Home
登錄
註冊
學習內容
Loading...
These Petroglyphs Helped Humans Survive the Desert - Video học tiếng Anh
聽力練習
聽力練習
/
Video
/
SciShow
/
These Petroglyphs Helped Humans Survive the Desert
These Petroglyphs Helped Humans Survive the Desert
選擇學習模式:
查看字幕
選詞
重寫單字
Highlight:
3000 Oxford Words
4000 IELTS Words
5000 Oxford Words
3000 Common Words
1000 TOEIC Words
5000 TOEFL Words
字幕 (131)
0:00
Billboards are useful, at least if you want to know
0:02
whether you’re within two hundred miles of a Buc-ee’s.
0:04
Thousands of years ago, some people had a similar idea
0:07
by carving a huge camel into a rock in the Arabian peninsula.
0:12
That camel wasn’t signaling the location of gas and novelty foods,
0:16
but rather, something even more important: water.
0:19
Today, that camel is still conveying a surprising amount of information.
0:23
Not only has it doubled the amount of time
0:25
we think humans were living in the region…
0:27
it might also help crack a prehistoric climate mystery.
0:32
[♪INTRO]
0:34
The timeline of human habitation on the giant peninsula
0:38
southeast of the Fertile Crescent is long, but it’s not continuous.
0:42
Arabia has always experienced wetter and drier periods,
0:45
and there's evidence that humans have been
0:47
taking advantage of the grasslands these wet periods
0:50
provide for hundreds of thousands of years.
0:52
But the dry periods have rendered it pretty inhospitable.
0:55
For instance, during the Last Glacial Maximum
0:58
25,000 to 20,000 years ago, the entire globe got colder and drier.
1:04
Conditions in Arabia became pretty intolerable for prehistoric people.
1:07
When things got chilly and dry, humans skedaddled
1:10
out of there for at least five thousand years.
1:12
But eventually the glaciers around the globe receded,
1:15
and humans moseyed back in when Arabia became a bit balmier.
1:19
It's just that it’s difficult for scientists to pinpoint
1:22
when exactly this moseying took place.
1:24
Enter the life-sized camel murals, or petroglyphs.
1:28
And keep in mind that camels are big,
1:29
so these scale engravings are pretty striking.
1:32
And it’s not just camels these people were splashing across to cliffs.
1:35
They carved other stuff like ibex, wild donkeys and aurochs –
1:39
the extinct ancestors of modern cows.
1:41
The camels truly are impressive, though.
1:44
They can even be identified as males during the breeding season,
1:48
sporting furry coats only seen in the wet wintertime
1:51
when it’s time to make more camels.
1:54
One hundred and thirty of these naturalistic animal
1:56
engravings were found at three sites around Saudi Arabia,
1:59
including 18 in the Sahout area south of Saudi Arabia’s Nefud desert.
2:04
These animals marked important desert water sources,
2:07
and if we could date them, they might even solve the question of
2:10
when Arabia became habitable to humans and animals
2:13
again after the climate temporarily rendered it a wasteland.
2:16
The thing is, it's really tricky to determine the age of a rock carving.
2:20
Radiocarbon dating is a great way to tell the age of a very old
2:24
thing because carbon is present in all living things,
2:27
and it begins to decay at a predictable rate once the thing dies.
2:31
But you can’t really date geological formations that way,
2:34
because nothing's formerly alive.
2:37
Previously, researchers dated fireplaces to estimate human
2:41
habitation in the region went back about 7000 years,
2:44
but they admitted that was a very rough estimate.
2:47
But before we get to how old the site actually is,
2:50
here’s a quick break.
2:52
This SciShow video is supported by JMP:
2:54
the statistical analysis software trusted by nonprofits.
2:58
And we’re big fans of nonprofits here at Complexly.
3:02
Like WildTrack, a nonprofit that’s transforming wildlife
3:05
conservation. Instead of disturbing endangered species,
3:08
WildTrack uses footprints to protect them —
3:11
and then analyzes that data using JMP.
3:14
And you can be part of it! WildTrack relies on
3:17
hikers to share images of animal footprints.
3:20
Link in the description to get involved.
3:22
Since wildlife tracking requires you to go wherever animals are,
3:26
scientists use JMP across many countries
3:29
as their all-in-one software solution.
3:32
JMP helps the people at WildTrack understand complex
3:34
relationships, dig deeper, and uncover unexpected discoveries,
3:39
with their linked analyses and graphics.
3:41
To reap the benefits of visual statistics for yourself
3:44
and get a 30-day free trial, visit jmp.com/scishow.
3:51
In a 2025 paper, the same research team dated
3:54
the carvings themselves and almost doubled that figure.
3:58
They found a little tool similar to those found at petroglyph sites
4:02
around the world, from Europe to South America.
4:04
This engraving tool, called a pecking tool,
4:07
was found directly beneath an engraving of two giant camels.
4:11
Through a different technique called luminescence dating,
4:14
the tool was determined to be used around 12,000 years ago.
4:17
Luminescence dating works differently from radiocarbon techniques
4:21
because it measures the energy built up since
4:23
the last time crystalline minerals like silica,
4:26
found in quartz or feldspar rock, were exposed to sunlight.
4:30
The process can tell researchers when that particular
4:33
layer of sediment was last exposed to sunlight.
4:36
Of course, this tells us more about the layer of sediment
4:39
the pecking tool was found in than anything,
4:42
but that layer did include other trappings of human habitation,
4:46
like arrowheads and beads made of stone and shell.
4:49
And if you find rock art and also a tool used to make rock art,
4:52
it’s more likely than not that those two things go together.
4:56
Somebody was there -- most likely making
4:58
rock art and wearing fabulous jewelry.
5:00
So, what does the discovery of these camel billboards
5:03
tell us about what was going on in prehistoric Arabia?
5:07
Well, a few things:
5:08
For starters, it reinforces something researchers
5:10
already had an inkling about: that Arabia became warmer
5:14
and wetter after the last ice age, grasslands emerged
5:17
on the peninsula, and that attracted animals and people.
5:20
Environmental conditions were likely still pretty harsh, so these murals
5:24
were carved into cliff faces to mark important surface water sources.
5:28
However, this research suggests that surface water sources,
5:31
called playas, returned to the peninsula much sooner after
5:35
the last glacial maximum than previously assumed.
5:38
And of course, where there is water, there will be animals.
5:41
But the figures of camels in their wet season coats carved
5:44
into the rock, as well as the very presence of the aurochs,
5:47
give clues as to exactly how wet it was.
5:50
Aurochs, like modern cows, were thirsty,
5:53
so they'd need year-round access to water.
5:55
It’s possible that this site got wet enough that aurochs
5:58
would have been okey-dokey during the wet season.
6:01
But it’s also possible these murals were
6:02
made by folks who migrated seasonally.
6:05
They could have carved aurochs they had
6:07
seen on their journeys to wetter climes.
6:09
Either way, it's an important clue as to how
6:12
much water was available in the region.
6:14
All because people carved really accurate-looking animals!
6:17
Regardless, these rock art billboards seem
6:19
to mark the presence of these watering spots,
6:22
suggesting people followed a prehistoric superhighway of
6:25
ephemeral lakes, marking the route with these animal jumbotrons.
6:29
Now that researchers know what to look for,
6:31
maybe they can use the carvings to look
6:33
for more ancient water sources.
6:35
Or use more ancient art to learn more about our prehistoric climate.
6:43
[♪OUTRO]
