Changes made by living with humans in animals

About 8000 years ago, Southeast Asian nomads began breeding the Banquiva Rooster, a tropical bird with brilliant plumage that still lives in the mangroves and forests of Southeast Asia.

Descendants of these birds, the chicken, can be found on farms – and dinner dishes – all over the world.

In his lab at Linking University in Sweden, professor of ethology, Per Jensen, is trying to recreate this domestication process in record time.

When crossing roosters that show less fear than humans, in just 11 generations he noticed a noticeable difference.

His experiments also revealed how close proximity to humans can have a significant impact on animal behaviour.

“If you go into a wild grouse chicken coop, they try to escape and go to the back of the coop, flapping their wings in desperation,” Jensen says.

“The domestic birds we raise come up to you and peck your shoes – they want to interact with humans.”

Banquiva Roosters have changed in other ways, too.

They are more social with their mates and tend to be more interested in exploring their surroundings. They are also larger, females lay larger eggs and have smaller brains than their wild cousins ​​- differences that are also seen in chickens.

Humans have a long history of domesticating animals, a process that stretches back thousands of years.

Charles Darwin was the first to notice that domestic animals such as cats, dogs, and rabbits share certain characteristics in addition to being “meek”.

Pets tend to have more floppy ears and coiled tails than their wild ancestors.

They also have smaller jaws and teeth, and white spots on their fur, and breed often.

This phenomenon is known as the “domestication syndrome”.

The most famous example of domestication syndrome dates back to the 1959 experiment, where Soviet biologists Dmitriy Belyaev and Lyudmila Trout took a few dozen wild silver foxes from a fur farm in Siberia and began selectively breeding the horrific animals.

Incredibly, in just a few generations scientists have bred docile and friendly foxes.

Not only did their behavior change. The foxes looked different, too. They had a shorter nose, flabby ears, spotted spots, and twisted, wagging tails.

Although the reason for this is unknown, a popular theory is that when humans cross animals for domestication, they may inadvertently select individuals with underdeveloped adrenal glands.

growth and reproduction

The adrenal glands or adrenal glands are responsible for the “fight or flight” response, so animals with smaller adrenal glands are less afraid.

The embryonic stem cells that will form the adrenal glands also develop into pigment cells and parts of the skull, jaw, teeth and ears.

Therefore, domestication syndrome may actually be an occasional side effect of pet crossing.

In the case of Jenson Banchival Roosters, one of the biggest differences between wild and domesticated birds is the size of the brainstem, an ancient part of the brain involved in stress reactions.

“The brain is a very expensive organ, consuming 25% to 30% of a mammal’s energy,” says Jenson.

“If you choose animals that grow faster and have a higher reproductive rate, you are placing demands on the way those animals use energy. Chickens don’t have to deal with many of the complex problems that wild animals do, so they can use that energy to grow and reproduction.”

Domestication syndrome may also not be limited to animals that have been intentionally raised by humans.

The mouse probably first entered its storage 15,000 years ago, according to a study by Leor Weisbrod, a zoological archaeologist at the University of Haifa in Israel.

Weisbrod discovered rodent teeth in settlements left over from the hunter-gatherer culture of the eastern Mediterranean around this time.

Since then, the mouse has traveled all over the world, making its home wherever humans live.

There is evidence that living with humans for a long time has altered the DNA of mice.

Researcher Anja Guenther, of the Max Planck Institute in Germany, collected 150 samples from three different subspecies of mice.

Each subspecies began to coexist with humans at different times in our evolutionary history.

NS Muscular home Quran Living with humans began between 12,000 and 15,000 years ago M. Muscle He lived with us for 8000 years, and M. Musculus castaneus A relationship with us began only recently – about 3000-5000 years ago.

Guenther has bred mice for several generations in the laboratory. I took the descendants of the original rodents and tried them using seven different food puzzles.

Inside each puzzle was a food worm, which the mouse could only capture by pushing or pulling the lid, extracting a paper ball from a tube, or opening the window of the LEGO house.

Incredibly, the mice whose ancestors lived the longest with humans were the best at solving food puzzles.

“Evolution must have been on the scene because the animals we use have been kept in standard lab conditions for generations,” says Guenther.

“The mice we tested never lived with humans, but their ancestors did. Living near humans changed the genetic makeup of mice.”

Guenther believes that mice evolved to be better at solving problems because humans hid their food from them.

The battle of minds has made these mice more cunning over time.

“Like an arms race. When we started hiding our food from them, they had to be more creative to find it.”

While living near humans has made some animals (such as mice) more intelligent, it may have the opposite effect on Drosophila, Drosophila black belly.

a D. melanogaster She probably first lived with humans at least 12,000 years ago, when she was attracted by the scent of fruit, she flew into the caves of the ancient peoples living in southern Africa.

Then we followed the flies and our waste around the world.

More than a century ago, these insects were selected as genetic models to analyze their short lives and ease of reproduction.

Since then, l D. melanogaster It has become an indispensable laboratory model, and is used to treat a wide range of biological issues.

Among the geneticists who work with fruit flies, laboratory strains are known to be much less active than their wild ones.

Catching a wild, laboratory-bred fly requires relatively little skill compared to catching a fly flying around a cup of Cabernet Sauvignon.

“Anyone who has ever worked with lab flies knows that if someone slips out of the vial, they are very easy to catch, you just tap the head and they fall,” says Rob Colathenall, an evolutionary geneticist at Temple University in Philadelphia, USA.

To see if anything else was going on, Colathinal compared the genomes of wild Drosophila and lab flies.

Not only did he confirm that the lab strains are significantly less active and interact with other flies than their wild cousins, but he also found evidence that flies living in the lab have undergone rapid evolutionary changes over the past 50 to 100 years.

Rather than finding changes in just one or two genes, Kolathinal found changes in a whole group of genes, particularly those involved in the formation of new neurons in the brain.

These changes may somehow contribute to explaining the different behavior of lab flies.

We don’t know why this happens, but Kulathinal has an interesting theory.

“In research labs, you have to move the flies to a different container every two weeks. When you flip, the quick flies run away from them, and the donkeys stay. So, over generations, you end up choosing slower, capped flies, rather than the faster ones that manage to escape.” .

So what unites the dog, the chicken, the fox, the mouse, and the fly?

Whether they choose to or not, each of them has become closely related to us.

By sharing our lives and researching our remains, each of these species had to overcome their own fear of humans to survive.

“When you start to think about the early stages of domestication going back thousands of years, the absolute first step should be to reduce the fear of humans, because fearful animals can’t thrive and reproduce,” Bear Jenson explains.

What our hunter-gatherer ancestors did not know is that a number of other changes will ride free on the journey of “domestication”.

Read the towards the origin From this article (in English) on the site BBC Future.

You have seen our new videos on Youtube? Subscribe to our channel!