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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.
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.
Geologists discover a rhythm to major geologic events.
- It appears that Earth has a geologic "pulse," with clusters of major events occurring every 27.5 million years.
- Working with the most accurate dating methods available, the authors of the study constructed a new history of the last 260 million years.
- Exactly why these cycles occur remains unknown, but there are some interesting theories.
Our hearts beat at a resting rate of 60 to 100 beats per minute. Lots of other things pulse, too. The colors we see and the pitches we hear, for example, are due to the different wave frequencies ("pulses") of light and sound waves.
Now, a study in the journal Geoscience Frontiers finds that Earth itself has a pulse, with one "beat" every 27.5 million years. That's the rate at which major geological events have been occurring as far back as geologists can tell.
A planetary calendar has 10 dates in red
Credit: Jagoush / Adobe Stock
According to lead author and geologist Michael Rampino of New York University's Department of Biology, "Many geologists believe that geological events are random over time. But our study provides statistical evidence for a common cycle, suggesting that these geologic events are correlated and not random."
The new study is not the first time that there's been a suggestion of a planetary geologic cycle, but it's only with recent refinements in radioisotopic dating techniques that there's evidence supporting the theory. The authors of the study collected the latest, best dating for 89 known geologic events over the last 260 million years:
- 29 sea level fluctuations
- 12 marine extinctions
- 9 land-based extinctions
- 10 periods of low ocean oxygenation
- 13 gigantic flood basalt volcanic eruptions
- 8 changes in the rate of seafloor spread
- 8 times there were global pulsations in interplate magmatism
The dates provided the scientists a new timetable of Earth's geologic history.
Tick, tick, boom
Credit: New York University
Putting all the events together, the scientists performed a series of statistical analyses that revealed that events tend to cluster around 10 different dates, with peak activity occurring every 27.5 million years. Between the ten busy periods, the number of events dropped sharply, approaching zero.
Perhaps the most fascinating question that remains unanswered for now is exactly why this is happening. The authors of the study suggest two possibilities:
"The correlations and cyclicity seen in the geologic episodes may be entirely a function of global internal Earth dynamics affecting global tectonics and climate, but similar cycles in the Earth's orbit in the Solar System and in the Galaxy might be pacing these events. Whatever the origins of these cyclical episodes, their occurrences support the case for a largely periodic, coordinated, and intermittently catastrophic geologic record, which is quite different from the views held by most geologists."
Assuming the researchers' calculations are at least roughly correct — the authors note that different statistical formulas may result in further refinement of their conclusions — there's no need to worry that we're about to be thumped by another planetary heartbeat. The last occurred some seven million years ago, meaning the next won't happen for about another 20 million years.
Research shows that those who spend more time speaking tend to emerge as the leaders of groups, regardless of their intelligence.
If you want to become a leader, start yammering. It doesn't even necessarily matter what you say. New research shows that groups without a leader can find one if somebody starts talking a lot.
This phenomenon, described by the "babble hypothesis" of leadership, depends neither on group member intelligence nor personality. Leaders emerge based on the quantity of speaking, not quality.
Researcher Neil G. MacLaren, lead author of the study published in The Leadership Quarterly, believes his team's work may improve how groups are organized and how individuals within them are trained and evaluated.
"It turns out that early attempts to assess leadership quality were found to be highly confounded with a simple quantity: the amount of time that group members spoke during a discussion," shared MacLaren, who is a research fellow at Binghamton University.
While we tend to think of leaders as people who share important ideas, leadership may boil down to whoever "babbles" the most. Understanding the connection between how much people speak and how they become perceived as leaders is key to growing our knowledge of group dynamics.
The power of babble
The research involved 256 college students, divided into 33 groups of four to ten people each. They were asked to collaborate on either a military computer simulation game (BCT Commander) or a business-oriented game (CleanStart). The players had ten minutes to plan how they would carry out a task and 60 minutes to accomplish it as a group. One person in the group was randomly designated as the "operator," whose job was to control the user interface of the game.
To determine who became the leader of each group, the researchers asked the participants both before and after the game to nominate one to five people for this distinction. The scientists found that those who talked more were also more likely to be nominated. This remained true after controlling for a number of variables, such as previous knowledge of the game, various personality traits, or intelligence.
How leaders influence people to believe | Michael Dowling | Big Think www.youtube.com
In an interview with PsyPost, MacLaren shared that "the evidence does seem consistent that people who speak more are more likely to be viewed as leaders."
Another find was that gender bias seemed to have a strong effect on who was considered a leader. "In our data, men receive on average an extra vote just for being a man," explained MacLaren. "The effect is more extreme for the individual with the most votes."
The great theoretical physicist Steven Weinberg passed away on July 23. This is our tribute.
- The recent passing of the great theoretical physicist Steven Weinberg brought back memories of how his book got me into the study of cosmology.
- Going back in time, toward the cosmic infancy, is a spectacular effort that combines experimental and theoretical ingenuity. Modern cosmology is an experimental science.
- The cosmic story is, ultimately, our own. Our roots reach down to the earliest moments after creation.
When I was a junior in college, my electromagnetism professor had an awesome idea. Apart from the usual homework and exams, we were to give a seminar to the class on a topic of our choosing. The idea was to gauge which area of physics we would be interested in following professionally.
Professor Gilson Carneiro knew I was interested in cosmology and suggested a book by Nobel Prize Laureate Steven Weinberg: The First Three Minutes: A Modern View of the Origin of the Universe. I still have my original copy in Portuguese, from 1979, that emanates a musty tropical smell, sitting on my bookshelf side-by-side with the American version, a Bantam edition from 1979.
Inspired by Steven Weinberg
Books can change lives. They can illuminate the path ahead. In my case, there is no question that Weinberg's book blew my teenage mind. I decided, then and there, that I would become a cosmologist working on the physics of the early universe. The first three minutes of cosmic existence — what could be more exciting for a young physicist than trying to uncover the mystery of creation itself and the origin of the universe, matter, and stars? Weinberg quickly became my modern physics hero, the one I wanted to emulate professionally. Sadly, he passed away July 23rd, leaving a huge void for a generation of physicists.
What excited my young imagination was that science could actually make sense of the very early universe, meaning that theories could be validated and ideas could be tested against real data. Cosmology, as a science, only really took off after Einstein published his paper on the shape of the universe in 1917, two years after his groundbreaking paper on the theory of general relativity, the one explaining how we can interpret gravity as the curvature of spacetime. Matter doesn't "bend" time, but it affects how quickly it flows. (See last week's essay on what happens when you fall into a black hole).
The Big Bang Theory
For most of the 20th century, cosmology lived in the realm of theoretical speculation. One model proposed that the universe started from a small, hot, dense plasma billions of years ago and has been expanding ever since — the Big Bang model; another suggested that the cosmos stands still and that the changes astronomers see are mostly local — the steady state model.
Competing models are essential to science but so is data to help us discriminate among them. In the mid 1960s, a decisive discovery changed the game forever. Arno Penzias and Robert Wilson accidentally discovered the cosmic microwave background radiation (CMB), a fossil from the early universe predicted to exist by George Gamow, Ralph Alpher, and Robert Herman in their Big Bang model. (Alpher and Herman published a lovely account of the history here.) The CMB is a bath of microwave photons that permeates the whole of space, a remnant from the epoch when the first hydrogen atoms were forged, some 400,000 years after the bang.
The existence of the CMB was the smoking gun confirming the Big Bang model. From that moment on, a series of spectacular observatories and detectors, both on land and in space, have extracted huge amounts of information from the properties of the CMB, a bit like paleontologists that excavate the remains of dinosaurs and dig for more bones to get details of a past long gone.
How far back can we go?
Confirming the general outline of the Big Bang model changed our cosmic view. The universe, like you and me, has a history, a past waiting to be explored. How far back in time could we dig? Was there some ultimate wall we cannot pass?
Because matter gets hot as it gets squeezed, going back in time meant looking at matter and radiation at higher and higher temperatures. There is a simple relation that connects the age of the universe and its temperature, measured in terms of the temperature of photons (the particles of visible light and other forms of invisible radiation). The fun thing is that matter breaks down as the temperature increases. So, going back in time means looking at matter at more and more primitive states of organization. After the CMB formed 400,000 years after the bang, there were hydrogen atoms. Before, there weren't. The universe was filled with a primordial soup of particles: protons, neutrons, electrons, photons, and neutrinos, the ghostly particles that cross planets and people unscathed. Also, there were very light atomic nuclei, such as deuterium and tritium (both heavier cousins of hydrogen), helium, and lithium.
So, to study the universe after 400,000 years, we need to use atomic physics, at least until large clumps of matter aggregate due to gravity and start to collapse to form the first stars, a few millions of years after. What about earlier on? The cosmic history is broken down into chunks of time, each the realm of different kinds of physics. Before atoms form, all the way to about a second after the Big Bang, it's nuclear physics time. That's why Weinberg brilliantly titled his book The First Three Minutes. It is during the interval between one-hundredth of a second and three minutes that the light atomic nuclei (made of protons and neutrons) formed, a process called, with poetic flair, primordial nucleosynthesis. Protons collided with neutrons and, sometimes, stuck together due to the attractive strong nuclear force. Why did only a few light nuclei form then? Because the expansion of the universe made it hard for the particles to find each other.
What about the nuclei of heavier elements, like carbon, oxygen, calcium, gold? The answer is beautiful: all the elements of the periodic table after lithium were made and continue to be made in stars, the true cosmic alchemists. Hydrogen eventually becomes people if you wait long enough. At least in this universe.
In this article, we got all the way up to nucleosynthesis, the forging of the first atomic nuclei when the universe was a minute old. What about earlier on? How close to the beginning, to t = 0, can science get? Stay tuned, and we will continue next week.
To Steven Weinberg, with gratitude, for all that you taught us about the universe.
Long before Alexandria became the center of Egyptian trade, there was Thônis-Heracleion. But then it sank.