Why are cats’ brains getting smaller and smaller?

Humans first domesticated cats about 10,000 years ago.
In the following days, this furry animal gained thousands of favors due to its cute appearance and unique personality, attracting countless people to take care of it and feed it.
However, a study published in “Royal Society Open Science” in January this year showed that humans’ love for cats is causing cats’ brains to seriously “shrink”…

Brain size “shrinks”

How are cats from 10,000 years ago different from today? From the outside, there is little difference between the two.
The difference is more reflected in the “internal”. After comparing the skull size and brain size of modern domestic cats and their ancestors, African wildcats and European wildcats, researchers found that compared to their wild ancestors, cats who live in harmony with humans in modern society have “brain capacity” (here refers to the skull) size and brain size) are much smaller – about 25% smaller.
After reviewing the data, the researchers determined that this kind of brain size change is quite common in animals. Earlier research data showed that similar conditions exist in dogs (shrunk by 29%), sheep (shrunk by 24%), pigs (shrunk by 34%), and cattle (shrunk by 26%).
In a special analysis of cattle, scientists pointed out: “The more interactions with humans and the closer the relationship, the smaller the brain of the cow.” For example, cows have relatively smaller brains because they need to carry out a series of production cooperation with humans. ; The black bulls used in bullrings have been alienated from humans since they were young because they need to cultivate hostile emotions, and their brains are relatively large.

Cats have not become stupid

One thing to clarify here: Just because the brains are getting smaller does not mean that today’s cats are dumber than cats of the past.
“Brain size does not represent the level of intelligence. To evaluate the intelligence of animals, you may be able to count the number of neurons in their cerebral cortex. The number of neurons not only reflects the richness of the animal’s mental state, but also reflects their predictions about the future based on experience. The ability to predict.”
For example, the brain size of a bear is about 10 times that of a cat, but the number of neurons in the two is almost equal, and their intelligence may be almost the same; the brain size of a raccoon is about the same as that of a cat, but their neurons are More, so in theory, raccoons may be more resourceful than cat owners.
In comparison, dogs have larger brains and more neurons than cats. As for the question “Who is smarter, cats or dogs?” that often sparks passionate debate? I believe you all have the answer in your mind.
Brain shrinkage may be ‘domestication syndrome’

Speaking of which, why do cats today have smaller brains?

“Obviously, domestication has had a major impact on the evolution of animals,” the article states.
Some researchers speculate that brain shrinkage is a form of “domestication syndrome.” Domestication may have unintentionally changed the way animals’ brains develop. Under its influence, neural crest cells, a type of cell critical to the development of the nervous system, became less capable of proliferating and decreased in number. Due to the insufficient quantity of basic “building materials”, the volume of the constructed structure cannot be compared with the original volume.
Some people also believe that the overall “shrinking” of the brain is because the limbic system in the brain has become smaller.
The limbic system is a complex area responsible for fear, attention, and aggression. Its “shrinking” means that today’s animals are more adapted to their environment and are not as easily frightened as before.
This speculation is consistent with previous conclusions drawn by scientists from cattle studies. In the past, when they were not domesticated, animals may have regarded humans as strange “predatory beasts” and remained alert at all times to guard against the approach of the latter. With the advancement of domestication, animals’ fear and aggression towards humans have long been reduced. Especially animals like cats that have lived with humans for a long time. In their eyes, humans are just ordinary “shit collectors” who can get close to them without fear.

To sum up, if you have a bad temper and are brave, the probability of growing a “big head” is quite high.

Over the past three million years, the size of the human brain has increased approximately threefold, from the 450-gram brain of Australopithecus ape in the human lineage to about 1,400 grams of modern human brain, becoming the “strongest” known in the biological field. brain”.
In the process of evolution and social progress, humans continue to acquire new skills, including domesticating animals. Ancient humans directly interfered with the natural reproduction process of wild animals through domestication, which may have caused some animals to have rounder faces, shorter muzzles, shorter tails, thicker bodies, and even smaller skulls of some animals. Most of the domestic animals we see today are significantly different from their primitive ancestors. These characteristics that appear after domestication are collectively known as Domestication Syndrome.
In fact, not only now, Darwin discovered this phenomenon as early as 140 years ago. However, he himself could not find out the reason. Until now, this question has remained one of the unanswered questions in genetics.
In a new study published in Royal Society Open Science on January 26, 2022, researchers from the University of Vienna in Austria and the University of Edinburgh in the United Kingdom confirmed that as cats were domesticated over the past 10,000 years, their The size of the skull has been significantly reduced.
This means that the brains of cats and dogs have evolved to be “maximized”; while the brains of cats are getting smaller and smaller. The discovery could yield important new insights into domestication syndrome, or how animals adapt to being raised by humans.
In the study, researchers compared skull size (a measure of brain size) in domestic cats, a common laboratory animal, with wildcats from Europe and Africa, which are now genetically confirmed to be the ancestors of domestic cats. species.
The researchers also looked at hybrids of wild and domestic cats and found that their brain sizes fell between the measurements of the other two groups of cats, with domestic cats indeed having larger skulls than the European wildcat (Felis silvestris) and the domestic cat’s wild ancestor. African wild cats (Felis lybica) are smaller.
The researchers further found that the offspring of crosses between domestic cats and European wildcats had skull volumes that were between those of the two parent species. This finding corroborates past research results.

Scientists have been studying cat brains since the 1960s and 1970s, and the trend toward smaller brains has also been observed in sheep, dogs and rabbits. Clearly, these domesticated animals have undergone significant changes.
Researchers have proposed the idea that natural selection for tameness during domestication causes animals to produce fewer neural crest cells (associated with excitability and fear). This in turn may lead to changes in stress response, brain size, and overall body shape.
The researchers also examined the palates of domestic and feral cats in the area but found no significant changes. There is some thought that a reduction in neural crest cells would lead to shorter nose length and smaller skull size, but this was not reflected in this set of data.
While the study’s conclusions are not entirely new, in some cases they do update data from previous decades and give scientists working on domestication theories more new information to analyze.
Researchers believe comparisons of brains are often based on older, hard-to-access literature, and in some cases, domesticated animals are compared to wild species that are no longer thought to represent the true ancestors of domesticated animals. species.

In domestication research, there is also a view that compared with dogs, cats are not truly domesticated animals, or can only be regarded as a “semi-domesticated” species. The idea is that cats choose to be with humans, not humans choosing cats, and therefore cats cannot be considered fully domesticated.
Researchers believe this view is inaccurate. This is despite the fact that cats’ path to domestication is often viewed as benefiting only cats, not humans. Cats may not be as “useful” to humans as dogs or horses, but their role in protecting grain harvests from rodents was an important driver of domestication, and their association with humans goes beyond simply hunting for food. Just a food source. Researchers say domestic cats continue to be chosen as pets because of their docility, which makes them suitable candidates for domestication.
Ultimately, the researchers say data from more species will need to be collected to fully understand the effects of domestication on cats, including their brain size, but the information gathered so far still has limitations.
The scientists concluded: “We must acknowledge that we are comparing current or recent populations of wild animals to domesticated populations, rather than their true ancestral populations. This is always a puzzling point because we rarely have access to to the ancient ancestors of modern domesticated animals, and fortunately ancient animal DNA can help partially solve this problem.”