In once-lush wetlands some 200,000 years ago, it is believed that the species Homo sapiens originated. Considered to be modern-day humans, Homo sapiens evolved from their Neanderthal ancestors and the reign of humans began. Scientists have just recently pinpointed the place where most humans likely originated. Geneticist Vanessa Hayes of the Garvan Institute of Medical Research in Sydney conducted research using DNA samples as a way to find just where humans may have come from. Mitochondrial DNA is a material that's passed from mother to child that may allow researchers like Hayes to find a maternal line that reaches far into the past. They may have found the answer to one of humankind's greatest questions.
An Ancient Lake
After the DNA samples were taken and analyzed, further archaeological and geological research helped Hayes discover something incredible. She stumbled upon evidence of a large, ancient lake that eventually developed into wetlands. It is this place that some experts believe was the home of the first humans.
For years, researchers have proposed that humankind can be traced back to the continent of Africa. This was over seven million years ago when humans began to evolve from primates.
There Are Still Missing Pieces In The Evolutionary Chain
Although it's virtually impossible to find every link between humans and primates, an entire species can't have come and gone without ever leaving a trace for researchers to find. This is why we only have partial pieces of information about our evolution to work with.
The secret to humankind's ancestral roots becomes more evident as scientists move closer to present-day. For example, we now know that Neanderthals roamed Europe and even moved into Siberia and Central Asia. However, Neanderthals may not have directly given way to Homo sapiens.
Humans' Early Descendants
Instead of Neanderthals, it's likely that the evolution of Homo heidelbergensis and the Homo erectus gave way to Homo sapiens. These new humans had a variety of differences that separated them from the Neanderthals who walked the world before them.
For example, Homo sapiens were far more slender than the thicker Neanderthals that lived farther north. Additionally, Homo sapiens mastered the art of making and working with tools in a way that Neanderthals never did.
Similar Lifestyles
Because both Homo sapiens and Neanderthal populations had similar lifestyles, experts were confused. It led scientists to develop two hypotheses about where mankind evolved.
The first is the multi-regional hypothesis, which suggests that human ancestors spread across the globe. This resulted in Homo sapiens evolving at the same time, although in different places. The other is the Out-Of-Africa theory, which claims that modern humans evolved on the continent of Africa before migrating across the globe. Since the 1980s, this is considered to be the theory with the most evidence.
It Comes Down To DNA
The reason that the Out-Of-Africa theory was able to gain so much traction is because of DNA. Through DNA testing, scientists were able to analyze the genetic information of the modern population and trace it back to see where their ancestors may have come from. DNA researchers were then able to trace multiple test subjects' lineages to one place of origin, which almost always seemed to be Africa.
In the original studies, mitochondrial DNA was used, which is part of the genetic code that comes from mothers. This DNA tends to have more mutations and therefore, it is easier to follow how variations have developed from mothers to children for generations.
Introducing "Eve"
By tracing mitochondrial DNA back to the cradle of civilization, it's been discovered that one woman's genetic code has been carried through everyone on Earth today. She's referred to by scientists as "Eve," although she is not the biblical figure and not the first woman on Earth.
Eve lived during a time when the entire human population was just around 10,000. During her life, she managed to give birth to an unbroken line of daughters who passed her mitochondrial DNA throughout the ages and into present day.
The Most Recent Common Ancestor
According to Smithsonian magazine, Eve is considered to be humankind's "most common ancestor." Furthermore, in 2008, a DNA study confirmed that Eve is the only woman of her time to have an unbroken lineage of daughters and that she had originated in Africa.
Eve's DNA is considered to be the start of modern humankind's story. However, other questions remained, such as how early humans spread to different continents and why there were an unusual amount of fossils found in Europe.
Moving Out Of Africa
The information discovered showed that the major migrations of early Homo sapiens began between 60,000 and 80,000 years ago. Around this time it's believed that humans left their African origins for Asia. From 45,000 years ago, they seemingly made it to Australia, Indonesia, and Papua New Guinea.
About 5,000 years after that, they began to make their way to Europe. It is likely that those who went from Africa to Europe took one of two routes north. Some would take the Mediterranean coast while others may have passed through Turkey along the Danube. This migration pushed the Neanderthals out of their homes until they disappeared altogether around 25,000 years ago.
Reaching The Americas Was The Final Step
Eventually, mankind's journey would bring them to the Americas around 15,000 years ago. The trek started in Asia and crossed the Pacific to reach North America, and then eventually what is now South America.
Incredibly, the majority of this information comes from the fossils of the first humans to make these amazing journeys across the globe. Over thousands of years, the landscape of Africa has greatly changed as well, with the vast dry landscapes revealing the bones of our early ancestors.
Early Homo Sapiens Remains Are Rare
Even though researchers have been able to answer many questions by studying the bones of our ancestors, there aren't many remains found, whether looking in Africa or Europe. That has led experts to assume that these early humans didn't bury their dead like Neanderthals, but cremated them or left them to decompose.
Despite the lack of human fossils, science has aided in answering many questions about early human origins. In 2019, a study performed by Vanessa Hayes of the Garvan Institute once again brought about the discussion of mitochondrial DNA.
Hayes Was Thorough In Her Research
In total, Hayes and her team gathered 1,217 mitochondrial DNA samples from individuals that were currently living in South Africa. Some of the subjects came from the Khoisan population, an indigenous people whose way of life hasn't changed in generations.
From those samples, Hayes and her team were able to trace what is known as the L0 lineage in the subjects' mitochondrial DNA. The L0 lineage goes back to Eve, whose original DNA was split into five main branches as people left Africa and scattered across the globe.
The L0 Line Changed As People Migrated
The L0 line has its own variations, as it branched off about 130,000 years ago when some human populations traveled elsewhere after the lands began to dry up. While some moved south to follow the greenery, others moved northeast to become foragers or farmers.
Of course, the L0 mitochondrial DNA had to have started somewhere, and Hayes and her team were able to find out exactly where that was. They found that L0 and all of its sub-branches also traced back to Africa.
The Team Went Deeper Than DNA
However, Hayes didn't just rely just on her DNA findings to try and seek out answers about the past. The team also included archaeological, geological, and fossil evidence in their research.
Their results showed them that although many locations of interest seem uninhabitable during current times, the discoveries regarding human origins show that the area once looked very different. In fact, the landscape looked so different 200,000 years ago that few people could fathom the major changes.
There Was Once A Lake
It's believed that there was a massive lake, known as Lake Makgadikgadi, that was roughly the size of New Zealand. When the lake was still in existence, it is thought to have covered a large area of what is now Botswana.
Around 200,000 years ago, the lake transformed into a wetland, which Hayes and her team believe was the cradle of modern humankind. It would have provided the perfect location for early humans to flourish before setting off across the globe.
The Landscape Has Completely Transformed
Considering how arid the region is today, it's hard to believe that it could have possibly sustained the beginnings of human life. The former wetland is located south of the Zambezi River and is now dry with large salt flats scattered throughout.
According to Hayes, however, 200,000 years ago, these current unforgiving salt pans were full of water and resources necessary for life. In 2019, she told The Guardian, "It would have been very lush, and it would have provided a suitable habitat for modern humans and wildlife to have lived."
Climate Changed The Landscape
Hayes went on to add that the Botswana-situated wetland would have been a kind of oasis to the surrounding arid landscape. She claims that although early humans may have originated there over 200,000 years ago, they remained there for 70,000 more years.
A shift in climate drove them from the area. New lands began to develop in the surrounding areas that gave our ancient ancestors the possibility of moving out from the wetlands and into new territory.
The Earth's Orbit Played A Role
As the Earth's orbit and tilt shifted, it provided new rains to different areas of Africa, creating lush corridors. These green pathways allowed early humans to branch out into new territories.
Prior to this shift in climate and the tilt of the Earth, early humans were essentially stranded, as the surrounding land was arid and dry, and they were residing in one of the few hospitable places. This was a precursor to the great global migration.
Discovering The Exact Location
Although Hayes and her team were sure that human origins can be traced back to Africa, they finally believed they knew exactly where.
She stated, "We have known for a long time that modern humans originated in Africa and roughly 200,000 years ago, but what we hadn't known until this study was where exactly." They believe that place is the wetland in Botswana.
Those That Doubted Didn't Think DNA Held All The Answers
Among those who disagreed with Hayes' claims is Chris Stringer, an expert in human origins at London's Natural History Museum. He believes that modern-day DNA samples might not be entirely representative of the past.
He notes, "I'm definitely cautious about using modern genetic distributions to infer exactly where ancestral populations were living 200,000 years ago – particularly in a continent as large and complex as Africa."
Mitochondrial DNA Might Not Have Been The Answer
Stringer also believed that Hayes and her team had been too reliant on the information that they discovered when researching mitochondrial DNA and the L0 lineage, which was the basis of much of their research.
Stinger went on to warn, "Like so many studies that concentrate on one small bit of the genome, or one region, or one stone tool industry, or one 'critical' fossil, it cannot capture the full complexity of our mosaic origins once other data [is] considered."
Stringer Believed Humans Emerged In Other Places In Africa
Although Hayes may have some convincing points, additional studies have also traced humankind's ancestors to other locations on the African continent. Stringer discusses research that focuses on the Y chromosomes that only men inherit, very different than basing studies on Eve only.
This chromosomal research suggests that the great migration that occurred did not begin where Hayes has indicated, but from West Africa, which is quite a way from landlocked Botswana in the south.
Other Possibilities
On top of Hayes' and the Y chromosome theories, other possibilities have emerged in relation to where humans originated. One study found that those who left Africa carried specific genomes that could be traced back to Africa's eastern areas.
Stringer commented on this theory. "These and many other data suggest that we are an amalgam of ancestry from different regions of Africa with, of course, the addition of interbreeding from other human groups outside the continent," he said.
More Than Just DNA
In the end, Stringer refers to Hayes' finding as an "over-reach." He explained to BBC News.
"You can't use modern mitochondrial distributions on their own to reconstruct a single location for modern human origins," he said. "I think it’s over-reaching the data because you’re only looking at one tiny part of the genome, so it cannot give you the whole story of our origins." He believes that to find a solid answer, many different factors need to be taken into consideration.
More Than One Place
There are also those who believe that humankind came from more than just one place -- actually, several at the same time. Rebecca Ackermann, an archaeologist at the University of Capetown, expanded on this theory.
She told The Guardian that she believes humans may have originated in Africa and other places. She said, "Drawing sweeping conclusions about places of origin from analyses of this tiny part of the modern genome is deeply problematic and outdated."
Hayes Is Convinced About Her Theory
Regardless of the many other theories, Hayes' study did provide evidence for a possible pinpoint as to exactly where humans originated. Despite her use of science to study the DNA of living people and trace it back to common ancestors, many still believe there is no definitive answer.
For the time being, it's not out of the question to consider that 200,000 years ago, the first early humans emerged from the Botswana wetlands.
