What they were aware of, though, were two other concepts that describe evolution.

These are:

1. Descent with modification
2. Common descent.

The first is an observable fact. Children look different from their parents and siblings. Despite being descendants of their parents, children are modified versions of them.

The common descent theory suggests that living beings on Earth all share a common ancestor. Descent with modification over numerous years has resulted in all the species variety we see. But, it’s also a theory we can’t observe. Over the years, scientists have described a model common descent. However, at the time, researchers could not fathom how random genetic changes could guide descent with modification to create species variety from a single ancestor.

Charles Darwin’s theory of natural selection changed all of that. He suggested that while random variations may have been wrought by nature, nature had also helped select organisms that were most likely to survive. Over time, organisms that do well, flourish, as do their offspring. Eventually, enough of the offspring with useful characteristics survive and alter the species as a whole.

Darwin’s belief in natural selection being an essential step for evolution has been proven, to some degree. Researchers have observed it in the lab and outside, making natural selection an observable fact. Common descent is a bit harder to prove.

How was Natural Selection Discovered? 

In 1859, Darwin laid the foundation for the field of evolution when he put forward his theory of natural selection. His travels to South America and Europe aboard the H.M.S. Beagle had brought the variety of the natural world into his line of vision.  

He theorized that differences in needs and responses to one’s environment led to certain traits being favored over others. This ability to adapt to one’s surroundings made one more or less likely to survive. Naturally, during reproduction, organisms with those traits outperformed those without. Gradually, such organisms flourished and evolved.  

How Does Natural Selection Work?  

According to Darwin, the adaptation of organisms to their environs happened through natural selection. This process arises from a random accumulation of favorable genes. The fittest individuals were those who possessed the genes needed to survive their environment.  

The theory of natural selection was the crux of Darwin’s proclamations during the 19th century. Simply put, genes that increase an organism’s chances of survival are more likely to appear in a population. Eventually, genes that reduce fitness are ruled out.  

A well-known example is that of the evolution of dark moths in England. Prior to the industrial revolution, a light grey moth, which was easily camouflaged between the lichen growing on trees was the most common variety in the country. But after the industrialization of the nation, pollution turned the barks of trees black, making darker moths more likely to survive scavenging birds. 

Over time, natural selection made black moths a more common feature in cities as opposed to the rural areas that still bear witness to the lighter variants. Thus, environmental constraints had weeded out the “weaker” moths. “Fitter” moths that could withstand predation eventually overtook the natural population. 

Natural selection vs artificial selection 

While natural selection occurs well, naturally, artificial selection requires a helping hand—most often from man. The domestication of the dogs we have as pets and the crops we like to eat are a direct result of man’s interference in evolution. Humans have selectively bred many species useful to them by choosing to breed only those with traits we valued.  

 Horses have been bred for speed, cows for milk production, and dogs for size, cuteness or ferocity. Artificial selection has not interfered with nature in multiple ways. For example, the wild mustard of yore is the ancestor of not only the cabbage of today but also that of brussel sprouts, kale, cauliflower, and kohlrabi.  

3 Requirements for Natural Selection 

For natural selection to occur, certain requirements need to be met: 

1. Organisms within a species can differ from one to the other. These variations can include color, size, markings, etc. But other traits, say the number of chambers in a human’s heart, will remain constant within the species.  
2. Certain traits are heritable and passed from parent to offspring.  
3. Populations tend to overproduce but are kept in check by disease, famine, or other limitations. Individuals within a species must compete for resources.  

Variations that help organisms adapt to their environs are retained and herited. Thus, over time, populations evolve through natural selection. Only those individuals who can adapt to their environment pass on suitable traits to their progeny and survive.  

Natural selection in humans 

The mechanisms of natural selection are well observed, however explaining human origins gets more complex. Historically, it was thought modern humans evolved to beat out other species. Researchers long suspected that one reason humans may have vanquished Neanderthals is because we were more adaptable. However Neanderthal DNA in modern human genes show that’s not exactly the case.  

Humans have colonized the far corners of the world. These varying environments have left their mark on the human genome in the form of adaptations. Till date, close to 3000 regions associated with natural selection being identified in the human genome. These include changes in the genes that help people digest milk or acclimate to high altitudes. 

One example of natural selection in humans is the skin tone gradient seen across the world. To begin with, humans were likely pale under thick fur. As we lost most of our body hair—likely to keep us cool in hot Africa—we grew darker-skinned.  

 Today we can explain these changes via epigenetics. A genes ability to shift its expression with environmental changes. It adds a level of complexity to ‘random’ mutations.  

Melanin, the pigment in our skin kept us protected from the sun’s UV rays. Dark skin in the tropics help prevent the breakdown of folate, an important vitamin. As humans spread out of Africa, lighter skin evolved in regions of the world where sunlight is not as harsh. Light skin in the temperate zone helps in vitamin D storage.  

 Another example is human tolerance of lactose, the sugar in milk. When domestication had not made milk easily accessible to humans, lactose intolerance was widespread. Now, large scale dairy farming has almost led to the disappearance of this trait. 

Conclusion  

Natural selection in evolution is an observed phenomena. However, new advances in biological diversity and genetics, show there are still many things to learn to explain the evolution of a complex species like the human race.   

Today you can still detect the vestige of these legacies in our genome.  

When we consider evolution an explanation for all life on earth, it must be acknowleged that part of the theory is still being uncovered by scientists.  

Further reading:  

https://plato.stanford.edu/entries/natural-selection/ 

https://www.amazon.com/Life-Science-William-K-Purves/dp/0716798565  

https://www.amazon.com/iGenetics-Molecular-Approach-Peter-Russell/dp/0321569768  

https://www.amazon.com/Biology-8th-Neil-Campbell/dp/0805368442  

https://academic.oup.com/nar/article/47/D1/D1080/5134333  

http://blogs.discovermagazine.com/crux/2019/01/28/human-skin-color-explained-vitamind-folate/#.XGLipTMza00 

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Most people today have heard of the Out of Africa theory for human evolution. It was back in the 19th century, when Charles Darwin suggested that our human ancestors may have evolved in Africa. It was based on the fossil records uncovered at the time. In the next century, two theories were floated to explain paleo-anthropological records.   

The other, is called the multi-regional hypothesis. It proposes that long ago, after exiting Africa, multiple homo species settled throughout the world. Modern humans then evolved from these ancestors across different locations worldwide.  

According to the multi-regional hypothesis, the ancestor, Homo erectus, seeded Homo sapiens populations all over the world. Proponents explain the rise of modern human DNA from a continuous exchange of genetic material occurred over a span of hundreds of thousands of years.   

The Out of Africa theory describes a much simpler and recent evolution of modern humans, moving from Africa to Eurasia and then globally.  

To this day Out of Africa, is widely accepted theory among scientists.  

However the alternate has a growing body of evidence to show that modern humans could have been outside Africa at an earlier than established date. 

How was the Out of Africa Theory Established? 

Out of Africa was only established in the 90’s during a debate as to the age of modern humans.  

The development of genetic analysis tools in the 1980s helped scientists grow attracted to the out of Africa hypothesis. Matches between the DNA of living modern humans and fossil remains verified that H. sapiens evolved several hundred thousand years ago on African soil. 

The theory explains that while numerous human-like species walked the planet, only one arose into modern man. 

New evidence continues to swing the pendulum of knowledge about human origin between these two theories.

When did Humans Leave Africa? 

Image: An overview of the Out of Africa Theory Map Source

Today it’s still far more accepted that humans are a relatively young species.  

Out of Africa theory says the first modern man first evolved in Africa about 200,000 years ago. Further, the single and original H. sapiens was believed to have travelled out of Africa around 70 000 years ago. 

It’s believed that several branches of modern humans, beginning around 270 000 years ago, and certainly 130 000 years ago came out of Northern Africa. These waves were either died out or retreated, before the last and final wave travelled across the globe.  

Successful modern humans were said to have replaced ancient humans (like the Neanderthals) without mating with them. In recent years, new discoveries have challenged multiple aspects of this theory.  

Recently, researchers presented their discovery of H. sapiens fossils from Morocco. Called Jebel Irhoud, the bones were dated back to around 315,000 years ago.  

The finding of the bones of a modern humans in Africa at such an early date pushes our origin story back by more than 100,000 years.  

Other studies have also suggested that an early migration out of Africa may have occurred around 120,000 years ago.  

To make things even more interesting, in recent years, Neanderthal DNA evidence suggests modern and archaic humans may have interbred.

How and when did humans migrate out of Africa? 

A problem confounding scientists is when and how many types of humans resulted in our modern form.   

Scientists are of the opinion that humans may have taken a few different routes on their move out of Africa. Recent evidence also suggests that there may have been more than one exodus. These waves of migration out of the continent likely happened at different time points. 

One route taken by the early humans was likely across the Bab-al-Mandab Strait that runs between Yemen from Djibouti. From there, they quickly moved along coastal India, reaching Southeast Asia and Australia around 50,000 years ago.  

Another group moved into the Middle East and southern Central Asia a little after 50,000 years ago. Then, the modern humans moved across Europe and the northern reaches of Asia.  

Who were the First Humans in Africa? 

Previously, the oldest H. sapiens fossils were thought to be from the Omo Kibish and Herto sites in  Ethiopia that are dated to around 195,000 and 160,000 years ago, respectively.  

The recently discovered specimens, Jebel Irhoud (Morocco) and Florisbad (South Africa), were dated to about 315,000 and 259,000 years ago, respectively. These “new” remains imply modern man evolved much earlier than anticipated. 

Outside Africa, the oldest known H. sapiens fossils were at two sites in Israel, Skhul and Qafzeh, and had been dated to only between 90,000 and 120,000 years old. But a recent finding of a jaw bone in Misliya cave, Israel, has pushed the date of modern man’s first migration back much further.  

According to the researchers, early humans may have wandered out of Africa more than 50,000 years ago than previously thought. The fossil, which includes a part of the upper jaw and teeth, was dated to between 177,000 and 194,000 years ago.  

The scientists made an anatomical comparison between the fossilized jawbone and those of other human species. It was found to most similar to that of H. sapiens. There are some scientists that say more evidence may be needed. All in all, these results suggest modern man may have been present outside of Africa more than 50,000 years earlier than previously believed.  

These and other fossils  suggest that H. sapiens may have evolved at multiple places in Africa. This development goes against the previously-held theory that humans arose at a particular place in Africa.  

Indeed, modern humans may have arisen at multiple spots. 

Why did early humans migrate Out of Africa? 

While researchers aren’t quite clear on why humans may have been driven to move, they suspect climatic changes. The dramatic cold possibly made life quite uncomfortable for early humans.  

Changes in the African continent’s climate may have forced modern humans to seek greener grass elsewhere. 

Out of Africa Theory vs Multi-Regional Theory  

In 1927, near Beijing Davidson Black uncovered the remains of a human-like ancestor that would rock the world of anthropologists. Originally a single tooth, excavations would reveal several skullcaps and mandibles, facial and limb bones of 40 skeletons. The dating of the fossils revealed a time span of between 7700 to 230 000 years ago.  

Franz Weidenreich, a German anthropologist used the findings to help develop the multi-regional approach to understanding human evolution. His study of Peking Man—a H. erectus fossil found in China—led him to conclude that similarities between past and present human species in the region must have arisen from evolutionary continuity.  

The Java Man—a H. erectus fossil from Indonesia—left Milford Wolpoff, an American palaeoanthropologist, similarly convinced. He went on to coin the term “multi-regional hypothesis” in the 1980s.  However, recent dating of later H. erectus in Indonesia imply they only lived until about 50,000 years ago when modern humans from Africa may have come.  

On the other hand, China showcases examples of skulls from 100,000 years ago that seem to fall halfway between H. erectus and H. sapiens. 

Conclusion 

New fossils and discoveries are constantly rewriting the history of modern humans’ movements outside of Africa. Only recently scientists have found evidence that modern humans may have evolved more than 300,000 years ago.  

This pushes back old estimates by over a hundred thousand years. Newly found remains also suggest that the first wave of migration may have occurred earlier than 50,000 years than we initially believed.  

Multi-regional evolution could see a renewal in popularity as new pieces of the puzzle are added in. At the very least, changes to the Out of Africa theory is now occuring.  

Our understanding of the reasons behind the move out of the continent will only deepen as our clarity on the timelines grows. This will only happen as more and more fossils are dug up around the world. 

Human evolution, is evolving.  

Further reading:  

http://www.bbc.co.uk/worldservice/africa/features/storyofafrica/2chapter2.shtml 
https://www.scientificamerican.com/article/controversial-fossil-hints-homo-sapiens-blazed-a-trail-out-of-africa-earlier-than-thought/ 
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4844272/ 
http://science.sciencemag.org/content/359/6374/389 
https://www.sciencemag.org/news/2018/04/human-finger-bone-points-early-exodus-out-africa?r3f_986=https://www.google.com/ 
https://genographic.nationalgeographic.com/human-journey/ 
https://psmag.com/news/why-and-when-did-early-humans-leave-africa 
 

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Charles Darwin’s theory of evolution is widely regarded as the best explanation for life on earth. Most people today believe that all species on Earth evolved from a common ancestor. In response to varying environmental conditions, members of a species acquire mutations that made them more likely to survive compared to other members of their species. Over time, useful—but spontaneous —mutations prevail and species evolved. 

Today scientists are building new ways to understand the evidence for evolution.  

Darwin’s work laid the foundation for the field of biology to research the evolution of species. It led the study of the reasons underlying species variation. It also provided an explanation for the differences between individuals in a species and why these differences matter for populations to evolve.  

There are also things about life on earth, that to this day we don’t understand.  

Let’s explore the evidence of evolution, from its history and scientific analysis, since Darwin published the Origin of Species.  

The History of Evolution

In 1859 Darwin presented his paradigm-changing evolutionary theory of natural selection. It was not well accepted and received broad criticism. Today many people still disagree with the theory of evolution. However, that is the nature of scientific progress.  

Darwin wasn’t the only advancement in building the evidence for evolution.   

Over the course of the past century or more, the discoveries of Gregor Mendel, James Watson, Francis Crick, and several other biologists have added to our understanding of genes, natural selection, and evolution.  

Before Darwin, philosophers and scientists had put forth theories that laid the foundation for evolution. Going back thousands of years, various entities had speculated about the origin of species.  

Creation vs. Evolution 

The theory of evolution began with ideas founded in creation or creationism. 

Let’s look at the timeline of how creation, became a theory of evolution. Several theories put forward before Darwin’s time had had some level of Creationism. 

• In the 1700s, Carolus Linnaeus—famous for his system of nomenclature and classification—suggested that many species were hybrids that had evolved from others placed on Earth by God.  

• In 1794, James Hutton, a leading geologist, was the first to theorize natural selection, without terming it as such. Hutton used the example of artificial selection to explain evolution. Members of a species varied, those that better suited their environment flourished, while others lacking such advantages did not. 

• In the same year, Charles Darwin’s grandfather, Erasmus Darwin, wrote a book called Zoonomia. He suggested that the strongest members of a species were more likely to survive. He also pushed for a common origin theory. But unlike his more lauded grandson, Erasmus Darwin’s ideas were speculative with little evidence to back them.  

Different Theories of Evolution 

• In 1809, Jean-Baptiste Lamarck put forth his theory of transmutation that came to be the strongest contender to Darwin’s theory of natural selection. Tussles between Lamarckism and Darwinism continue to date. According to Lamarck, all species did not share a common ancestor but some basic forms had been created spontaneously from which others had evolved. He did agree that species changed in response to their environment. Moreover, offspring inherited those changes that were most frequently enacted. These inheritable changes led to evolution of a species. 

• In 1844, Robert Chambers’ book Vestiges of the Natural History of Creation, was published. In it, he proposed theories on not only the origin of humans but also the solar system. He suggested humans were the last in a line of species that had evolved from a common ancestor.   

• Not long before Darwin and Wallace came into the picture, William Charles Wells had acknowledged the existence of natural selection—at least in humans. While Darwin had not come across Wells’ work, he later admitted that Wells’ had been the first to understand natural selection.  

While bits and pieces of Darwin’s theory had been worked on by other scientists, philosophers, and even clergymen over the years. But Darwin and Alfred Russell Wallace were the first to cohesively bring these different ideas together as well as back it with scientific evidence. Wallace had preceded Darwin with a set of papers on evolution but over time was pushed to the sidelines.  

What is Natural Selection in Evolution? 

In 1831, Charles Darwin, serving as a naturalist on the survey ship H.M.S. Beagle, set sail for Europe and South America. His journey around the continents, and particularly to the Galápagos Islands off the coast of Ecuador would provide compelling evidence for evolution.   

In the five years, while Darwin was aboard the ship, he often went on land to avoid the seasickness that plagued him on the high seas. He observed the flora and fauna of South America and Europe. He noted down the many differences between the creatures found on the two continents. Darwin also noticed the similarity between species from different biomes on the same landmass.  

For example, he found that the animals in the temperate zone of South America were more similar to those in the continent’s tropical zone compared to those in the temperate zone of Europe. He learned that different animals favored the various Galápagos Islands and seemed to have evolved independently on the islands. The species of animals on Galápagos also seemed similar to those found in South America. This raised the possibility that they may have diverged from animals on the mainland at some point in time. 

Darwin had found that species around the world appeared to have adapted to their specific environment. Thus, evolution seemed to be a product of the natural world. Creatures around the globe had been molded through adaptation to suit their surroundings. Darwin was of the opinion that individuals that could adapt to their environs survived. Those that couldn’t, grew sparse within a population, before eventually dying out. In this way, a population evolved as a whole. This process, Darwin called, natural selection.  

5 Ways to Describe Evidence for Evolution   

Darwin had proposed his theory in The Origin of Species. Born in 1904, Ernst Mayr, an evolutionary biologist, is known for his work on the definition of species. Mayr’s work on speciation was inspired by Darwin’s and brought modern evidence of evolution.  

In addition to this, he put forth his own spin on Darwin’s theory of evolution and natural selection.  

Mayr distilled it to five observations from which he inferred three aspects of evolution. 

Observation 1 

Generally, populations of organisms have high fertility rates. If they reproduced unabated, their population would rise uncontrollably. For instance, if one bacterium was to give rise to two bacteria, the bacterial population growth over time would be exponential—from one to two to four to eight and so on. In under a week, the progeny of a single Escherichia coli could weigh about as much as planet Earth.  

Here’s another example: oysters. These creatures can lay 114,000,000 eggs in one fell swoop. If all these eggs successfully matured into full-grown oysters who each went on to have as many eggs of their own that also all grew into adults, then five generations is all it would take for there to be more oysters than electrons in the universe. Clearly, oysters never produce enough offspring to make it to that mind-boggling figure.  

Thus, despite this innate ability of most species to furiously reproduce, in reality, there aren’t excessive numbers of them. Something keeps a check on those numbers. 

Observation 2

While theoretically, oysters and most creatures can multiply exponentially, the reality is quite different. The reason there aren’t hundreds of thousands of oysters in the oceans is that most of their offspring may not have their own opportunities to reproduce.  

Many a number of them will die from starvation, predation or infection. Outside of temporary ups and downs, population sizes tend to remain constant. Thus, even though an oyster produces 114,000,000 eggs, only a measly two of that number are likely to go on and reproduce successfully.  

Observation 3

Natural resources available to species are in short supply. The planet’s resources are limited.  

From these three observations, Mayr proposed the following.

• Mayr’s first inference 

As resources are constrained, a boom in the population can mean little to go around. Thus, only the number of individuals that can be supported by the environment will survive. Organisms need to compete with other members of their species. This struggle for resources means that only a small percentage of offspring will survive.  

According to Darwin, this struggle was not only between organisms belonging to a species but also between organisms and their environments. Thus, the environment was what kept the population numbers restrained. 

Observation 4

Despite belonging to the same species, members can be very different from each other. According to Darwin, these variations were the very lifeblood of evolution.  

Observation 5

Darwin also understood that family members tended to share some traits. Thus, variations in characteristics can be inherited.  

Darwin knew that both these principles were crucial for natural selection to occur. But, he could not justify the existence of variation and how traits are passed down. 

At the time of Darwin’s proposal, the study of genetics was nonexistent. DNA hadn’t been identified. Now, the molecular causes for variation are known. Random mutations and recombinations of genes result in new traits—be they helpful, harmful, or neutral. 

• Mayr’s second inference 

Using these two observations, Mayr explained that these differences between organisms belonging to the same species influenced the likelihood of their survival. Individuals who were most suited for their environment were more likely to succeed. These members were also more likely to leave behind greater numbers of progeny.

• Mayr’s third inference 

From two of his inferences, Mayr drew his final conclusion about Darwin’s theory.

1. Most species would overproduce were it not for environmental pressures.  
2. Individuals of the same species display different traits that passed from parent to progeny.
3. Such individuals will produce more offspring than those with deficient traits will produce.  

While these beneficial traits arise in a random fashion, their distribution among the population is anything but random. This is because organisms within a population with favorable characteristics are selected for survival. 

The struggle for survival is not based purely on chance. While good traits arise randomly, their distribution in the new generation is non-random—provided the trait is needed for reproduction and the very existence of the organism.  

Inherited traits possessed by some individuals of a species that make them better fit for the environment would win out over other less beneficial traits. This inequality of reproductive success across a species is not random. It will eventually result in a population with beneficial characteristics.  

Thus, populations evolve as a whole, not individuals alone. 

Conclusion 

A modern lens on natural selection and evolution creates some interesting questions.  

While each and every observation and inference has been experimentally established, neither can drive evolution alone. If all the numerous individuals belonging to a species were similar and variation were not inherited, natural selection would not be enforced. 

On the other hand, natural selection will almost always occur provided all of Darwin’s proposals are met. As a result, favored genes are passed to the offspring at a higher frequency than unfavorable traits.  

This unequal split up among the population is repeated with every generation and its effect is aggregated over several rounds of reproduction. Better and better traits will grow in a population as parents possessing them to leave behind more children.  

In this way, the population gradually changes to reflect beneficial traits. While the organism may be changing, it is the population that evolves. 

We will be discussing evolution further in respects to advances in the epigenetics of natural selection and quantum biology.   

Now it’s up to you. 

Do you think Ernst Mayr’s observations provide evidence for evolution? Leave your thoughts in the comment section below.  

Further reading:  

• https://link.springer.com/article/10.1007/s12052-009-0128-1 
• https://www.amazon.com/Life-Science-William-K-Purves/dp/0716798565  
• https://www.scientificamerican.com/article/the-evolution-of-ernst-in/
• https://early-evolution.oeb.harvard.edu/

The post New Human Evidence of Evolution & Darwin’s Theory [In 5 Easy Points] appeared first on .

Your genome tells the stories of how your ancestors evolved. DNA discovered in fossil records is constantly changing the story of this human evolution.  

Research has suggested modern humans living outside of Africa have between 1 and 4 percent of Neanderthal DNA.  

How and when did Neanderthal DNA wind up in the modern human’s genome? Scientists have been trying to establish a time and place for such an interaction between humans and Neanderthals.  

Lately, the evidence has grown with multiple instances of interbreeding between the two species having been found.  

Let’s go back in time look at the story of Neanderthal DNA. 

 What is Neanderthal Man? 

Image: Neanderthal Man as featured in Mettmann Museum near Düsseldorf. Photo: Don Hitchcock 2015

In 1857, Hermann Schaafhausen, a German anatomist, presented his findings on the Neanderthal man (Homo neanderthalis). Prussian workers cutting limestone in the Neander valley of Germany found its bones inside a cave in 1856.  

Named after the Neander valley, this set of Neanderthal bones were not the first to be found. In 1829, similar bones had been discovered, but at the time researchers had been unable to classify them. 

Neanderthal man lived across Europe and parts of Asia. Some archaeological remains have been found as far east as Russia. They are thought to have lived between 400,000 and 40,000 years ago.  

Recent research has implied that Neanderthals crossed paths with humans at multiple points across space and time.  

As scientists look back at Neanderthal man, their theories about his evolution, interaction with modern man and eventual extinction continue to develop.

What is the difference between Neanderthals and humans? 

Image: Original recraction of Neanderthal Man, by Atelier Manufaktur, München. Photo: Don Hitchcock 2015 Reference

Neanderthal characteristics are humanoid in nature. Their standout features include a heavy brow, large nose, angular cheekbones, short stature, and often, a larger brain case when compared to a human. Whereas, modern humans are said to have smaller brains and skulls,  and smaller noses than Neanderthals.  

Also, the Neanderthals were likely much stronger than modern human species or Homo sapiens. Researchers believe they were especially adapted to withstand the harsh winters of the north. While Neanderthals were hunter-gatherers, H. sapiens live a settled life, producing food through agriculture and domestication.

When was the last Neanderthal alive?

Image: Skull characteristics of a Neanderthal head and face. Source: Wikimedia Commons

Neanderthals disappeared from the planet 40,000 odd years ago. In the past, scientists have implicated infiltrating humans, their diseases and possibly murderous tendencies. While many theories for why Neanderthals died out exist, the latest places the blame on climate change. Environmental disasters had been proposed as a cause in the past. 

Why did Neanderthals go extinct? 

Recently studies have reported that two back-to-back cold spells were the straw that broke the camel’s back. A 1000-year long cold period around 44,000 years ago and another 600-year long spell about 40,800 years ago may have driven the Neanderthals to extinction. The year-round permafrost may have been the final shove for the already-declining species. 

Archaeological records corresponding to these cold spells suggest the Neanderthals were dying off. This, at the same time when early humans were advancing out of Africa and encroaching on Neanderthal territory.  

Previously, Neanderthals were believed to have become extinct 30,000 years ago. Early humans entered Europe 45,000 years ago. Thus, scientists entertained the idea that modern humans may have decimated Neanderthal man during those 15,000 overlapping years.  

New research suggests that Neanderthals reached extinction 40,000 years ago.  

The short time span between the advent of one species and departure of the other suggests something besides an all-out war may have been responsible for Neanderthal extinction. Modern humans’ adaptability may have helped them beat out the Neanderthals when it came to lasting through the cold. 

The Neanderthal DNA Project 

Established in 2006 at the Max Planck Institute for Evolutionary Anthropology, the Neanderthal genome project put forth its first draft of the Neanderthal genome in 2009. While this initial report suggested no genetic overlap between modern humans and Neanderthals, the project published a new set of results that contradicted the previous study.  

The study, which came out in 2010, found that modern-day Europeans and Asians—but not Africans—carried Neanderthal DNA. On the other hand, another study found that the Neanderthals did not seem to have gained genetically from their interactions with humans.

Does modern man have Neanderthal DNA?  

Yes! As Neanderthals may have mated (multiple times, even!) with humans, modern humans carry a small amount of Neanderthal DNA. Since the sequencing of the first complete Neanderthal genome in 2010, researchers have known that Neanderthals mixed with modern humans.  

While humans living in Europe and Asia today have low amounts of Neanderthal DNA, Africans do not. These low levels suggest that modern humans and Neanderthals met but a few times and only outside Africa. These encounters possibly happened in the Middle East or Arabian Peninsula soon after modern humans moved out of Africa. 

What percentage of DNA do humans share with Neanderthals? 

Between one percent and four percent of DNA belonging to Europeans and East Asians bears surprising resemblance to that of Neanderthals. Moreover, the various snippets of Neanderthal DNA that have been found in modern humans adds up to about 20 percent of the complete Neanderthal genome. But no one human is likely to showcase all 20 percent. 

There are some interesting traits Neanderthal DNA could play a role in for humans today. 

• Stretches of overlapping DNA are often found in genes that confer traits pertaining to skin or hair. 

• Certain genetic mutations known to make individuals more likely to become addicted to smoking have also been noticed.   

• Studies have also found Neanderthal traits in genes that alter one’s risk of developing lupus, biliary cirrhosis, Crohn’s disease, and type 2 diabetes.  

• These traits may once have proved useful in the environment Neanderthals evolved. For example, the mutation for type 2 diabetes may have helped abate starvation during Neanderthal times.  

Neanderthal traits also helped enhanced the immune system. 

Researchers suggest the Neanderthal copies of these genes may have been retained as they were beneficial. As humans colonized lands that had once served the Neanderthals, the latter’s adaptations may have proved useful to the former. This likely explains why certain Neanderthal genes were maintained in the genomes of modern humans. 

How long did Neanderthals and humans coexist? 

It is increasingly understood that modern humans may have come into contact with Neanderthals. Previously, researchers have believed that modern humans, leaving Africa, may have wiped out Neanderthals.  

Some believe that humans would have brought with them unique germs to which the Neanderthals may have lacked immunity. Others are of the opinion that humans may have waged many a battle against Neanderthal man.  

However, recent evidence has challenged the likelihood that humans and Neanderthals may not have gotten along during their interactions. They may have gotten along all too well. 

In 2010, evidence of Neanderthal DNA in present-day humans was first found. Scientists used Neanderthal remains found in Croatia to draft their first complete genome.  

Next, they compared the genomes of non-Africans and Neanderthals to help establish whether sexual relations occurred between them.  

Indeed, such interactions were reflected in the genome overlaps between the two kinds. The two species may have come across each other in the Middle East around 50,000 to 60,000 years ago and mated.

Could Neanderthals and humans have reproduced? 

More recent evidence strengthens the likelihood of such relationships between humans and Neanderthals. A 45,000-year old Romanian human skeleton may have had a Neanderthal great-great grandparent. This interaction was likely to have occurred between 50,000 and 65,000 years ago.  

Some researchers are also of the opinion that the ancestors of East Asians may have mingled with Neanderthals a second time, making them more mixed than Europeans.  

On the other side of things, the genome of a female Neanderthal has been found to contain bits and pieces of H. sapiens DNA. These may have appeared due to encounters between the two species in the Middle East.

A recent study takes this connection between humans and Neanderthals even further back. The more than 50,000-year old toe bone of a Neanderthal woman was found to have the DNA of an early modern human. The latter do not seem to be represented among the current human population.  

These results push back the dates of interactions between the two groups thousands of years back. The researchers suggest that Neanderthals migrating from Europe to Asia may have bumped into an early wave of H. sapiens heading out of Africa.  

Thus, humans and Neanderthals seem to have met and mated at multiple spots around the world. New studies help to clarify the extent of these encounters between Neanderthal and modern man.

Is red hair a Neanderthal gene? 

Despite what you may have heard, your red-headed friend may not owe their trait to possible Neanderthal DNA. Though they may be able to attribute their height or hairy back to it. The genetic testing company, 23andMe, can now tell you the functions of some of the Neanderthal genetic mutations you have. 

While Neanderthals possessed red hair, the mutation that is responsible for their hair colour is not present in modern humans. Present-day humans with red hair have a different mutation in the same gene. So, modern humans with red hair do not owe their Neanderthalic roots for this feature. 

Are Neanderthal humans? 

At the time of Schaafhausen’s report, confusion reigned about the finding. Superficially, the remains looked quite human. When studied in greater depth, the bones revealed difference that set them apart from a modern human’s skeleton.  

So, did the bones belong to the human species or a different one altogether? While significant progress has been made in the study of Neanderthals over the past 150 years, this question still encourages debate.  

The Neanderthal man is classified in the same genus, Homo, as modern humans. But not everyone agrees that this is how it should be. According to the classical definition of a species, reproduction between two species—if possible—will result in the birth of sterile progeny.  

Archaeological and genomic studies have revealed the presence, albeit minimal, of Neanderthal DNA in today’s humans. This suggests that encounters between the Neanderthals and humans were successful and led to fertile offspring, at least sometimes.  

But, this raises questions about the segregation of Neanderthals and humans into separate species. It also throws the very definition of species into doubt. Thus, scientists continue to debate about the classification of Neanderthals.

Conclusion

Neanderthal man walked the planet thousands of years ago. Researchers had always wondered if modern man’s meeting with Neanderthals led to their extinction. Whether this occurred is still unknown.  

We do know that modern man met Neanderthal man several times over the course of thousands of years. Often these meetings resulted in matings that sometimes led to fertile offspring.  

These matings seem to have occurred across vast expanses but still early on in modern man’s history. This possibly explains why non-African humans have but a small amount of Neanderthal DNA.  

Over the years, through the exchange of genetic material, certain Neanderthal genes have been retained in modern humans. While some are beneficial to us, others increase our risk of several diseases. Researchers are not quite certain if modern man left an impact on Neanderthals but the species certainly left its mark on us.  

Now it’s up to you. What do you think Neanderthal DNA tells us about human origins?

Further reading: 

• https://www.smithsonianmag.com/smart-news/modern-humans-didnt-kill-neanderthals-weather-did-180970167/ 
  https://www.the-scientist.com/daily-news/effects-of-neanderthal-dna-on-modern-humans-30787 
• https://www.pbs.org/wgbh/nova/article/are-neanderthals-human/ 
• https://www.nature.com/news/evidence-mounts-for-interbreeding-bonanza-in-ancient-human-species-1.19394  
• https://www.sciencemag.org/news/2016/02/humans-mated-neandertals-much-earlier-and-more-frequently-thought?r3f_986
• https://news.nationalgeographic.com/news/2014/01/140129-neanderthal-genes-genetics-migration-africa-eurasian-science/ 
• https://www.genome.gov/27539119/2010-release-complete-neanderthal-genome-sequenced/  

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