ago in what is now Montana.
The researchers dissolved minerals from the fossil by soaking it in a series
of slightly alkaline solutions. After a week, much of the remaining material
was surprisingly soft and pliable, say the researchers. Many parts of the
remains were translucent and fibrous, and they retained their elasticity
after repeated cycles of dehydration and rehydration. Schweitzer and her
colleagues report their findings in the March 25 Science.
Some stretchy, translucent samples were high in carbon and appeared to be
part of a network of blood vessels, says Schweitzer. Similar
demineralization experiments on modern-day ostrich bones-with an added step
required to digest the collagen strengthening those bones-yielded blood
vessels of a similar size and texture, she reports.
The researchers squeezed round, microscopic structures out of the presumed
T. rex blood vessels. Those small spheres, which ranged from dark red to
deep brown, may be red blood cells, says Schweitzer.
Also, some fibrous remains contained small, elongated features that look
like cells called osteocytes, which are found in mature bones.
Finally, a spongy material extracted from the bones triggered a chemical
response in tests to detect proteins commonly found in bones of modern
chickens and cows.
Using the extraction technique, Schweitzer and her colleagues subsequently
recovered what appear to be blood vessels and osteocytes from two other
well-preserved specimens of T. rex. They've also obtained osteocytes from an
80-million-year-old hadrosaur, a plant-eating dinosaur.
The state of preservation noted in the new study is "improbable but
obviously not impossible," says Cameron J. Tsujita, a paleontologist at the
University of Western Ontario in London. The osteocytes are "dead ringers"
for those present in living vertebrates, he notes. As for the purported
blood cells, he says that he "can't really think of what else they could
be."
This is a "totally novel discovery," says Derek E.G. Briggs, a
paleontologist at Yale University. The tissue preservation that Schweitzer's
team has described may be more commonplace than scientists might expect, he
says.
Additional analyses of the T. rex fossils, as well as of material from other
specimens, could provide insight into the early stages of fossilization,
says Briggs. Such information may also reveal new details of dinosaur
physiology and metabolism.
Week of March 26, 2005; Vol. 167, No. 13 , p. 195
Science News
Prionesse
Now whether paleoanthropologists can get permission to do this kind of
work on a hominid fossil, jealously guarded by the National Museums of
[Insert African Country Here] is another matter. I can imagine the
museum administration is already wary of foreigners from wealthy First
World nations (ex-colonialists in their eyes) digging up precious
national relics and monopolizing their study & interpretation (because
let's face it, most published paleoanthropologists are still
Westerners). Also, by soaking a fossil in alkaline solution then
hydrating and re-hydrating it would probably destroy a lot of the
anatomy preserved by the minerals. Of course you'd make a cast before
destroying the fossil but even the best casts are never 100% faithful
replicas.
richard01
> "richard01" <richardparke...@yahoo.com> wrote in message
as anyone, that real answers will come from the mass of scientific
investigations going on that are teasing out details of how humans
evolved.
What I do object to, strongly, is a sort of 'politically-correct'
story being widely accepted, and then genetics scientists and others
massaging their results to fit the legend. (You don't have to be a
rocket scientist to see how it's done - go into the small print of the
original papers, and occasionally replay the logic to yourself).
I can remember, as a child, being hugely impressed by seeing the
Piltdown skull sitting there, like King Tut's jewels in a special case
in one of the Kensington museums, and being awfully impressed by how
much scientists had learned about human evolution from just a couple
of bone fragments that turned out (actually a few months before I saw
it), as fakes.
With genetics studies, the order in which things happened, or how
things split, can, I think, be revealed, but to go beyond that, and
stick dates onto that order is beyond current possibility.
You haven't really got any calibration of mutation rates (Hoberg used
as 'parallel mutation rates' hammerhead sharks, snapping shrimps, and
crabs, whose 'species differentiation' was defined by the closing of
Panama umpteen millions of years ago).
I haven't seen much of Philip's or Gerrit's recent work, but I believe
they both have their heads screwed on properly, and have enough
expertise in basic maths not to publish spectacular results that can
be undone in a few moments by an innumerate like me.
It all comes down to basic native geometry. If you draw two exactly-
known lines on a graph, and they intersect at a definite point, then
OK.
If they are so close together that the intersection point, added to
the uncertainty of where exactly the lines should be anyway, leaves
you with a huge target area, it does nobody any good for you to claim
that the centre point of that huge target area is THE DATE.
For an interesting discussion of the perils and pitfalls of DNA
sampling, see:
1 million base pairs of Neanderthal DNA at:
http://www.nature.com/nature/journal/v444/n7117/pdf/nature05336.pdf
regards
Richard Parker
Siargao Island, The Philippines.
My website at www.coconutstudio.com is about the island and its
people, coastal early humans, fishing, coconuts, bananas and whatever
took my fancy at the time.
Day Brown
in the DNA of hermaphrodites who are XXY, not XX or XY.
Turns out, there is no "moment of conception", but a period of time
while the ovum shell is permeable, and sometimes more than one sperm
gets in. If both are XX or XY, no biggie, the conception looks like
ordinary XX or XY, and nobody notices the diff.
But we know from "Sperm Wars" that both sperm dont even havta be from
the same donor. Thus if there's a mismatch between Homo Sapiens and
Homo Neanderthal or Homo Erectus, there can still be viable
progeny.... who have incorported snippets of DNA from whatever is
available. Turns out DNA dont join together like the zipper on a new
jacket, but more like an old one, that has loops hanging out there
that get joined with whatever fits, from whatever sperm donor.
thus, there is no single progeniture sperm donor altho the mtDNA is
directly linear. And thus SE Asia seems to have some snippets of
Erectus, and Europe has snippets of Neanderthals. Which account for
the white skin, blue/green eyes, big noses, shorter forelimbs, heavy
beards, and other such HNS traits. It also explains why there are only
seven mtDNA lines distributed across Europe. The hybridization
process, as you'd expect crossing two different species works far more
reliably with males whereas the females can have really deadly
birthing problems. Which wiped out most of the mtDNA lines there.
Sykes, "The Seven Daughters of Eve" reported that all the mtDNA in
europe date from 10kya to 50kya. The thing about that latter date,
50,000 years ago, is that the only mtDNA in Europe at that time was
*Neanderthal*. When you have an evolutionary process this mixed up, I
dont see how you can determine when various haplotypes emerged.
jllyz32248391350
> I am riding a bit of a hobby horse on molecular datings linked to
> supposed key events in human evolution, and Sharon Begley's article in
>
> This is a bit different than stating, baldly, that something new,
> ASPM, clocked in 5,800 years ago, just as we invented cities.
> -------------------------------------
> PDYN
>
> Sharon Begley (Quote):
> "In 2005, Matthew Rockman of Duke University and colleagues discovered
> that a gene called PDYN began accumulating changes 7 million years
> ago, soon after our oldest direct ancestor appeared".
>
> The authors actually said:
>
> "If instead of divergence, we consider the germline mutation rate,
> estimated at 0.99 3 10 9 per site, and assuming 5 to 7 million years
> of evolution since the last common ancestor of humans and chimpanzees,
> we expect 0.34 to 0.47 substitutions per 68 bp. To convert the
> acceleration factor to s, we consider the case of sequential fixations
> and ignore the effect of interference among independent advantageous
> mutations. The effect of interference is likely to be modest, as the
> expectation of the conditional fixation time of advantageous alleles, ;
> (2/s)(ln2N) , is less than 10,000 generations for s . 0.002, while the
> time available for fixations is roughly 300,000 generations (6 million
> years, 20 years per generation)."
> Ancient and Recent Positive Selection Transformed Opioid cis-
> Regulation in Humans
> MV Rockman, MW Hahn, N Soranzo, F Zimprich, DB …
>
> which doesn't, at all, say quite the same.
> ----------------------------------------
> Human/chimp MRCA
>
> Sharon Begley (Quote):
> "....7 million years ago, soon after our oldest direct ancestor
> appeared".
>
> The authors of the PDYN paper cite:
>
> Slow Molecular Clocks in Old World Monkeys, Apes, and Humans
jllyz32248391350
jllyz32248391350
> supposed key events in human evolution, and Sharon Begley's article in
>
> This is a bit different than stating, baldly, that something new,
> ASPM, clocked in 5,800 years ago, just as we invented cities.
> -------------------------------------
> PDYN
>
> Sharon Begley (Quote):
> "In 2005, Matthew Rockman of Duke University and colleagues discovered
> that a gene called PDYN began accumulating changes 7 million years
> ago, soon after our oldest direct ancestor appeared".
>
> The authors actually said:
>
> "If instead of divergence, we consider the germline mutation rate,
> estimated at 0.99 3 10 9 per site, and assuming 5 to 7 million years
> of evolution since the last common ancestor of humans and chimpanzees,
> we expect 0.34 to 0.47 substitutions per 68 bp. To convert the
> acceleration factor to s, we consider the case of sequential fixations
> and ignore the effect of interference among independent advantageous
> mutations. The effect of interference is likely to be modest, as the
> expectation of the conditional fixation time of advantageous alleles, ;
> (2/s)(ln2N) , is less than 10,000 generations for s . 0.002, while the
> time available for fixations is roughly 300,000 generations (6 million
> years, 20 years per generation)."
> Ancient and Recent Positive Selection Transformed Opioid cis-
> Regulation in Humans
> MV Rockman, MW Hahn, N Soranzo, F Zimprich, DB …
>
> which doesn't, at all, say quite the same.
> ----------------------------------------
> Human/chimp MRCA
>
> Sharon Begley (Quote):
> "....7 million years ago, soon after our oldest direct ancestor
> appeared".
>
> The authors of the PDYN paper cite:
>
> Slow Molecular Clocks in Old World Monkeys, Apes, and Humans