Somewhere in a laboratory in Germany, a researcher gets surprised by what she had discovered. She had to do a double-take and re-examined her notes to make sure that no mistakes were made in coming up with the conclusion. But based on the evidence, the findings were legit.
Source: Atlantic Mirror
The ancient remains that she was studying show that this girl was born from two different species. The significance of this unexpected finding would mean that what history and science have known about human evolution is about to change from this point on.
Taking a chance
This all started when a research team found a tiny bone fragment in a cave in Siberia. At that time, they did not even realize that it was hominin. Hominin is a term used for all species that were regarded as human.
Source: Atlantic Mirror
That particular bone was not given much thought and was set aside for years. Then, researcher Viviane Slon had her hands on the said bone and tried to see if she could extract DNA from it. What she found later on in the German laboratory may change everything we know about ancient humans.
History in the making
As mentioned earlier, the bone showed that the owner was a hybrid – an offspring born from two different species. This discovery marks the first time that a direct ancient human hybrid had been found. This was history in the making!
Source: Atlantic Mirror
As we all know, modern humans have emerged from the same species, Homo sapiens. This specie walked the earth about 300,000 years ago. But, if you put into consideration prehistoric times, you will find that there are a couple of human-like species that walked the earth.
The earliest humans
The earliest human ancestors ever known were called the Australopithecines, who first emerged in Africa about 4 million years ago. These species were capable of walking and climbing using their two legs, but back then they looked different from Homo sapiens.
Source: Atlantic Mirror
It was after the emergence of the Australopithecines that the different species of Homo started to emerge. These new specie variations had long legs that were more suitable for a movement like running and walking. They also had bigger brains. These species were now able to hunt and feed on meat.
The Homo heidelbergensis
The variation of Homo species that started to closely resemble modern people in looks was the Homo heidelbergensis. They emerged in Eurasia and Africa about 700,000 years ago. And these hominids behaved very differently from the species that came before them.
Source: Atlantic Mirror
The Homo heidelbergensis were more intelligent. They were able to create tools for hunting. They were also able to come up with different hunting techniques that made them team up to bring down larger animals.
The unsettling discovery
Despite their improved intelligence, the species eventually died out as well. But before the last of the species was over, several different species had already split off from it about 390,000 years ago. It is from these branches that modern humans would emerge.
Source: Atlantic Mirror
Over the millennia, it was acknowledged that some hominin species existed at the same time. Although it was often suggested that some may have even practiced interbreeding with a hominin of another species, there was really no proof of it. That is, until Viviane Slon’s discovery in the Max Planck Institute for Evolutionary Anthropology.
The likelihood of interspecies breeding
It has often been said that members of different species will not be able to interbreed successfully. But this is hardly a fact. For instance, we now have the mule, which is bred from a horse and a donkey. But there is also the fact that as a result of the interspecies breeding, most mules are infertile.
Source: Atlantic Mirror
Sexual reproduction needs the sperm and egg to have 50% of each of the chromosomes. The horse has 64 chromosomes and a donkey has 62 chromosomes. Because of this, the mule ends up with 63 chromosomes. This odd number means that the genetic code will not work for reproduction.
Successful interspecies pairing
But as science would point out, the outcome of inter-species breeding varies according to the DNA of the animal. For one, some primate species have the same numbers of chromosomes. If they breed, they can produce healthy offspring that can reproduce. Chimpanzees and bonobos are known to interbreed.
Source: Atlantic Mirror
Some big cats also have the same number of chromosomes. One example is the liger, which is an offspring of a tiger and a lion. Ligers are also known to be able to reproduce healthy offspring.
Interspecies breeding in hominins
In the case of early humans, it was assumed that they also have the same amount of chromosomes. This means that if they did interbreed, it would be a successful pairing and their offspring will be able to reproduce.
Source: Atlantic Mirror
In fact, some experts believe that the Homo sapiens had mated with Homo neanderthals when they migrated from Africa and started to explore the world. This is assumed to be the reason why most Europeans and Asians have 2% Neanderthal DNA.
The Denisovans
As it turns out, the Homo sapiens did not just mate with Homo neanderthals. Some Homo sapiens have found their way to another branch of the human ancestry – the Denisovans. Some of you may never have heard of them before because the Denisovans were just discovered in 2010.
Source: Atlantic Mirror
A team of experts from the Max Planck Institute of Germany studied a finger bone and tooth that was found in a cave in the Altai Mountains, Siberia. What they discovered is evidence of a new hominin species. The new early human species was named Denisova after the Denisova cave, in which the ancient fragments were found.
A bone is rediscovered
The discovery of the Denisovans was a monumental breakthrough in history. But aside from what could be analyzed through DNA, nothing much is known about them. So, in 2012, another research was conducted in the Denisova cave where they found the small bone fragment.
Source: Pixabay
The small bone fragment was actually mixed in together with the hundreds of animal fossils unearthed from the cave. It took a few years for the bone fragment to be identified as human. This only happened when Samantha Brown from the University of Oxford, got tasked to catalog the artifacts.
The bone is human
Samantha Brown took a closer look at the bone fragment when she analyzed the protein content of the bone. It was then that she realized the bone was human – possibly an early human, like the Denisovans.
Source: Atlantic Mirror
With this discovery, the bone was sent to Viviane Slon, who was a paleogeneticist. Slon immediately busied herself with the mystery hominin by investigating the DNA within the bone fragment. This was when the startling discovery was made.
Maternal ties
At first, the bone did not seem to hold anything remarkable. It was just a small fragment – an inch long. It was found later on that the bone fragment belonged to a 13-year-old girl who died about 90,000 years ago. This was about the time when the Denisovans had occupied the Altai Mountains.
Source: Atlantic Mirror
Viviane Slon analyzed the DNA in the mitochondria of the bone. As it is known, this structure only contains DNA from the mother. And what Slon saw was a surprise. The DNA suggested that the teenage girl’s mother is a Neanderthal.
Paternal ties
Viviane Slon got excited with her discovery as this meant that she may be looking at proof of inter-species breeding. To prove this, she had to start looking for the nuclear DNA, which is passed from both the mother and the father.
Source: Atlantic Mirror
In the search for the nuclear DNA, Slon confirmed that the father of the teenage girl was a Denisovan. But that was not enough proof for Slon. A discovery this big should be covered at all bases. Slon then discovered something odd in the girl’s genetic makeup.
Heterozygosity
It all boils down to heterozygosity. This means the inheritance of different forms of a particular gene from each parent. Offspring who are the result of inter-species breeding would have sky-high levels of heterozygosity.
Source: Atlantic Mirror
The bone had very high levels of heterozygosity, which confirmed that this teenage girl, was a result of interbreeding. Slon had been able to make a significant contribution to her field by discovering the first-generation offspring of interbreeding between two different hominin species.
The holy grail of evolution
Viviane Slon’s lucky break and discovery had shocked experts in the field of evolution. What were once assumptions of interbreeding was finally confirmed. There now was actual proof of a first-generation hybrid and she was given the name Denny.
Source: Atlantic Mirror
The discovery was an unexpected surprise that it had raised questions about how common interbreeding really was for the early humans. If interbreeding were done regularly, this would mean that all understanding of human evolution would be put into question.
Genetic research on interbreeding
The discovery of Denny had encouraged experts to do a thorough genetic research on a small number of ancient humans artifacts. The question of how often interbreeding took place had to be answered as this could disprove everything about evolution.
Source: Atlantic Mirror
Twenty-three ancient human remains had been studied up to 2018 and it has been found that at least two specimens were a result of interbreeding. And this is just a tiny sample. It makes one wonder how much more interbreeding evidence could be found in a large sample of ancient human remains.
The case of Oase 1
One ancient human case stood out. The individual was dubbed as Oase 1. Oase 1 was thought to emerge about 37,0000 years ago. But then, a closer look at the remains determined that Oase 1 had been carrying Neanderthal genes. If interbreeding was not a common thing, there would have been fewer discoveries like that of Denny and Oase 1.
Source: Atlantic Mirror
In fact, Max Planck Institute also did more research on Denny. It turned out that Denny’s father had both Denisovan and Neanderthal DNA. He was a result of interspecies breeding too! The discovery about Denny, her father, and Oase 1 was revealing. This suggests that inter-specie breeding had been going on in hominins frequently and probably occurred earlier than what they have realized.
Changing history
Before Denny, researchers assumed that interactions between the different hominin species rarely happened. The world was so wide and the possibility of these different groups meeting and interacting was not really considered.
Source: Atlantic Mirror
But because evidence of interspecies breeding is now turning up, this means that different species had been interacting frequently. This changes everything we know about ancient humans and how our society had evolved.
The Denisova cave
Questioning the possibility of a first-generation hybrid appearing in a limited sample size brings us back to the Denisova cave. It had been suggested that a cave in the mountains such as the Denisova cave is a good and popular choice of shelter for ancient humans.
Source: Atlantic Mirror
If two groups had been living in proximity to that cave, it would be no surprise that they would eventually end up meeting each other there. But did interbreeding really just happen because of location and proximity?
A means of survival
According to Katerina Harvati-Papatheodorou from the University of Tübingen, other factors may be at play when it comes to interspecies breeding among the hominins. According to her theory, it could be a means of making the species survive.
Source: Atlantic Mirror
Most ancient human groups were small in size and the mortality rate was drastically short. They may be aware of other groups dying out at some point. Breeding with another group may be seen as a means to reproduce and grow in numbers.
Finding answers
So what happened to the Denisovans and Neanderthals that interacted in the Denisova cave? Did they die out as the other hominin species did? Or did the crossbreeding mean that the new generation was considered as a newer and more dominant species?
Source: Atlantic Mirror
As more information is being unearthed regarding this matter, experts are excited that there will be more revelations and hopeful that some mysteries will be solved. The scientific community is very hopeful that the discovery of Denny could lead them to the missing piece of the evolution puzzle.