Are humans domesticated animals?

If the neural crest hypothesis is correct, humans are the first domesticated animals. But who, or what, tamed us?

Animal husbandry is perhaps 30,000 years old, starting with the humble dog. Several species came afterward and domestication was born. What most people may not know is that there’s one species that became domesticated even before the dog, and that’s us. But to understand why, we need to know the nuances of the various definitions of domestication and where they come from. Domestication is generally defined as the purposeful breeding of a plant or animal for human benefit. But science looks at it a tad differently.

The science of domestication

Domestication syndrome is the physical traits that occur to a wild plant or animal as it becomes domesticated. For mammals this includes things like floppy ears, shorter muzzles, curly tails, white hair—particularly prominent in dogs, cats, and rabbits, and lighter colored coats. Other physical characteristics include smaller brains, shorter limbs, and smaller teeth. There are changes in personality too which include sociability, tameness, and even juvenile behavior.

Darwin first noticed this not among the unique species of the Galapagos but in the common pigeon along the Thames and how much it differed from the fancier varieties Londoners kept as pets. Those beautiful, compliant ceremonial doves? They're actually just white pigeons. He likened the differences to the kept bird’s better diet, comfier living conditions, and its ability to interbreed with other domesticated birds, leading to hybridization. Humans and animals entirely similar in the respect that each is shaped by the environmental circumstances thrust upon them.

Is it diet, breeding, and a cushier lifestyle that causes domestication, or something more? Credit: Getty Images.

The Soviet experiment

In 1959, Soviet geneticist Dmitry Belyaev began breeding wild foxes to study how they became domesticated over time. He took the most social ones and mated them. Over 10 generations, Belyaev witnessed a dramatic change in them. Personality wise, the foxes became more sociable and playful over time. Physically, they began to have floppier ears, smaller skulls, and patches of white fur in their coats. The males also started to more closely resemble females. What he had found was that domesticated mammals who spent a lot of time with humans and were bred for sociability over generations exhibited similar traits.

This discovery of domestication syndrome didn’t just focus the lens on animals but back onto us as well. Our jaws are small and rounded, our brains smaller than that of the Neanderthal—one of our closest (though extinct) ancestors. At the time, being a discomforting thought with little hard evidence to support it, the idea that humans are also in a way domesticated was lost, mostly, because it was hard to test.

Since that time, a combination of advancements in genetics, our understanding of human evolution, and a number of important paleontological discoveries have led to greater insight into our own species’ development. This, in turn, had led to a recognition of this strange phenomenon and once again thrust it into the spotlight. In 2014, an international team of scientists made a discovery that changed the way we look at domestication and human evolution dramatically.

The neural crest cell hypothesis

Richard Wrangham of Harvard, Adam Wilkins, now at Humboldt University in Germany, and Tecumseh Fitch at the University of Vienna, Austria, came up with what’s known as the neural crest cell hypothesis. Together, they found what connects all of the traits associated with domestication including changes to the teeth, ears, skin, and temperament. They all originate in the neural crest.

Figure 1: Developmental schematic of the “domestication syndrome” in relation to the neural crest. The blue tube indicates the approximate position of the neural crest in the early embryo, and the blue arrows indicate pathways of neural crest cell migration. (Credit: Adam S. WilkinsRichard W. Wrangham and W. Tecumseh Fitch)

The neural crest is a congregation of cells that forms in a developing embryo. This tiny mass eventually breaks up and becomes different tissues in the body, including the adrenal glands—responsible for the stress response (and in a way, temperament), cartilage in the ears, melanocyte cells which create the skin’s pigment, and dentin which forms the teeth. They also earmarked dozens of genes associated with domestication, each one linking back to the neural crest.

Researchers could then compare domestication genes with those found in the genomes of an animal's wild counterpart. Surprisingly, the genetic changes that caused domestication were the same across all mammalian species, whether it be from wolves to dogs, European bison to cattle, or Neanderthals to humans. The genetic changes that drove these transitions were identical. 

So if humans domesticated other species, who or what domesticated us?

If we look at human domestication as changes that allowed us to work and live together to survive, you can say evolution tamed us. Around 100,000 years ago, our species began living closer together. It would’ve been better to cooperate with new neighbors than fight them. Around that same time, the pronounced brow ridges and long faces humans once had were being replaced by smoother, softer, more feminine features.

Scientists believe that the same forces which helped shape domestic animals also affected us. Credit: Getty Images.

One theory is that when our bodies and brains grew bigger, we became less aggressive. Larger animals with bigger brains tend to act more peaceably. This is domestication through natural selection. Those humans who were less aggressive and more cooperative were more likely to pass on their genes, and so these traits became a signature part of our species. Then, interacting with other species over time molded them in the same way. Keep in mind that this is all very new to science and more research must be done to better understand the phenomenon.

To learn more about domestication, click here.

Related Articles

Why "nuclear pasta" is the strongest material in the universe

Through computationally intensive computer simulations, researchers have discovered that "nuclear pasta," found in the crusts of neutron stars, is the strongest material in the universe.

Accretion disk surrounding a neutron star. Credit: NASA
Surprising Science
  • The strongest material in the universe may be the whimsically named "nuclear pasta."
  • You can find this substance in the crust of neutron stars.
  • This amazing material is super-dense, and is 10 billion times harder to break than steel.

Superman is known as the "Man of Steel" for his strength and indestructibility. But the discovery of a new material that's 10 billion times harder to break than steel begs the question—is it time for a new superhero known as "Nuclear Pasta"? That's the name of the substance that a team of researchers thinks is the strongest known material in the universe.

Unlike humans, when stars reach a certain age, they do not just wither and die, but they explode, collapsing into a mass of neurons. The resulting space entity, known as a neutron star, is incredibly dense. So much so that previous research showed that the surface of a such a star would feature amazingly strong material. The new research, which involved the largest-ever computer simulations of a neutron star's crust, proposes that "nuclear pasta," the material just under the surface, is actually stronger.

The competition between forces from protons and neutrons inside a neutron star create super-dense shapes that look like long cylinders or flat planes, referred to as "spaghetti" and "lasagna," respectively. That's also where we get the overall name of nuclear pasta.

Caplan & Horowitz/arXiv

Diagrams illustrating the different types of so-called nuclear pasta.

The researchers' computer simulations needed 2 million hours of processor time before completion, which would be, according to a press release from McGill University, "the equivalent of 250 years on a laptop with a single good GPU." Fortunately, the researchers had access to a supercomputer, although it still took a couple of years. The scientists' simulations consisted of stretching and deforming the nuclear pasta to see how it behaved and what it would take to break it.

While they were able to discover just how strong nuclear pasta seems to be, no one is holding their breath that we'll be sending out missions to mine this substance any time soon. Instead, the discovery has other significant applications.

One of the study's co-authors, Matthew Caplan, a postdoctoral research fellow at McGill University, said the neutron stars would be "a hundred trillion times denser than anything on earth." Understanding what's inside them would be valuable for astronomers because now only the outer layer of such starts can be observed.

"A lot of interesting physics is going on here under extreme conditions and so understanding the physical properties of a neutron star is a way for scientists to test their theories and models," Caplan added. "With this result, many problems need to be revisited. How large a mountain can you build on a neutron star before the crust breaks and it collapses? What will it look like? And most importantly, how can astronomers observe it?"

Another possibility worth studying is that, due to its instability, nuclear pasta might generate gravitational waves. It may be possible to observe them at some point here on Earth by utilizing very sensitive equipment.

The team of scientists also included A. S. Schneider from California Institute of Technology and C. J. Horowitz from Indiana University.

Check out the study "The elasticity of nuclear pasta," published in Physical Review Letters.

How a huge, underwater wall could save melting Antarctic glaciers

Scientists think constructing a miles-long wall along an ice shelf in Antarctica could help protect the world's largest glacier from melting.

Image: NASA
Surprising Science
  • Rising ocean levels are a serious threat to coastal regions around the globe.
  • Scientists have proposed large-scale geoengineering projects that would prevent ice shelves from melting.
  • The most successful solution proposed would be a miles-long, incredibly tall underwater wall at the edge of the ice shelves.

The world's oceans will rise significantly over the next century if the massive ice shelves connected to Antarctica begin to fail as a result of global warming.

To prevent or hold off such a catastrophe, a team of scientists recently proposed a radical plan: build underwater walls that would either support the ice or protect it from warm waters.

In a paper published in The Cryosphere, Michael Wolovick and John Moore from Princeton and the Beijing Normal University, respectively, outlined several "targeted geoengineering" solutions that could help prevent the melting of western Antarctica's Florida-sized Thwaites Glacier, whose melting waters are projected to be the largest source of sea-level rise in the foreseeable future.

An "unthinkable" engineering project

"If [glacial geoengineering] works there then we would expect it to work on less challenging glaciers as well," the authors wrote in the study.

One approach involves using sand or gravel to build artificial mounds on the seafloor that would help support the glacier and hopefully allow it to regrow. In another strategy, an underwater wall would be built to prevent warm waters from eating away at the glacier's base.

The most effective design, according to the team's computer simulations, would be a miles-long and very tall wall, or "artificial sill," that serves as a "continuous barrier" across the length of the glacier, providing it both physical support and protection from warm waters. Although the study authors suggested this option is currently beyond any engineering feat humans have attempted, it was shown to be the most effective solution in preventing the glacier from collapsing.

Source: Wolovick et al.

An example of the proposed geoengineering project. By blocking off the warm water that would otherwise eat away at the glacier's base, further sea level rise might be preventable.

But other, more feasible options could also be effective. For example, building a smaller wall that blocks about 50% of warm water from reaching the glacier would have about a 70% chance of preventing a runaway collapse, while constructing a series of isolated, 1,000-foot-tall columns on the seafloor as supports had about a 30% chance of success.

Still, the authors note that the frigid waters of the Antarctica present unprecedently challenging conditions for such an ambitious geoengineering project. They were also sure to caution that their encouraging results shouldn't be seen as reasons to neglect other measures that would cut global emissions or otherwise combat climate change.

"There are dishonest elements of society that will try to use our research to argue against the necessity of emissions' reductions. Our research does not in any way support that interpretation," they wrote.

"The more carbon we emit, the less likely it becomes that the ice sheets will survive in the long term at anything close to their present volume."

A 2015 report from the National Academies of Sciences, Engineering, and Medicine illustrates the potentially devastating effects of ice-shelf melting in western Antarctica.

"As the oceans and atmosphere warm, melting of ice shelves in key areas around the edges of the Antarctic ice sheet could trigger a runaway collapse process known as Marine Ice Sheet Instability. If this were to occur, the collapse of the West Antarctic Ice Sheet (WAIS) could potentially contribute 2 to 4 meters (6.5 to 13 feet) of global sea level rise within just a few centuries."

Why the worst part about climate change isn't rising temperatures

The world's getting hotter, and it's getting more volatile. We need to start thinking about how climate change encourages conflict.

Christopher Furlong/Getty Images
Politics & Current Affairs
  • Climate change is usually discussed in terms of how it impacts the weather, but this fails to emphasize how climate change is a "threat multiplier."
  • As a threat multiplier, climate change makes already dangerous social and political situations even worse.
  • Not only do we have to work to minimize the impact of climate change on our environment, but we also have to deal with how it affects human issues today.

Human beings are great at responding to imminent and visible threats. Climate change, while dire, is almost entirely the opposite: it's slow, it's pervasive, it's vague, and it's invisible. Researchers and policymakers have been trying to package climate change in a way that conveys its severity. Usually, they do so by talking about its immediate effects: rising temperature, rising sea levels, and increasingly dangerous weather.

These things are bad, make no mistake about it. But the thing that makes climate change truly dire isn't that Cape Cod will be underwater next century, that polar bears will go extinct, or that we'll have to invent new categories for future hurricanes. It's the thousands of ancillary effects — the indirect pressure that climate change puts on every person on the planet.

How a drought in the Middle East contributed to extremism in Europe


Nigel Farage in front of a billboard that leverages the immigration crisis to support Brexit.

Because climate change is too big for the mind to grasp, we'll have to use a case study to talk about this. The Syrian civil war is a horrific tangle of senseless violence, but there are some primary causes we can point to. There is the longstanding conflicts between different religious sects in that country. Additionally, the Arab Spring swept Syria up in a wave of resistance against authoritarian leaders in the Middle East — unfortunately, Syrian protests were brutally squashed by Bashar Al-Assad. These, and many other factors, contributed to the start of the Syrian civil war.

One of these other factors was drought. In fact, the drought in that region — it started in 2006 — has been described as the "worst long-term drought and most severe set of crop failures since agricultural civilization began in the Fertile Crescent many millennia ago." Because of this drought, many rural Syrians could no longer support themselves. Between 2006 and 2009, an estimated 1.5 million Syrians — many of them agricultural workers and farmers — moved into the country's major cities. With this sudden mixing of different social groups in a country where classes and religious sects were already at odds with one another, tensions rose, and the increased economic instability encouraged chaos. Again, the drought didn't cause the civil war — but it sure as hell helped it along.

The ensuing flood of refugees to Europe is already a well-known story. The immigration crisis was used as a talking point in the Brexit movement to encourage Britain to leave the EU. Authoritarian or extreme-right governments and political parties have sprung up in France, Italy, Greece, Hungary, Slovenia, and other European countries, all of which have capitalized on fears of the immigration crisis.

Why climate change is a "threat multiplier"

This is why both NATO and the Pentagon have labeled climate change as a "threat multiplier." On its own, climate change doesn't cause these issues — rather, it exacerbates underlying problems in societies around the world. Think of having a heated discussion inside a slowly heating-up car.

Climate change is often discussed in terms of its domino effect: for example, higher temperatures around the world melt the icecaps, releasing methane stored in the polar ice that contributes to the rise in temperature, which both reduces available land for agriculture due to drought and makes parts of the ocean uninhabitable for different animal species, wreaking havoc on the food chain, and ultimately making food more scarce.

Maybe we should start to consider climate change's domino effect in more human and political terms. That is, in terms of the dominoes of sociopolitical events spurred on by climate change and the missing resources it gobbles up.

What the future may hold

(NASA via Getty Images)

Increasingly severe weather events will make it more difficult for nations to avoid conflict.

Part of why this is difficult to see is because climate change does not affect all countries proportionally — at least, not in a direct sense. Germanwatch, a German NGO, releases a climate change index every year to analyze exactly how badly different countries have been affected by climate change. The top five most at-risk countries are Haiti, Zimbabwe, Fiji, Sri Lanka, and Vietnam. Notice that many of these places are islands, which are at the greatest risk for major storms and rising sea levels. Some island nations are even expected to literally disappear — the leaders of these nations are actively making plans to move their citizens to other countries.

But Germanwatch's climate change index is based on weather events. It does not account for the political and social instability that will likely result. The U.S. and many parts of Europe are relatively low on the index, but that is precisely why these countries will most likely need to deal with the human cost of climate change. Refugees won't go from the frying pan into the fire: they'll go to the closest, safest place available.

Many people's instinctive response to floods of immigrants is to simply make borders more restrictive. This makes sense — a nation's first duty is to its own citizens, after all. Unfortunately, people who support stronger immigration policies tend to have right-wing authoritarian tendencies. This isn't always the case, of course, but anecdotally, we can look at the governments in Europe that have stricter immigration policies. Hungary, for example, has extremely strict policies against Muslim immigrants. It's also rapidly turning into a dictatorship. The country has cracked down on media organizations and NGOs, eroded its judicial system's independence, illegalized homelessness, and banned gender studies courses.

Climate change and its sociopolitical effects, such as refugee migration, aren't some poorer country's problem. It's everyone's problem. Whether it's our food, our homes, or our rights, climate change will exact a toll on every nation on Earth. Stopping climate change, or at least reducing its impact, is vitally important. Equally important is contending with the multifaceted threats its going to throw our way.