- As anthropologists have discovered new species of human ancestors, our understanding of human history has changed.
- By sequencing the genomes from our Neanderthal and Denisovan cousins, scientists have also gained new insight into the genetic origins of our species.
- As researchers make more of these breakthroughs, the puzzle of who we are and where we came from gets more complicated.
- The earliest humans may have emerged much earlier, and in a different place in the world, than scientists previously thought.
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In recent years, anthropologists around the world have discovered new human ancestors, figured out what happened to the Neanderthals, and pushed back the age of the earliest member of our species.
Taken together, these breakthroughs suggest that many of our previous ideas about the human origin story – who we are and where we came from – were wrong.
Until the past few years, most scientists thought the first members of our species, Homo sapiens, evolved in East Africa approximately 200,000 years ago. Then humanity remained in Africa for the next 140,000 years, according to this line of thought, before venturing into Europe and Asia in what’s known as the “Out of Africa” migration about 60,000 years ago. Those early humans proceeded to take over territories once occupied by other human ancestor species like Neanderthals.
But this understanding of history has been upended as new discoveries revealed that the first humans emerged much earlier than we thought and in a different part of Africa. Rather than simply replacing other competitor species, Homo sapiens seem to have interbred with them.
As researchers make more of these breakthroughs, the human evolutionary puzzle gets more complicated.
A 2017 finding in Morocco threw into question the idea that modern humans originated in East Africa. Those bones were significantly older than any others ever found.
Researchers determined that the bones unearthed in Morocco's Jebel Irhoud region were 315,000 years old - roughly 100,000 years older than the bones previously considered oldest modern human fossils. (Those fossils, found in Ethiopia, were roughly 196,000 years old.)
The remains were also found in a different area of Africa than most other ancient human bones: North Africa instead of East Africa. That suggests our earliest ancestors may not have lived in just one part of the continent.
"There is no Garden of Eden in Africa, or if there is, it is all of Africa," the anthropologist Jean-Jacques Hublin, who led the Morocco expedition, said at the time.
This discovery supported a new idea about human evolution: Perhaps Homo sapiens evolved all over Africa in interlinked groups that became more similar over time.
A team of researchers suggested in 2018 that groups of Homo sapiens might have evolved simultaneously all over Africa instead of in one primary location.
Not all of these groups would have looked identical at the start, the scientists said, but they may have been genetically close enough to all be considered Homo sapiens.
According to this line of thinking, distantly related groups of humans across the continent could have become more similar over time instead of first emerging in one area of East Africa then spreading from there.
Still, based on recent genetic analyses, researchers think anatomically modern humans may have all originated in modern-day Botswana.
A study published in October suggested that every person alive today may have descended from a woman who lived about 200,000 years ago in what is today part of Botswana. Researchers narrowed in on that location using genetic analysis of DNA that gets passed down the female line.
The finding supports the theory that modern human ancestors migrated out of Africa then populated the world, rather than evolving in different pockets around the globe simultaneously.
The ability to sequence ancient genomes is helping scientists learn about what our ancestors ate, how they looked, and where they came from.
Typically, ancient DNA is extracted from bones. But in December, anthropologists sequenced an entire genome from a piece of 5,700-year-old chewing gum.
The analysis revealed that the person who chewed the 2-centimeter piece of birch pitch was a woman with dark skin, dark hair, and blue eyes. Nicknamed Lola by anthropologists, this human ancestor had dined on duck and hazelnuts before chewing the gum.
DNA analysis has also revealed that, rather than outcompeting and eliminating our ancient Neanderthal cousins, modern humans interbred with them extensively.
Geneticists finished sequencing the entire Neanderthal genome in 2010. That led them to realize that Neanderthals interbred with modern humans quite a bit. The idea that Homo sapiens killed off and replaced the Neanderthals was eschewed in favor of the hypothesis that the two species became one.
It turns out that Homo sapiens interbred with another human ancestor species, Denisovans, as well.
Denisovans disappeared about 50,000 years ago, but not before passing on some of their genes to Homo sapiens, according to a 2018 study. Denisovan DNA can be found in the genes of modern humans across Asia and some Pacific islands. Up to 5% of modern Papua New Guinea residents' DNA shows remnants of interbreeding with Denisovans.
People in Tibet today also possess some Denisovan traits; that could even explain how Sherpas are able to weather high altitudes.
Scientists discovered Denisovans after finding a tiny, lone finger bone in a Siberian cave.
Anthropologists found the bone in March 2010. A genetic analysis revealed that Denisovans were an enigmatic offshoot of Neanderthals.
Thus far, fossilized Denisovan remains have been found only in the Denisova cave in Russia and in Tibet.
Since the discovery of the Denisovans, anthropologists have also found several other species of human ancestors in Africa and Asia. Our own ancestors may have lived alongside or even mated with them.
In April 2010, the anthropologist Lee Berger announced that he and his son had found a new species, called Australopithecus sediba, in Malapa, South Africa.
Australopithecus sediba had teeth and lower limbs that resembled those of our own Homo genus. The ancestors' legs and feet were adapted to walking upright on two legs.
Berger's team announced the discovery of another new human ancestor species in South Africa five years later. It's called Homo naledi.
Two spelunkers accidentally stumbled across the Homo naledi fossils in a hidden cave.
All told, the chamber contained 1,550 bones belonging to at least 15 individuals who lived between 330,000 and 250,000 years ago. The timeline suggests this human ancestor might have lived alongside early Homo sapiens in Africa.
Anthropologists found teeth and a finger bone from yet another human ancestor in the Philippines in April 2019. The species was a precursor to Homo sapiens.
The newly discovered species, named Homo luzonensis after the island where it was found, lived between 50,000 and 67,000 years ago.
The ancestor shared traits with older human ancestors like Australopithecus and Homo erectus, as well as with modern-day humans.
Before these recent findings, anthropologists thought our ancestors left the African continent in one mass exodus about 60,000 years ago.
But according to a study from 2017, the first Homo sapiens may have left Africa and started migrating into Asia more than 120,000 years ago - far earlier than scientists had thought.
"The initial dispersals out of Africa prior to 60,000 years ago were likely by small groups of foragers, and at least some of these early dispersals left low-level genetic traces in modern human populations," Michael Petraglia, an author of that study, said in a press release. "A later, major 'Out of Africa' event most likely occurred around 60,000 years ago or thereafter."
The Homo sapiens involved in that "Out of Africa" wave gradually spread into Europe, Asia, and the Pacific.
A 210,000-year-old skull found in Greece may push that migration timeline even further back.
The skull belongs to the oldest modern human discovered outside Africa. It predates what researchers previously considered to be the earliest evidence of Homo sapiens in Europe by more than 160,000 years. (Anthropologists had previously discovered modern human remains between 42,000 and 45,000 years old in Italy and the UK.)
Another modern human jawbone found in Israel was determined to be 177,000 years old, adding further credence to the idea that Homo sapiens left Africa far earlier than 60,000 years ago.
Kevin Loria contributed to a previous version of this story.