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Archaeologists in China Discover the Oldest Stone Tools Outside Africa

nytimes.com

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Re: Archaeologists in China Discover the Oldest Stone Tools Outside Africa

#11

Post by hyperpallium »

victor106 wrote: post #4

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…

Funfact: key evidence for the theory of tectonic plates was the changing magnetic field direction in rocks with distance from their magma source.

Always seemed like one fantastical theory being supported by another fantastical theory. (Don't worry, I'm not a tectonic skeptic.)

Re: Archaeologists in China Discover the Oldest Stone Tools Outside Africa

#12

Post by njarboe »

victor106 wrote: post #4

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…

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.

Re: Archaeologists in China Discover the Oldest Stone Tools Outside Africa

#13

Post by Pica_soO »

njarboe wrote: post #12
victor106 wrote: post #4

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…

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 like…

Super interesting, thanks for posting about the Laschamp Event

Re: Archaeologists in China Discover the Oldest Stone Tools Outside Africa

#14

Post by ericd »

njarboe wrote: post #12
victor106 wrote: post #4

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…

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 like…

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.

Re: Archaeologists in China Discover the Oldest Stone Tools Outside Africa

#15

Post by alecco »

garmaine wrote: post #6
tomlock wrote: post #5

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.

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.

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...

Re: Archaeologists in China Discover the Oldest Stone Tools Outside Africa

#16

Post by tomcam »

Pica_soO wrote: post #13
njarboe wrote: post #12

Earlier quoted context omitted.

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 like…

Super interesting, thanks for posting about the Laschamp Event

We are Laschampions.

Re: Archaeologists in China Discover the Oldest Stone Tools Outside Africa

#17

Post by rsynnott »

ggm wrote: post #2

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 thr…

“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.

Re: Archaeologists in China Discover the Oldest Stone Tools Outside Africa

#18

Post by njarboe »

ericd wrote: post #14
njarboe wrote: post #12

Earlier quoted context omitted.

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 like…

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.

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.

Re: Archaeologists in China Discover the Oldest Stone Tools Outside Africa

#19

Post by laretluval »

johnzim wrote: post #9
laretluval wrote: post #8

Earlier quoted context omitted.

I don't think even the strongest Chinese nationalist would claim that the Chinese diverged from everyone else 2 million years ago!

Actually there was a very significant amount of money ploughed into researching that exact topic in the PRC. With significant and predictable sadness when the results didn't go their (the CCP and Chinese nationalists) way. A google search gives a good paper on the topic: https://core.ac.uk/download/pdf/28941533.pdf TLDR: CCP, seeking to shore up ethno-nationalism (not an especially rare occurance in Chinese history)…

Homo erectus pekinensis isn't 2 million years old.

Go back 2.1 million years, like these stone tools, and it's not even clear that there is a genus Homo.

Re: Archaeologists in China Discover the Oldest Stone Tools Outside Africa

#20

Post by ericd »

njarboe wrote: post #18
ericd wrote: post #14

Earlier quoted context omitted.

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.

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.

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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