Scientists have recently uncovered evidence that the origins of Homo sapiens might be more varied and complex than we ever imagined. You see, a team of researchers from the University of California, Los Angeles (UCLA) have discovered a mysterious ghost population that has been lurking, unseen, in our lineage for hundreds of thousands of years. And this group of previously unheard-of ancestors has left a startling legacy on all humans living today.
The eyebrow-raising findings were first published in Science Advances in February 2020. As part of the study, researchers from UCLA did work on DNA taken from West Africans. The group then compared this with the genomes of Neanderthals and Denisovans. Their idea was that if the genomes shared variations, this would indicate that our ancestors had mixed with other populations before leaving Africa and expanding across the globe. And the results were stunning: a ghost population emerged.
What does this mean? Well, it’s important to view the study in context. As the researchers wrote, “While several studies have revealed contributions from deep lineages to the ancestry of present-day Africans, the nature of these contributions remains poorly understood.” This is partly due to DNA being hard to come by from Africa’s scarce fossils. This, then, is what we know for sure so far.
Human beings began in Africa about 300 millennia before the present day. It’s thought that Homo sapiens evolved in a period of climatic upheaval, too. They weren’t the only human species that existed at the time, either. But like the others, Homo sapiens were hunter-gatherers who needed to adapt to difficult environments.
There were some noticeable differences between Homo sapiens and the other human species, though. One of these is that they were more lightly built. They also boasted big brains. And accommodating these brains led to their skull shapes looking the way modern humans’ craniums do today. Yes, we have ancient Homo sapiens to thank for our less prominent brows and our jaws not jutting out so much.
Nowadays, of course, various species of humans that once comprised the other parts of the genus Homo are long extinct. But we can see from fossils that there were many different hominins – the name for species that are similar to us. We also know that Homo sapiens lived at the same time as at least one other human species: Homo neanderthalensis, or the Neanderthals.
Humans have lived alongside other primates, too. If you had a time machine, for instance, you’d be able to observe our ancestors in African environments with ape-like animals such as Dryopithecus. That said, it doesn’t strictly make sense to state that humans descended from the apes – only that humans and apes share common ancestors.
Why’s that? Well, in theory, you could trace our lineage back far enough and find an ancestor of both us and existing apes. But scientists cannot say for sure which animal that might have been – as even the more recent relationships between human ancestors are not entirely clear. In fact, experts may never agree on exactly how we are related to our ancestors – or even which primates they are.
That said, scientists do agree about the broader outlines of the progression of human evolution. One thing that seems clear is, for instance, that the ancestors of humans emerged at some point more than 5 million – but less than 7 million – years before the present. This is when creatures rather like apes began to walk upright rather than on all fours.
These ancestors probably evolved from Australopithecus afarensis, which is renowned for providing the fossil named “Lucy.” This 3.2-million-year-old specimen was discovered in Ethiopia, and it’s older than any Homo designate. In fact, the next earliest fossil shows up nearby in the form of a 2.8-million-year-old jawbone. And fossils only become anywhere near common at the 2-million-year mark – when several species of Homo ancestors coexisted.
Fortunately, at about 2.5 million years before the present, these early humans were able to make tools – and this advance may have helped them survive a drying environment. Around 2 million years ago, you see, the change in climate might well have been responsible for some of these hominins spreading out of Africa.
Homo erectus led the way out of Africa, it seems. How do we know this? Well, its fossils – which are two millennia old – have been found in East Africa. Fossils dated around a couple of hundred thousand years later have also been found in what is now the far eastern European country of Georgia. Homo erectus then radiated into Asia, with the species thriving in Java, for instance, for more than a million years.
The spreading Homo erectus had a string of descendant species, too. One of which, Homo heidelbergensis, followed it out of Africa. It mostly went west, though, and it gave rise eventually to the Neanderthals. Yet the Homo heidelbergensis who remained behind eventually led to modern humans, while those in Asia led to the Denisovans – another similar species.
So about 130,000 years before now, the world had several species of hominins wandering around it. But that would eventually change, as Homo sapiens also left Africa. Homo sapiens would eventually push out the other hominins everywhere it went, too. This process took time, though, and – as we’ll see – it involved some intermixing of the species.
Interestingly, scientists have discovered from our genes that we all descend from humans that left Africa in a second wave about 60,000 years ago. So the first wave of Homo sapien settlers may not have stuck, as they got to the Middle East 100,000 years ago and China 20,000 years later. When the second wave hit, though, the migrants moved quickly to colonize most of the world. They reached the Americas around 16,000 years before the present.
Importantly, though, when these humans reached Europe, they would have encountered the Neanderthals. Although the latter went extinct around 40,000 years ago – remnants in Spain might have lasted a little longer – contact between the species wasn’t entirely hostile. On the contrary, geneticists confirm that there must have been some romance – because Neanderthal DNA combined with ours.
Yes, when in 2010 scientists sequenced the genome of a Neanderthal fossil from Croatia, it became clear that the species had mated. Researchers believe that the first contact was probably 60,000 years before the present in the Middle East. So now all humans – except for Africans – have up to a couple of percent of Neanderthal DNA.
In Asia, meanwhile, humans also mated with Denisovans – a little-known group of hominins. We can actually only say anything about the Denisovans because of the very few remains of them that have been discovered and the DNA that lay in them. Yet that DNA is reflected by up to 4 percent of the genes in modern indigenous Australians and the related Melanesian peoples.
So Denisovans might have been more widespread than their few remains would indicate. Fossils that are only about ten millennia old may also be Denisovans. These hominins got around, too. We know, for instance, that they interbred with Neanderthals and another old species that scientists think could be the hobbit-like Homo floresiensis.
Some Neanderthal DNA does turn up in Africans as well. This provides further evidence for the two-waves theory of human migration. The assumption is, then, that some of the original migrants of 200,000 years ago likely interbred with Neanderthals before returning to Africa. Before the discovery of Neanderthal ancestors by Princeton scientists in 2020, though, Africans had been thought not to have had any.
Of course, all this mixing of species excites some scientists. Richard “Bert” Roberts, a researcher from Australia’s University of Wollongong, told Cosmos magazine in 2018, “I’d have loved to have been on the planet 60,000 years ago. We used to have a fabulous time, with all sorts of other humans running around the planet.”
For hundreds of thousands of years, then, we intermingled with Neanderthals and Denisovans. But then the diversity of the past gave way to a world in which we’re the only hominins. However, Roberts views today’s less-diverse situation somewhat dismissively. He remarked, “What a boring state we’re now in with only one human species left on the planet.” The researcher added, “What a yawn!”
He might have a point. After all, Homo sapiens, Neanderthals and Denisovans were not the only species involved in the intermixing process – as research has recently uncovered. Scientists are even finding ever more evidence that “ghost populations” of extinct hominins contributed to the human story long before we left Africa. One candidate species for having mated with later modern humans is Homo erectus.
Finding ghost populations is not an easy task, though. It requires studying the human genome using complicated models of the intermixing of populations and inheritance. The outcomes are far from certain, too – particularly when we hope to point the finger at who the ghosts were. The mixing of them and modern humans is tricky to identify as well.
Yet the new evidence does make it clear that it wasn’t rare for the varied ancestors of humans to get together and get it on. Murray Cox, a computational biologist at Massey University (Turitea) told Science magazine in February 2020, “It’s now clear that interbreeding between different groups of humans goes all the way back.”
The way that interbreeding is identified with the highest degree of certainty is to sequence DNA that has been extracted from fossils. Then it can be compared with modern genomes to see whether any trace remains. This method revealed the intermingling with Neanderthals and Denisovans – but fossils older than them have not offered up their DNA.
It’s because of this that scientists working in genetics have developed mathematical tools to examine DNA from today’s humans. By using statistical methods, then, the researchers hope to identify past mixings of genes. And after a decade of maybes, they have honed in on two stretches of interbreeding from the extremely distant past.
A team working under population geneticist Alan Rogers, who operates out of The University of Utah, have found variations at the same place in different genomes. These genomes are from not just Europeans and Asians of today, but also Neanderthals and Denisovans. The team then looked at hypothetical outcomes from eight different mathematically modeled cases of mixing to figure out which one best matched what they could see. And the results were astonishing.
Rogers’ group discovered that the common precursors of the Neanderthals and Denisovans had mixed with another ancient population 2 million years before the present. The ghost population whose DNA was there to be seen in the “Neandersovan” genomes may have been Homo erectus. And if this is the case, the interbreeding probably happened outside Africa.
Rogers believes that he knows who the culprits are for the interbreeding that he found, though. He said, “I think the super-archaics were in the first wave of hominids who left Africa. They stayed in Eurasia, largely isolated from Africans, until 700,000 years ago when Neandersovans left Africa and interbred with them.”
This must have been a long time before modern humans left Africa. Rogers called it “the earliest known interbreeding between ancient human populations and an expansion out of Africa.” So it may be that the mixing happened both in Africa and outside of it – although not everyone agrees with that theory.
For instance, the UCLA scientists suggested that the mixing of species in Africa might be a better explanation for the variations of genomes that we see today. When these researchers looked at the West African genomes, you see, they discovered outcomes not seen in Neanderthals or Denisovans. This implies that ancient populations provided the genes after humans had left Africa for the second time.
Who these candidates might have been is still in question, though. It could even be a single Homo erectus, Homo heidelbergensis or other related species that survived long enough to mate with the dominant Homo sapiens within the most recent 124,000 years. Or it could be a mixture of all three. And although long gone, these hominins live on in Africans’ DNA.
For the UCLA researchers, though, the matter is complicated because Neanderthal DNA has been discovered in modern African genomes. The lead scientist on the UCLA team, Sriram Sankararaman, said a small portion of what he found might be explained by the back-migration of Neanderthals. But, he felt, it was most likely to have originated from the archaic ghost hominins.
The UCLA team is not the only one to have uncovered a ghost population in Africa, either. University of California San Francisco (UCSF) scientists found strong echoes in the Khoisan of southern Africa and pygmies of central Africa. But this team could not pinpoint what the ghost population or populations were or when the mixing had happened.
Geneticist Jeff Wall from the UCSF team had a warning, though. He explained that it might be that the ghost population was just other modern humans who had lived in separation from the other Homo sapiens for so long that they looked like a different, archaic species. Commenting on this, Princeton University’s Joshua Akey told Science, “Our understanding of African population history, in particular, is so far behind.”
Whatever the truth of who the ghost population of hominins are, though, one thing that the scientists agree on is that even hugely separate groups can intermix. Population geneticist Pontus Skoglund, who works at the Francis Crick Institute in London, told Science that this was confirmed by looking at other species that also mix with widely separated groups. He said, “We are losing the idea that separation between populations is simple with instant isolation.”
And the intermixture of groups that have been separated from one another for a long time can be very positive. It’s a good way to bring novel genes into a population, for one thing. This can have benefits when useful traits have evolved. Sankaraman found archaic variations in genes that control hormones and fight tumors, for instance.
Lacking the possibility of a big influx of diversity is not a good thing for modern humans, either. Now that we’re the only humans, you see, we cannot get a positive influx from other, closely related species. Uppsala University’s Carina Schlebusch told Science, “To have such a large densely-spread species with… so little genetic diversity… is a dangerous situation.”
Still, we may yet find more ghost populations. Bioarchaeologist Joel D. Irish from Liverpool John Moores University said to news network CNN in February 2020, “I think at one time, there’d have been all sorts of populations, with genetics different enough to look a bit different. Everybody tends to mate with everybody. I think we’re going to find more and more of these ‘ghost’ populations coming up.”
A ghost town has actually cropped up on America’s western coast. In 2015 the area was in the grip of a severe drought that was being felt far and wide. Over in Marion County, Oregon, for example, Detroit Lake was the lowest that it had ever been. And yet as the reservoir slowly dried up, the waters receded to reveal a stunning sight. Rising from the lake were the relics of an old railroad town – one that had been hidden from sight for over 60 years.
Located in the famously picturesque area of America known as the Pacific Northwest, Oregon is renowned for its magnificent landscapes. From the state’s golden, sandy beaches to the lush, green expanses of its parks, this is a place that delights millions of visitors every year.
Now, one of Western Oregon’s most popular attractions is Detroit Lake – a reservoir on the North Santiam River that lies near to the small city of Detroit in Marion County. At nine miles long, Detroit Lake boasts some 32 miles of shoreline. The water there also provides local residents with plenty of opportunities for fishing, swimming, boating and other recreational activities.
On top of this, Detroit Lake supplies water to neighboring communities – such as the city of Salem, which sits some 46 miles to the northwest. This state of affairs hasn’t always been the case, though. In fact, the body of water was only created in 1953, when a dam was built to control flooding in the nearby Willamette River.
And although Detroit Lake was constructed for practical reasons, it has since become arguably one of the region’s most valued recreational sites, with sunbathers and swimmers enjoying the cool waters on hot summer days. That said, as with similar bodies of water, the weather can greatly affect the reservoir. Factors such as rainfall and snowmelt can cause the water levels to change, for instance.
A lack of precipitation can drastically change the state of the reservoir too. You see, in 2011 Marion County – along with many of America’s western coastal states – began suffering from a terrible drought. So it was that by the start of the 2015 summer season, Detroit Lake was already some 60 feet below its normal capacity. Shockingly, over the coming weeks, the water level would then plunge by a further 83 feet.
At just 1,426 feet, the water was at its lowest point ever. Such a drastic drop had only been recorded once before, in January 1969. And even though the lake’s water level had previously fallen to 1,427 feet three further times, this record drop revealed something that the reservoir had kept hidden for generations.
Yes, in the fall of 2015, a startling sight confronted local residents. There, exposed on the lakebed, were the remains of Old Detroit – a remnant of times long since past. After all, the town had been abandoned and swallowed up when the North Santiam River was dammed back in 1953.
Founded in 1880, Old Detroit started life as a camp meant to house men working on the Oregon Pacific Railroad. This ambitious venture – the brainchild of local businessman Thomas Egenton Hogg – was originally intended to connect the state with the east of the country. Ultimately, though, it never quite reached its potential.
Beginning in the city of Salem – some 50 miles east of Old Detroit – the railroad once followed the path of the mighty North Santiam River. Then, after the track traversed the canyon floor, it reached the foothills of the Cascade Range of mountains. Hogg even planned to continue through the Cascades and onward towards the Transcontinental Railroad.
Sadly, though, Hogg ran out of cash before he could make his dream a reality. Instead, he bought a steamship and used this to connect his railroad with the city of San Francisco. And while the businessman made a number of attempts to realize his vision, he eventually had to admit defeat.
As a result, the Oregon Pacific Railroad petered out at Idanha – some 15 miles away from the Cascades. This meant the nearby turntable at Old Detroit became one of the last stops on the line. Yet despite the remoteness of the station, it was often busy with loggers transporting timber eastwards by rail.
At one point, Old Detroit was a thriving community that played host to a number of cafes along with a cinema, a church, a hardware store and a school. However, for farmers living further down the valley, life was often a struggle. The North Santiam River passed through the nearby Cascade Mountains, swelling with rainfall and snowmelt as it went. Eventually, it would come crashing through the nearby towns, wreaking havoc along the way.
“For farmers and boosters in the Willamette Valley, the North Santiam made life hell,” Oregon historian Bob Reinhardt told the Statesman Journal in 2015. “Gathering snowmelt and rainfall in the Cascades, the river contributed to floods that washed through Salem and other valley towns, sometimes causing millions of dollars in damage.”
However, in 1938 Congress passed the Flood Control Act, which permitted the use of civil engineering programs to help combat damaging deluges in the United States. And in the Willamette Valley itself, developers came up with a plan. By constructing two dams, they realized, they could solve the area’s flooding problem and produce electricity at the same time.
Like Hogg before them, the masterminds behind the Detroit Dam thought big. Upon its completion, the dam would stretch 1,580 feet from end to end and tower 360 feet tall. It was also envisioned that the great structure would be able to contain 455,000 acre-feet of water from the North Santiam River when it finally went into operation.
Unfortunately, there was one small problem with these grand plans for a new dam. Apparently, the barrier would require 3,580 acres of space – including the use of the land where Old Detroit stood. And so in the name of progress, the railroad town’s residents prepared to leave their homes behind for good.
According to records, the soon-to-be displaced locals asked the government for land on which to build a new town. But while authorities denied the request, fortunately all was not lost. At that point, a local timber merchant stepped in, offering the use of an old logging site instead. And by the summer of 1952, many members of the Old Detroit community had purchased plots at this new location.
There, on a hill above the old town, residents re-established the community of Detroit – even keeping the same name. Some families went so far as to dismantle their dwellings piece by piece, dragging them by sled to the new site. And even today, the streets contain some buildings that were relocated in this strange manner. These structures almost certainly wouldn’t have survived if they’d stayed in place.
You see, in 1953 the dam – the fifth largest of its kind in the country – went into operation. As a result, the river became a lake that would quickly swallow the rooftops of Old Detroit. And yet on days when the waters are at their lowest, the curious can still sometimes see the ruins that remain.
In fact, in October 2015 the few people lucky enough to catch a glimpse of Old Detroit were in for a particularly spectacular sight. And the remnants of the former town definitely weren’t the only relics to be exposed as the water waned. There was also a 19th-century wagon that, thanks to the low oxygen levels in the lake, was incredibly well-preserved.
“I went on a treasure hunt down along the river, figuring I’d find foundations or something like that,” Dave Zahn, a Marion County sheriff’s deputy, told the Statesman Journal in 2015. “Then I saw a piece of old history right there.” The wagon, which dates back over 140 years, was most likely used to carry goods, and it had emerged from the lakebed lying on its side.
Furthermore, a plaque on the vehicle declares that it was produced by the Milburn Wagon Company in 1875. Based in Toledo, Ohio, the company was the biggest manufacturer of wagons on the planet at the time. And according to Cara Kelly, an archeologist with the U.S. Forest Service, this particular example may have played a part in the construction of the local railroad – at least, before it was left to its watery fate.
Over the years, however, the usefulness of wagons such as this one waned. And by the time residents abandoned Old Detroit, automobiles had essentially replaced these old-fashioned carts. No longer needed, they simply sat empty and forgotten, eventually succumbing to the same fate as the rest of the town.
And the wagons were apparently constructed to last – explaining just how the Old Detroit example remained intact for so many years. Speaking to the Statesman Journal in February 2020, David Sneed from the vehicle archive Wheels that Won the West explained, “That wagon was built for the country that you’re in. With those extra spokes, the metal-encased hubs and the ‘Oregon brake,’ it’s built to engage rough terrain.”
Interestingly, though, the cart wasn’t all that eagle-eyed observers managed to spot in Detroit Lake, as the low waters also revealed a type of octagonal-shaped pit coated with cement. But even though the mysterious hole stood out sharply against the cracked, dry reservoir bed, experts were unable to determine what its original purpose might have been.
And while Zahn was delighted to be among the lucky few to glimpse the wagon, he also had concerns that vandals might destroy the historical find. Kelly seemingly concurred, as he asked residents to keep the discovery’s exact location to themselves. “I don’t think people realize they aren’t supposed to collect items off public land,” she told the Statesman Journal in 2015. “But once someone removes something, nobody else will get to see that piece of history.”
Then, in late 2015, the wagon went viral. And as its story spread across the country, a group of local business people asked themselves questions. Could they somehow excavate the relic and display it in Detroit as a permanent attraction? Unfortunately for the budding entrepreneurs, Kelly was quick to shoot down this proposal.
“The issue is that in trying to remove [the cart], it would just fall apart,” Kelly told the Statesman Journal in February 2020. “It would just crumble. It’s also half-buried in the mud.” So, even if experts could somehow excavate the wagon, it would need storing in a specialist facility – and nothing suitable to the task currently exists in Detroit.
Amazingly, too, Kelly believes that the 2015 appearance could have been the wagon’s first since having been swallowed up by the lake over 60 years ago – although she does also think that it may have traveled from elsewhere. “This might not have been [the wagon’s] original resting place,” the U.S. Forest Service employee claimed. “It could’ve come from anywhere in the town of Detroit. The flood of 1964 moved a lot of things; it even brought houses down.”
Kelly also thinks the wagon’s time above water may have caused more deterioration than its six decades spent submerged. Perhaps luckily for the vehicle, then, its wheels were destined to disappear beneath the surface once more. But that wasn’t quite the end of the story.
In 2019 concerns were raised about the future of the lake as well as any relics submerged beneath its waters. Since the dams’ construction, the wild fish population of the Willamette River has reportedly seen a drastic decline. In particular, it’s thought that the structures both damaged the marine dwellers’ natural ecosystem and closed off their spawning grounds from the rest of the river.
So, in response to a 2008 legal agreement designed to protect species such as steelhead trout and wild salmon, the U.S. Army Corps of Engineers put forward a solution. By constructing a 300-foot tower at Detroit Dam, the engineers claimed, they could reverse the negative effects on the fish’s habitat. The team also submitted a design that would help round up migrating fish and relocate them safely downstream.
However, these developments came with one small catch. In order to construct these solutions, engineers explained, they need to drain the reservoir to as low as 1,310 feet – below even the drought levels of 2015. What’s more, these measures could remain in place for an entire summer, and this is likely to deliver a hard blow to tourism in Detroit.
In fact, the project – which is yet to begin – has apparently drawn criticism from locals whose livelihoods depend on the reservoir. And the custodians of the relics of Old Detroit may also have cause for concern. After all, prolonged exposure to the elements caused damage to the wagon in the past, and so a whole summer above water could prove disastrous.
Four years after the wagon made its star appearance, however, repairs to the dam caused the amount of water in the reservoir to decrease once more. This meant the historic relic was again visible. And in December 2019 photographer Jeff Green managed to locate the fascinating site after three days of searching.
Seeing the wagon in person was a memorable moment for Green, too. Speaking to the Statesman Journal in February 2020, he explained, “Oregon has few such relics. To see this history appearing in the mud was surreal. It was a moment that doesn’t happen very often – like the solar eclipse.” The photographer pointed out, though, that the area around the wagon contained a treacherous quicksand-like mud, making it challenging to reach.
And with the wagon’s reappearance, concerns grew once more that looters might damage the historic artifact. Yet Zahn told the Statesman Journal that he was not overly anxious about the situation. “[The wagon’s] very difficult to reach and almost always underwater,” he explained. “I’m happy that it happened and glad whenever someone talks about it or says they’ve seen it.”
Then, in January 2020, the water in the reservoir reached more normal levels, and the wagon vanished again. Still, it wasn’t long before yet another threat emerged – this time in the form of a drought. In March that year, experts grew concerned that a lack of precipitation could cause Detroit Lake to dry out. And if this were to come to pass, the relic would once more be at risk from both looters and the elements.
For now, however, the wagon remains beneath the water, where it continues to be a source of inspiration. Speaking to the Statesman Journal, photographer Brent McGregor explained the cart’s appeal. “The real beauty with this one is that it’s still out there, sticking out of the mud and well-preserved,” he said. “You can use your imagination and think about the old town. It’s great to have it there.”