
Archaeologists in China Discover the Oldest Stone Tools Outside Africa - montrose
https://www.nytimes.com/2018/07/11/science/hominins-tools-china.html
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victor106
TIL From the article “To determine the age of the tools, the researchers took
advantage of the planet’s changing magnetic field.

From time to time, Earth’s magnetic field flips, turning north to south.
Magnetic minerals in the soil and ocean are pushed into alignment with the
field; when they are trapped in rocks, they still point in the telltale
direction.

Geophysicists have precisely determined the timing of these magnetic flips,
which have taken place at the same time all around the world. It’s a useful
way to date the material found in layers of rock.”

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njarboe
These flips happen quickly on a geologic timescale but are not quick on a
human timescale. It takes around 1-10 thousand years for the field to flip.
The last one happened around 780k years ago. More often the magnetic field
gets quite weak for awhile, like the field is going to flip, but then the
magnetic field returns to the same strength and direction. These are called
excursions and the last one of these was likely the Laschamp excursion about
40k years ago.

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ericd
Huh, interesting. Do you know if anyone has looked at whether the rate of
genetic mutations increases during those 10k year periods of weakened magnetic
field? Seems like that would cause the magnetosphere to become less effective
at deflecting cosmic radiation.

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njarboe
Many people have looked into if these reversals can cause extinction events
and they don't appear to. Determining a change in average mutation rates seems
like something that would not be possible from the rock record. The last
reversal was so long ago that DNA does not survive well enough to do a good
study even if one had the right kind of samples to work with.

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ericd
Yeah, makes sense. I was thinking that you could look for an uptick in
biodiversity or something from the fossil record, but I'm sure it would be
tricky to separate the reasons for that.

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tomlock
As I understand it there's a strong belief amongst Chinese nationalists that
the Chinese diverged early from other humans. It makes me suspicious of this
announcement, as it may be playing to those beliefs. However, I'm not sure it
is untrue, doesn't bother me either way.

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garmaine
Well, to that end the very first sentence of this article is wrong. These
weren't carved by ancestors of anyone living today. This was homo erectus, a
distant cousin.

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alecco
Well, many Chinese scholars claim the Chinese are descendants from Homo
Erectus.

It's even shown on a BBC documentary, they get disappointed when DNA analysis
disproves their skull-shape "evidence".

[https://en.wikipedia.org/wiki/The_Incredible_Human_Journey#2...](https://en.wikipedia.org/wiki/The_Incredible_Human_Journey#2._Asia)

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garmaine
The fact that I have healthy half-chinese kids puts the nail in the coffin of
that idea... among many other things. It's about as serious an idea as a flat
earth or "intelligent design".

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rossdavidh
So, if we looked at all of the "oldest yet found" discoveries (that held up to
later scrutiny), and plotted their date vs. the date they were found, would we
see it asymptotically approaching some (presumably actual true) value? A job
for an enterprising data scientist/archaeologist out there.

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garmaine
What would that show?

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rossdavidh
Perhaps, what the actual value could be expected to be. So, for example, you
don't do a lot of work on top of the current estimates for oldest tool-using
humans outside of Africa, that is likely to be overturned in ten or twenty
years.

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garmaine
It wouldn't be convergent.

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rossdavidh
Interesting if true. I could easily believe what you say, but do we know that?
I don't know the field well enough to say.

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garmaine
Yes it is rather trivially true. The age is getting exponentially further
while discoveries are happening faster.

But that reflects improvements in technology, not anything about what’s being
measured.

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njarboe
The original Nature article published July 11[1].

[1][https://www.nature.com/articles/s41586-018-0299-4](https://www.nature.com/articles/s41586-018-0299-4)

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ggm
The 'out of africa' story gets more and more hard to sustain the longer people
look around for other stories in the emergence of modern humans. Yes, the apes
is out of africa. And then? it gets really complicated really fast.

Also, reminded of the endless jokes about who is more advanced from what
archeologists find in their own country: Americans find copper wire: invented
primitive networks. Russians find Glass threads: invented optical networks.
Irish dig up a bog and find nothing: invented wifi!

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rsynnott
“Out of Africa” refers to the theory that Homo sapiens (our direct ancestors)
came out of Africa. This article is referring to tools made by Homo erectus or
another homonid group. So, not our direct ancestors, more distant cousins.

