Study claims to identify the homeland of all modern humans

A DNA study looks for the home of the earliest modern humans.

Study claims to identify the homeland of all modern humans

Okavango Delta.

Credit: Justin Hall/Wikimedia
  • A DNA study traces the homeland of modern humans to the Makgadikgadi-Okavango wetland.
  • The area is shared by the modern-day countries of Botswana, Namibia and Zimbabwe.
  • The researchers drew conclusions from the mitochondrial DNA of humans living in that area today, but some scientists question their methodology.

Is there a specific location on Earth where humans like us originated? A new study pinpoints an area called the Makgadikgadi-Okavango wetland, shared by the modern-day countries of Botswana, Namibia and Zimbabwe in southern Africa as the birthplace of modern humans (Homo sapiens sapiens) about 200,000 years ago.

Scientists from the Garvan Institute of Medical Research discovered that the earliest ancestors of humans appeared in that area and lived there for about 70 thousand years. Eventually, they were forced to expand their domain by the climate changes in Africa.

The study lead Professor Vanessa Hayes from the Garvan Institute of Medical Research, who is also associated with the University of Sydney and the University of Pretoria, highlighted the significance of their find:

"It has been clear for some time that anatomically modern humans appeared in Africa roughly 200 thousand years ago," said Hayes. "What has been long debated is the exact location of this emergence and subsequent dispersal of our earliest ancestors."

For their study, the scientists focused on examining the mitochondrial DNA of modern-day residents of the area. Hayes explained that "Mitochondrial DNA acts like a time capsule of our ancestral mothers, accumulating changes slowly over generations." This fact allowed the researchers to compare the DNA code (or mitogenome) of different people to figure out how closely related they are.

The scientists were able to use collected blood samples to put together a much improved catalogue of the mitogenomes of early humans.

The study's first author Dr. Eva Chan from the Garvan Institute of Medical Research, who led the phylogenetic analyses, expanded on their methodology:

"We merged 198 new, rare mitogenomes to the current database of modern human's earliest known population, the L0 lineage," said Chan, adding "This allowed us to refine the evolutionary tree of our earliest ancestral branches better than ever before."

Dr Eva Chan & Professor Vanessa Hayes.

The researchers looked at the L0 lineage timeline in combination with distributions of various sublineages based on language, culture and geography. What they found is that the maternal lineage of humanity emerged in what they dubbed a "homeland' area south of the Greater Zambezi River Basin region. This "homeland" includes all of northern Botswana stretching into Namibia to the west and Zimbabwe to the east.

Why was this area so perfect for humans to develop? According to research by the geologist Andy Moore of Rhodes University, that area once contained Lake Makgadikgadi – Africa's largest-ever lake system. Once the lake started to drain due to shifts in the tectonic plates underneath, it left behind a fertile wetland, which was favorable for sustaining life.

The ecosystem was home to the early humans for 70K years until about 130 to 110 thousand years ago, when people started venturing out northeast and southwest from the area, while a group stayed in the area (with their descendants still found there today).

Why did many people leave the "homeland," which today is actually one of the largest salt flats in the world? Climate change simulations from the study's co-corresponding author Professor Axel Timmermann, Director of the IBS Center for Climate Physics at Pusan National University, point to shifts in rainfall which created "green, vegetated corridors" leading out of the area. These allowed the human ancestors to leave the homeland and look for greener pastures elsewhere.

"These first migrants left behind a homeland population," pointed out Professor Hayes. "Eventually adapting to the drying lands, maternal descendants of the homeland population can be found in the greater Kalahari region today."

Not everyone is on board with the scientists' findings. Mark Thomas, an evolutionary geneticist at the University College London, said in an email to National Geographic that "The inferences from the mtDNA data are fundamentally flawed." He also called the study "storytelling."

But others, like University of Hawaii at Manoa geneticist Rebecca Cann, who was a reviewer of the study and has carried out her own pioneering work on mitochondrial DNA, supports the study, saying while the study is "not perfect", it will move the science along and "stimulate a lot of new studies."

Check out the new study "Human origins in a southern African palaeo-wetland and first migrations" published in Nature.

A landslide is imminent and so is its tsunami

An open letter predicts that a massive wall of rock is about to plunge into Barry Arm Fjord in Alaska.

Image source: Christian Zimmerman/USGS/Big Think
Surprising Science
  • A remote area visited by tourists and cruises, and home to fishing villages, is about to be visited by a devastating tsunami.
  • A wall of rock exposed by a receding glacier is about crash into the waters below.
  • Glaciers hold such areas together — and when they're gone, bad stuff can be left behind.

The Barry Glacier gives its name to Alaska's Barry Arm Fjord, and a new open letter forecasts trouble ahead.

Thanks to global warming, the glacier has been retreating, so far removing two-thirds of its support for a steep mile-long slope, or scarp, containing perhaps 500 million cubic meters of material. (Think the Hoover Dam times several hundred.) The slope has been moving slowly since 1957, but scientists say it's become an avalanche waiting to happen, maybe within the next year, and likely within 20. When it does come crashing down into the fjord, it could set in motion a frightening tsunami overwhelming the fjord's normally peaceful waters .

"It could happen anytime, but the risk just goes way up as this glacier recedes," says hydrologist Anna Liljedahl of Woods Hole, one of the signatories to the letter.

The Barry Arm Fjord

Camping on the fjord's Black Sand Beach

Image source: Matt Zimmerman

The Barry Arm Fjord is a stretch of water between the Harriman Fjord and the Port Wills Fjord, located at the northwest corner of the well-known Prince William Sound. It's a beautiful area, home to a few hundred people supporting the local fishing industry, and it's also a popular destination for tourists — its Black Sand Beach is one of Alaska's most scenic — and cruise ships.

Not Alaska’s first watery rodeo, but likely the biggest

Image source:

There have been at least two similar events in the state's recent history, though not on such a massive scale. On July 9, 1958, an earthquake nearby caused 40 million cubic yards of rock to suddenly slide 2,000 feet down into Lituya Bay, producing a tsunami whose peak waves reportedly reached 1,720 feet in height. By the time the wall of water reached the mouth of the bay, it was still 75 feet high. At Taan Fjord in 2015, a landslide caused a tsunami that crested at 600 feet. Both of these events thankfully occurred in sparsely populated areas, so few fatalities occurred.

The Barry Arm event will be larger than either of these by far.

"This is an enormous slope — the mass that could fail weighs over a billion tonnes," said geologist Dave Petley, speaking to Earther. "The internal structure of that rock mass, which will determine whether it collapses, is very complex. At the moment we don't know enough about it to be able to forecast its future behavior."

Outside of Alaska, on the west coast of Greenland, a landslide-produced tsunami towered 300 feet high, obliterating a fishing village in its path.

What the letter predicts for Barry Arm Fjord

Moving slowly at first...

Image source:

"The effects would be especially severe near where the landslide enters the water at the head of Barry Arm. Additionally, areas of shallow water, or low-lying land near the shore, would be in danger even further from the source. A minor failure may not produce significant impacts beyond the inner parts of the fiord, while a complete failure could be destructive throughout Barry Arm, Harriman Fiord, and parts of Port Wells. Our initial results show complex impacts further from the landslide than Barry Arm, with over 30 foot waves in some distant bays, including Whittier."

The discovery of the impeding landslide began with an observation by the sister of geologist Hig Higman of Ground Truth, an organization in Seldovia, Alaska. Artist Valisa Higman was vacationing in the area and sent her brother some photos of worrying fractures she noticed in the slope, taken while she was on a boat cruising the fjord.

Higman confirmed his sister's hunch via available satellite imagery and, digging deeper, found that between 2009 and 2015 the slope had moved 600 feet downhill, leaving a prominent scar.

Ohio State's Chunli Dai unearthed a connection between the movement and the receding of the Barry Glacier. Comparison of the Barry Arm slope with other similar areas, combined with computer modeling of the possible resulting tsunamis, led to the publication of the group's letter.

While the full group of signatories from 14 organizations and institutions has only been working on the situation for a month, the implications were immediately clear. The signers include experts from Ohio State University, the University of Southern California, and the Anchorage and Fairbanks campuses of the University of Alaska.

Once informed of the open letter's contents, the Alaska's Department of Natural Resources immediately released a warning that "an increasingly likely landslide could generate a wave with devastating effects on fishermen and recreationalists."

How do you prepare for something like this?

Image source:

The obvious question is what can be done to prepare for the landslide and tsunami? For one thing, there's more to understand about the upcoming event, and the researchers lay out their plan in the letter:

"To inform and refine hazard mitigation efforts, we would like to pursue several lines of investigation: Detect changes in the slope that might forewarn of a landslide, better understand what could trigger a landslide, and refine tsunami model projections. By mapping the landslide and nearby terrain, both above and below sea level, we can more accurately determine the basic physical dimensions of the landslide. This can be paired with GPS and seismic measurements made over time to see how the slope responds to changes in the glacier and to events like rainstorms and earthquakes. Field and satellite data can support near-real time hazard monitoring, while computer models of landslide and tsunami scenarios can help identify specific places that are most at risk."

In the letter, the authors reached out to those living in and visiting the area, asking, "What specific questions are most important to you?" and "What could be done to reduce the danger to people who want to visit or work in Barry Arm?" They also invited locals to let them know about any changes, including even small rock-falls and landslides.

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