This episode introduces the geography of Sundaland in Southeast Asia,
linked to Landbridge during the Ice Age and the Early Human Migration associated with it.
When the last ice age reached its maximum,
there were substantial ice sheets in Europe and North America.
As much as 48 million km3 of water was in ice,
so the sea level was 120 meters (394 ft) lower than it is now.
This resulted in the formation of land bridges in several places
—Dogerland in Europe and now Beringia in the Bering Strait.
The ice age geography of these two regions was introduced in the previous video.
Even in Asia during this time,
there were areas where land bridges connected islands.
This is Sundaland, which was in Southeast Asia.
In this video, I will introduce the Geography of Ice Age Sundaland and the migration of modern humans to Asia.
During the LGM, the Last Glacial Maximum,
Sumatra, Java, and Kalimantan or Borneo in Indonesia were connected by a landbridge.
The Malay Peninsula and the Indochina Peninsula,
which includes Vietnam, Laos, Cambodia, and Thailand, are also joined by land.
The Philippine Islands of Palawan were landlocked with Borneo,
only about 25 km (14.5 miles) across Mindanao, Philippines.
The islands of the Philippines were also mostly landlocked.
The distance between Palawan and Mindoro, connected to Borneo, was only 55 km (33.5 mi).
Let's move a little north.
Let's move a little north. Hainan Island in southern China and Taiwan were also connected by land.
Also, the Yellow Sea between China's east coast and the Korean Peninsula's west coast became land.
The distance between Korea and Japan was less than 55km (34 mi).
The East Sea between Korea and Japan was left as a vast sea lake with only a narrow passage to the south.
Would you like us to go south of Sundaland?
A paleocontinent called Sahul included today Australia,
Tasmania, New Guinea, and the Aru Islands.
The area where Sundaland was 20,000 years before the present exactly matches where the ASEAN countries are today.
ASEAN comprises ten countries: Indonesia, Malaysia, the Philippines, and Vietnam and others.
This is a geopolitically important place.
The lost Sundaland was a paleo-network center associated with human migration.
Even today, the sea where Sundaland was located plays a vital role in world trade.
The volume of work that passes through this sea reaches 3.5 trillion dollars.
30% of world trade goes through the sea where Sundaland used to be.
Two-thirds of China's maritime trade passes through this sea,
and 40% of trade both of Korea and Japan passes through the sea where Sundaland used to be.
About 15 million barrels of crude oil pass through it daily,
about the same amount that passes through the Strait of Hormuz in a day.
The Strait of Malacca is a trade chokepoint of East Asian countries such as China, Japan, Korea, and Taiwan.
Even during the ice age 20,000 years ago,
this place was an important place where many people came and went as it is now.
Now, I will briefly introduce the ecological environment of this place.
Asian tigers and proboscis monkeys inhabit the western part of Bali.
The orangutan is a mammal only on the islands west of Bali.
From Lombok Island, east of Bali,
a completely different ecosystem exists.
Due to the year-round humid climate,
Lombok Island is blessed with giant tree forests.
The terrestrial fauna here is strikingly diverse from Bali's.
Tree tops once occupied by primates in Treetops, once occupied by primates in Bali, are inhabited by birds endemic to Australia in Lombok.
Curiously, the eastern islands of Bali have more Australian parrots than Indonesian species.
That's not all that's surprising.
Cassowaries, which have been passed down from the age of the dinosaurs, also live there.
It is a bird that has been isolated for a long time and cannot fly because its wings have degenerated.
This bird is also endemic to Australia.
Australia's representative species, the kangaroo,
can't be found west of the Wallace Line but in abundance in the east.
In 1895, the famous British natural scientist Alfred Russel Wallace discovered this and drew the distribution line.
That is the Wallace Line, which separates the biodistribution of Southeast Asia and Australia.
It was confirmed that terrestrial animals endemic to Southeast Asia were distributed west of Wallace's Line,
and Australian species were distributed east.
The Indonesian islands east of Wallace's Line are home to species not found elsewhere in Asia
—one of the giant reptiles on earth, the Komodo dragon.
Sulawesi's smallest monkey is the tarsier,
a species not found west of Wallace's Line.
Why do different ecosystems exist east and west of the Wallace Line?
At the end of the Miocene, the Indian and Asian continents collided slightly,
resulting in topographical changes.
At this time, some of Australia's terrestrial animals migrated to Indonesia,
forming the unique terrestrial ecosystem of the Wallace Line.
A scholar named Huxley even modified this line by extending it to the Philippines.
Since then, Max Wilhelm Carl Weber has proposed Weber's line to classify Australian mammal fauna as an alternative to Wallace's Line.
Weber's line offers the Tanibar island group, rather than Bali and Lombok,
as the boundary separating Southeast Asian species from those endemic to Australia.
There was the only mammal on Earth that crossed Wallace's line and Weber's line.
It was us, humans.
When did modern humans cross Wallace's line into Australia?
The earliest date of human occupation of Australia is given from sites in the Northern Territory.
The ruins of the Madjedbebe rock shelter in Arnhem Land are estimated to be about 50,000 years old.
In a paper published in Nature in 2017,
the claim that it dates back to 65,000 years was refuted by Allen & O'Connell in 2020.
Molecular clock estimates, genetic studies, and archaeological data
all place the first colonization of Sahul and Australia by modern humans at 48,000-50,000 years ago.
The area where they stayed before moving to Australia was Sundaland.
Homo erectus has been living here for at least 1.5 million years.
The first colonization of Sundaland by modern humans dates back 70,000 years ago.
Other species include the Denisovans.
And little by little, interbreeding with modern humans took place.
Melanesians and Aboriginal Australians have 3-5% of Denisovan DNA.
This suggests that modern humans who interbred with the East Eurasian Denisovans migrated to Australia and Papua New Guinea.
For the Denisova migration route information,
see the link "Denny with a Neanderthal mother and a Denisovan father."
The last Glacial peak was 20000 years ago.
It is also 120 m (394 ft) lower at sea level.
The LGM began around 33,000 years before the present.
Between 45,000 and 30,000 years ago,
glaciers in the Northern Hemisphere did not develop much.
45,000 years ago,
Europe was almost ice-free,
and the Laurentide ice sheet in North America was only 1/3 of the LGM.
If so, the migration time of humanity does not coincide with the time when Landbridge was in Sundaland, which we generally know.
So, did modern humans who migrated to Australia not use Landbridge?
There was another time when the northern hemisphere ice sheets grew to a similar extent to the LGM.
Between 58,000 and 72,000 years ago.
It almost coincides with the Toba Lake eruption.
For information on the Quaternary Glaciation,
see the linked "Ice Age: Quaternary glaciation and Habitats of Hominin."
The time when modern humans migrated to Australia and Sahul would have had a coastline similar to the LGM.
From now, I will introduce the Sundaland Vegetation of the LGM period,
58,000-72,000 years or 20,000 years ago.
Scientists claim that traits for modern dipterocarp trees in the Southeast Asian tropical rainforest have existed since the LGM.
Some Scientists suggest that a Savana Corridor existed on the Landbridge.
Vegetation models using climate simulation data suggest that the Savana corridor ran down the Malay Peninsula through Sumatra and Java to Borneo.
In addition, tropical Rain forests and Monson or Dry Forests existed around the Savana Corridor.
Before Sundaland emerged during the late Pliocene and early Pleistocene
(~2.4 million years ago), no mammals were on Java.
However, as the sea level lowered,
species such as the dwarf elephantoid Sinomastodon bumiajuensis colonized Sundaland from mainland Asia.
Later fauna included tigers, Sumatran rhinoceros, and Indian elephants found throughout Sundaland;
smaller animals could also disperse across the region.
The paternal DNA of the first Homo Sapiens arriving in Sundaland would have been haplogroup C.
This is because it is likely that modern humans who first set foot in Australia are 50,000 years old.
Paternal DNA present in indigenous peoples of Australia and Papua New Guinea are subclades of K2b1.
It is estimated that K2b1 was born 44300 years ago.
The most likely period for the formation of K-M9, the common ancestor of K2b1,
was also only 47200 years ago.
These are the subclades belonging to the other paternal DNA C1b possessed by Australia's Aborigines.
The earliest formation of C1b was about 47300 years ago,
and the common ancestor C would have first formed in western Asia around 65900.
Y-DNA Haplogroup C and their descendants first set foot in Sundaland.
And they would have lived in Sundaland during the Ice Age
between 58,000 and 72,000 years ago.
One of the sub-branches of C1b-F1370, and C1b1a-B65,
lived in Sundaland and migrated to the Philippines via Borneo.
Of the blanch of C1b2-B477,
M38 migrated to Papua New Guinea, and M347 migrated to Australia.
Migration from Asia to Sahul has two hypotheses.
The shortest route is to use the land bridge that appeared during the low sea level.
And some of these groups may have reached Arnhem Land in Australia's Northern Territory
by using the island as a stepping stone from Bali.
In this case, it was only 90 km from Timor to the Coast of Sahul.
Another hypothesis is that migration would have occurred when sea levels were high.
Rising sea levels in Sundaland may have increased population pressure.
They may have had to expand into new territories during this time.
The settlement of Australia by modern humans is indisputable evidence of humanity's first sea crossing
and ranks among humanity's most significant achievements.
Scientific reports in 2019 say, "Early human settlement of Sahul was not an accident."
According to the findings of this study, it was an intentional migration.
This supports the hypothesis of sea-level rising period migration.
This paper presents two migration routes,
assuming is 85-75 meters below sea level.
One route is the northern route via Sulawesi to New Guinea.
The other route is the southern route via Bali and Timor to the extended continental shelf of northwest Australia.
Reaching Sahul required an open ocean crossing of at least 100 km
and several short 20-30 km crossings.
Modern humans would take a few thousand years to pass through Wallacea.
Human migrations may have occurred during the LGM and post-LGM sea level re-rising.
The population that migrated during this time belonged to the blanch of Y-DNA K2b.
K, who had the Y-DNA haplogroup IJK as his direct ancestor,
may have migrated to Sundaland from West Asia.
Among the branches of K-M9,
LT migrated to West Asia, Africa, the Middle East, and the Aegean Islands,
and the most likely region for the formation of K2-M526 was South or Southeast Asia 45300 years ago.
However, it is more likely that it was Sundaland.
This is where K2a-M2308 and K2b-P331 may have emerged.
K2a, the direct ancestor of Y-DNA N and O,
migrated to East Asia and constituted the major paternal DNA of East Asians.
Of these, N moved to Northern Europe via Siberia.
K2b-P331 lived in Sundaland,
and Blanchs belonging to K2b1 migrated to Australia and Papua New Guinea.
K2b2, also known as Y-DNA P, migrates near Baikal.
And it gave rise to the R, which makes up the modern European Y-DNA,
and the Y-DNA Q, which makes up Native Americans.
For more information on their migration routes,
please see the videos on R's and Q's migration routes on the GeoNomad channel.
So far, we have introduced the geopolitical importance of modern Southeast Asia and Paleo-Southeast Asia,
the geography of Sundaland, which was Paleo-Southeast Asia,
and the migration route of modern humans via this place.
Lastly, I will show the process of Sundaland closing each year due to sea level rise through a map.
Thank you for watching until the end.
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