On 10/29/2023 9:07 PM, JTEM is my hero wrote:
RonO wrote:
You wouldn't know the where to start if you did not have the data we
have now.
That's not true. The data we had GENERATIONS ago was well in excess
of what was needed to establish interbreeding. It was simply rejected in favor of bias.
If that were true, you would likely have a very different interpretation
of what happened back then, than what actually happened. Just check
where those fossils were found. Bits and fragments that were
inconclusive, and what we know now if they had been evidence for
interbreeding it obviously did not amount to much in terms of the
genetics of the current population. Most of the Neanderthal DNA in the
current population is due to interbreeding that occurred soon after our ancestors left Africa. They took that Neanderthal DNA with them
throughout the rest of the world. The fossils in Europe whose DNA look
like they were only a few generations from their hybrid ancestor had DNA
for parts of the Neanderthal genome that were missing from most of the descendants of the initial interbreeding, and we don't have any evidence
that a significant amount of the DNA from those hybridization events
resulted in very much if any Neanderthal DNA integrated into the
population of modern humans in Europe. There was some interbreeding,
but those hybrids were pretty much dead ends, and had little impact on
the extant population genetics.
We know what humans look like right now. We know what they looked
like back then. Work it out. AND THEN test ideas.
We have the DNA data, that should tell you, that you should go with what
we have figured out after we could obtain the fossil DNA.
If we only had the data we had 30 years ago, you wouldn't know where to
start in terms of how the populations were related.
Again, not true.
Even if that data had been conclusive, it would have told you the wrong
story.
https://crosscut.com/2014/03/science-and-meaning-our-neanderthal-heritage
Google insists that he's 80. So when was he a undergraduate student?
Wanna say 50 years ago?
He doesn't understand genetics. The majority of Neanderthal DNA
segregating in the human population represents only around 20% of the Neanderthal genome. If you sequence a couple hundred people outside of
Africa you can assemble around 20% of the Neanderthal genome from the
bits that each person has. They would each have a small portion of that
20%. There isn't any Neanderthal fragments that have gone to a very
high frequency in the population. They sequenced over 200,000 Nordic
genomes and came up with around 80% of the Neanderthal genome. Most of
it was very rare, and even the common sequences are at a low frequency
in the population. Everyone doesn't have 20% of the Neanderthal genome.
Most of us have just a fraction of that 20%.
In 1975 I was an undergraduate and took Physical anthropology, and back
then there was speculation of interbreeding with more archaic Homo due
to the Australoid characteristics found in New Guinea and Australia. I
think that there was also some fossils from China that had Australoid
features. Sadly the speculation was considered to be racist even though
the brow ridges and other features had to come from somewhere. It turns
out that they may have come from Denisovans. Now that we can identify Denisovan DNA we can look into the genes responsible for those phenotypes.
So 50 years ago (plus) and undergraduate student noticed the goddamn obvious. and had to be "Taught" the wrong answer.
The thing about these characteristics is that they came from Africa. We
do not know what Densiovans looked like, but Neanderthals look
transitional between Homo erectus and Modern humans. Modern humans have
a pentagonal skull, and Neanderthals have a rounded skull that is more
football shaped like H. erectus. Neanderthals took these
characteristics with them when they left Africa 500,000 to 800,000 years
ago. You can still find variation in skull shape and things like brow
ridges segregating in the current African population, and obviously in
the population that managed to leave Africa. Some Europeans have pretty pronounced brow ridges. With the small number of fossils you can't
really tell how much variation left Africa within the last 80,000 years.
The Australoid phenotypes may have been segregating among the modern
humans that made it out of Africa, and those intermediate traits could
have just become common due to something like sexual selection for the
humans that traveled along the coast and made it into Indonesia and
Australia.
The right answer was freaking obvious, he as an undergraduate had to be "Taught"
utter bullshit.
More than half a century ago.
What did the Modern humans look like that left Africa less than 80,000
years ago? We know that the physical features have evolved. 50 years
ago, they knew this. They had categorized humans into mongoloid,
Caucasoid, and negoroid. It was sad that in the 19th century when the
racial designations were made, the racists of the day had a hard time
with the conclusion that mongoloids were the furthest from the negroid
type. When we left Africa we obviously were segregating a lot of
different phenotypic variation, and different phenotypes came to
dominant the different populations, but it turned out that the racial designations weren't really that predictive because as you might expect
all the variation was still in the different races, but were just at
different frequencies.
We do not know how much like Neanderthals some of the modern humans that
left Africa may have looked like.
And that, my dear, dear friend is not only interesting but it's something >>> that might better be "Determined" at a dinner table, or in a bar room, or >>> even at a card table like in that film "A Flock of Dodos."
That is how it used to be, but now we know how the populations are
genetically related.
We always knew they were genetically related.
Many have considered Neanderthal a sub species, Homo sapiens
neanderthalensis. The sub species designation was being kicked back and
forth back in 1975 when I took physical anthropology. They had brains
larger than extant humans. They were more robust and they had a skull
shape that looked like it was intermediate between extant humans and H. erectus.
We didn't even know that the Denisovans existed before we obtained some
of their genome sequence.
Ironically, neither did they!
We invented the distinctions. They didn't.
This is the lunatic talking. The genetic evidence indicates that
Denisovans were fully aware that they were different, and they rarely
interbred with Neanderthals. We know that they occupied the same
territories, maybe not at the same time, but sometimes there were
Denisovans in a cave and other times Neanderthals. They obviously
remained more genetically distinct from modern humans than did
Neanderthals. The paper that started this thread claims evidence of a
more recent interbreeding event 250,000 years ago between modern humand
and Neanderthals that was not shared with the Denisovans.
We're not even clear on what we mean by "Denisovans," with populations
as distantly related to each other, genetically, as they are from Neanderthals.
This seems to be wrong. Denisovan DNA came from the Altai mountains and
other samples came from places like Tibet, and they confirm a single
population so that we can tell how much Denisovan DNA is in Indonesians
and Australians. Denisovans interbred within their population
extensively and those genetics were spread around Asia, but they did not
mix very much with Neanderthals.
It turned out that Neanderthals and
Denisovans left Africa at about the same time, and became separate
populations.
I don't believe that.
That is what the genetics tell us.
It's impossible that they weren't interbreeding with existing populations, fueling their divergence.
If they had been interbreeding with Neanderthals they would not have
remained a distinct population whose genetics we can easily distinguish
from Neanderthals. How do you think that we can tell how much
Neanderthal DNA Indonesians have and how much Denisovan DNA that they
also have?
We have evidence that the modern human population or what would become
the modern human population was able to leave Africa multiple times
within the last half a million years.
No we don't. We have interpretations that say that.
We have DNA from a fossil that has Neanderthal DNA and Modern human DNA,
whose ancestors would have had to leave Africa 10s of thousand of years
before modern humans left Africa less than 80,000 years ago. That event
just didn't leave a discernible impact on the Neanderthal population.
We new Neanderthals were more closely related to modern humans than
Denisovans, and they initially thought that the mixing occurred around
300,000 years after Neanderthals had left Africa. The paper under
discussion could still be consistent with that estimate if the time Neanderthals left Africa is closer to the lower limit of 500,000 years
ago than the upper limit of 800,000 years ago. The current paper claims
that modern humans left Africa around 250,000 years ago and interbred
with Neanderthals, but could not establish a population of their own at
that time.
If they find what looks like so called "Modern" DNA, they assume a human
wave out of Africa.. instead of the other way around.
The Neanderthal population retained mostly Neanderthal DNA, it is just
that a fraction of it is from modern humans of 250,000 years ago so that fraction of their DNA is not as divergent from Modern humans than the
rest of the Neanderthal genome.
The African population originated in Eurasia.
That isn't what the DNA tells us. You should read and understand the
paper that started this thread, so that you will have a better
understanding of where the DNA was coming from in terms of Asia or Africa.
The paper that started this
thread claimed that there was a significant migration 250,000 years ago
(3 glacial periods ago) that were absorbed by the Neanderthal
population, and accounts for why Neanderthals have some DNA more closely
related to Modern humans than Denisovans.
It offered that as an interpretation.
You can't get the results by claiming Neanderthals migrated back into
Africa. Neanderthals remained Neanderthals, they just got a little bit
of modern human DNA from Africa. We can tell the parts of the
Neanderthal genome that are more closely related to modern humans, and
it is to modern humans that likely existed 250,000 years ago. The
modern humans that left Africa less than 80,000 years ago had different
DNA that had been evolving for a couple hundred thousand years since the
more ancient modern humans left Africa.
The paper is determining how much different the modern human DNA in Neanderthals is from the current African population from which that DNA
was derived 250,000 years ago (by their estimate). It isn't DNA from
extant modern humans, but Africans that existed 250,000 years ago.
None of this is fact.
Everything has to be crosschecked and verified. The estimate will
likely be refined as more African genomes are sequenced.
We have that one fossil of a
not too distant descendant of a Neanderthal and Modern Human hybrid,
that may be due to some modern humans that made it out of Africa 2
glacial periods ago, but there likely wasn't enough of them to leave a
significant genetic legacy among the Nenaderthals.
If for no other reason; there was no such thing as a "Modern human" some
250k years ago.
They were the population of Homo that existed in Africa 250,000 years
ago, and they were more closely related to Modern humans than to
Neanderthals.
Ron Okimoto
Most of the current
modern human population that exists outside of Africa have ancestors
that made it out of Africa during the last glacial period 60,000 to
80,000 years ago.
Like I said: Toba exploded some 74k years ago. Sundaland was Ground
Zero. And as that is precisely were the "Out of Asia" crowd point to as the origins of mankind, it kind of sucked for the human population there.
The entire northern hemisphere took the brunt of the Toba crisis. It was undoubtedly worse than the Younger Dryas cooling.
AFRICA was the place to be. You wanted to be as close to the equator as
you could be, and as close to water's edge. Africa offered both: The absolute
best survival odds.
But Africa is huge and it held many populations. So, which one wins?
Why, golly, the sexually selected population! The quantity-over-quality breeding strategy! They came back first, filled the void. And, they were
a lot more attractive for it, so when they did encounter others they were
in a position to sex them out of existence...
Some people are just interested in human history. What we are finding
is that a lot of the Neanderthal genetic variants that affect gene
expression have negative consequences. My guess is that the hybrids
were selected against initially and the negative variants that we still
see segregating among the current population are those of lesser
negative effects. The worst ones were likely selected out in the first
few generations after hybridization. Initially the proposal was made
that the hybrids may have had some advantage, but we haven't found a
single Neanderthal variant that has a phenotypic effect that has a high
enough frequency in the population to have mattered. If there had been
an advantage you would expect those alleles to have been maintained at a
high frequency in the population, but we all only have a couple percent
Neanderthal genetics, and each of us has a different couple percent.
Most of it only accounts for 20% of the Neanderthal genome, but when
they look at a couple of hundred thousand Nordic individuals they claim
that they can account for around 80% of the Neanderthal genome.
It's backwards. There's no reason why there should be any Neanderthal
DNA at all. But there is.
Humans rarely interact and/or bred with equality.
They certainly never did in the past.
One group was stronger. Or had better weapons. Or were more aggressive.
Or had greater numbers.
I think it's clear that Neanderthals had the upper hand. Only the spoils of war were primarily sexually selected women. So, they literally bred themselves out of existence...
All that is left are scattered bits segregating at around 50,000
base-pairs in length.
That's not necessary true at all. But, so what?
Why would you expect any?
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