It is known that human and chimpanzee genomes are 99% identical, but our nervous systems develop completely differently and suffer from different problems in old age. These differences make it difficult for scientists to use primates to study some human diseases and discover how Homo sapiens acquired the ability to speak and think clearly.
In recent years, researchers have discovered several hundred new genes that are responsible for brain development and differ in location in the genomes of humans and chimpanzees. However, they were never able to find those sections of DNA that were responsible for the unusually large size of the human brain compared to the rest of the body, and this is one of the main features that distinguishes Homo sapiens from.
And now geneticists from the University of California, Santa Cruz, have found in human DNA a unique gene NOTCH2NL, which is responsible for the unusually large size of our brain and the unique structure of the cerebral cortex. His description was published in the magazine Cell.
“The two main characteristics of humans are a large brain and slow development of the nervous system inside the womb. Now we have been able to uncover the molecular mechanisms of development of both features of Homo sapiens, which, as it turns out, are included in the very early stages of brain development,” says study leader David Haussler.
Scientists were able to find NOTCH2NL by studying the structure of various genes on the first human chromosome, the deletion of which very often leads to the development of microcephaly, and duplication or damage leads to macrocephaly or severe forms of autism.
This section of the genetic code contains a set of genes from the NOTCH2 family, which are responsible for the development of neuronal cells and the formation of future brain tissue in the mammalian embryo. Their structure is almost the same in the DNA of all primates, and they, as scientists from Russia recently proved, work in the same way during the development of the embryo.
While observing the activity of these DNA sections in stem cells, Haussler and his colleagues noticed one simple thing that for some reason all other scientific teams missed. It turned out that an “extra” gene works in human cells, which is absent or does not work in the blanks of neurons of chimpanzees, gorillas and other primates.
Experiments on stem cells have shown that removal of NOTCH2NL leads to the fact that nerve cell blanks begin to mature faster and divide less frequently.
“One stem cell involved in brain growth can give rise to two neurons or another stem cell and one nerve cell. NOTCH2NL forces them to choose the second option, which allowed our brains to grow in size. As often happens in the history of evolution, a small change in the functioning of stem cells led to very large consequences,” the experts conclude.
Having studied the structure of the gene, experts came to the conclusion that it appeared in the DNA of our ancestors approximately 3-4 million years ago as a result of a series of successful errors when copying the first chromosome.
The first error resulted in one of the NOTCH2 family genes being partially copied and inserted into the DNA of the first Homo sapiens. This turned it into a “junk” pseudogene that did not play any role in the functioning of the body. The second error repaired its damaged parts, as a result of which a new section of DNA appeared in the protohuman genome, radically changing the development program of the nervous system. And in the course of subsequent evolution, it was copied several more times.
The Myth of the 1%
Human and chimpanzee DNA are very different
Don Baten
Why do people continue to believe in the myth that there is a 1% difference in DNA between humans and chimpanzees, when in reality the difference is up to 30%?
We still often hear statements that human and chimpanzee DNA are almost identical, and that the difference is only 1%. For example, a 2012 report on DNA sequencing of the pygmy chimpanzee stated:
“Since researchers deciphered the genetic sequence of chimpanzees in 2005, it has been determined that 99% of the DNA of humans and apes is the same. This means that chimpanzees are our closest relatives.”1
This statement was not published by some dubious source. And in the most prestigious scientific journal Science, published by the American Association for the Advancement of Science. Science is considered one of the two most authoritative scientific journals in the world (the second is the British journal Nature).
The first claim of a 1% difference was made in 1975.2 This was long before scientists were able to compare individual “characters” (base pairs) of human and chimpanzee DNA—the first draft of human DNA was published only in 2001, and chimpanzee DNA in 2005. So where did the 1% stated in 1975 come from? The fact is that geneticists have made rough comparisons of very limited sections of human and chimpanzee DNA that were pre-selected to test their similarities. Strands of human and monkey DNA were tested to see how capable they were of connecting to each other, a technique known as DNA hybridization.
Does a 1% difference mean we are “almost identical”?
The human genome contains about 3000 million “characters”. If the 1% figure is correct, the difference would be 30 million characters - the equivalent of 10 Bible-sized books printed. This is 50 times more DNA than the simplest bacterium.3 This is actually a very large difference, exceeding the capabilities of even the most optimistic evolutionary scenario, even over millions of years.4
What's the real difference?
The publication of human and chimpanzee DNA sequencing provided an opportunity to make comparisons. However, even this is not easy to do, because the chimpanzee genome was not built out of the blue. What did the geneticists do? They sequenced small pieces of chimpanzee DNA. Those. Using chemical laboratory procedures, they determined the sequence of chemical symbols. These little strings of “characters” were then connected to the human genome where they thought they would match (computers were used to compare and place the segments). After this, the human genome was removed and a chimpanzee pseudogene was obtained, which supposedly indicated a common relationship with humans (i.e. evolution).
Thus, it was obtained mixed sequence, which is not real. Assuming evolution produced the chimpanzee genome in this way would make the human genome appear larger than it actually is. But even if we take this evolutionary bias into account, the real differences much more than 1%.
In 2007 in Science An article was published about the similarities between human and chimpanzee DNA. The headline was: “Relative Differences: The Myth of the 1%.”2 The author of the article, John Cohen, questions the 1% figure. He refers to data comparisons that were made in the chimpanzee DNA sequencing project. According to the analysis, this difference is at least 5%. Despite this, claims about the 1% continue to appear in the magazine.
To show how wrong this is, Jeffrey Tomkins and Jerry Bergman in 2012 reviewed published studies comparing human and chimpanzee DNA.5 They concluded: “If you take all DNA, and not just pre-selected sections, we can safely conclude that the similarity of the human and chimpanzee genomes is approximately 87%, in any case, no more than 81%.”
In other words, the differences between apes and humans are enormous, perhaps even more than 19%. Dr. Tomkins made his own comparisons and came up with a figure of 30%!6 Moreover, contrary to the expectations of evolutionists, chimpanzees and humans have very different Y chromosomes, which are carried only by men.7
The huge difference between humans and apes does not live up to evolutionary expectations, but rather confirms the fact that we were created separately from animals.
Comparing two complex genomes is no easy task! It is necessary to determine how important different parts of DNA are and what significance different types of differences have. For example, what about human genes that chimpanzees lack, and vice versa? Evolutionary geneticists seem to ignore them and only compare similar genes.
Many comparisons have used only genes that code for proteins (only 1.2% of DNA, and many protein-coding genes in both humans and chimpanzees are almost the same8). Moreover, it was believed that the rest of the DNA was unimportant or “junk.” However, such an opinion is not justified. Almost all DNA has function, again contrary to evolutionary expectations.9 But even if junk DNA were nonfunctional, the differences would be much greater than in protein-coding regions and should be taken into account when determining differences. Humans and monkeys are not 99% identical. No!
Whatever the percentage of similarity, what does it prove?
Neither evolutionists nor creationists made predictions about the percentage of similarity before it was calculated. In other words, whether the percentage of similarity is 99%, 95%, 70%, or whatever, evolutionists will still argue for common ancestry with apes, and creationists will still see it as common design. As we consider the implications of these data, we must understand that we are not dealing with an exact science that can be proven through experiment. Everyone gets their meaning based on their personal worldview.
However, the greater the differences between humans and apes, the more difficult it is for evolutionists to explain them on an evolutionary time scale. That's why they try their best to reduce these differences.
The myth lives on
Comparisons of whole genomes have confirmed that the difference between humans and apes is much greater than 1%. So why does the myth of the 1% persist?
Why magazine Science perpetuated this myth in 2012? In 2007, Cohen cited a statement by geneticist Svante Pääbo, a chimpanzee specialist and member of the consortium of the Institute of Evolutionary Anthropology. Max Planck (Germany): “In the end, the question of the difference between man and ape is more a political, social and cultural question.”2
Perhaps evolutionists will not abandon the myth of the 1% precisely because it makes political, social and cultural sense. They do this for one purpose - to deny the clear conclusions of DNA comparisons that we humans very different from chimpanzees. The myth of similarity is also used to support the view that humans have no special place in this world, and that apes can and should have the same rights as humans.10
The huge difference between humans and apes does not live up to evolutionary expectations, but rather confirms the fact that we were created separately from animals. God created the first man from the dust of the ground (Genesis 2:7) and the first woman from the rib of a man (Genesis 2:22), not from an ape-like creature. Humans, unlike animals, were created in the image of God (Genesis 1:26, 27). They are a special creation. This image was not lost during the Fall, it was damaged,11 so God created people with a special plan, both now and in eternity.
- Gibbons A., Pygmy chimpanzees become, like common chimpanzees, the closest relatives of humans // Science Now, 13 June 2012; news.sciencemag.org.
For two of the world's most authoritative scientific journals - the British Nature and the American Science - to simultaneously devote a significant portion of their next issues to the same topic is extremely rare. And if it happens, it indicates the extreme importance of this topic. So the publication of 12 articles at once devoted to decoding the chimpanzee genome and its comparison with the human genome is, of course, an extraordinary event.
An international consortium was created to implement a project to map and comparatively analyze the chimpanzee genome. It included 67 scientists from 23 scientific institutions in 5 countries - the USA, Israel, Spain, Italy and Germany. The work was coordinated by geneticists from Harvard University and the Massachusetts Institute of Technology in Boston. And blood for DNA analysis was provided by a young male chimpanzee named Clint, an inhabitant of one of the enclosures at the Yerkes National Primate Research Center in Atlanta, Georgia. Unfortunately, in January of this year the donor died of acute heart failure in the prime of his life, at the age of 24. His skeleton is now on display at the Field Museum in Chicago. However, the most important value that humanity inherited from Clint is a portion of his blood, which served as the source material for deciphering and analyzing the chimpanzee genome. Now primates have joined the list of organisms whose genetic material has been fully mapped. This list today already includes hundreds of items: there are molds, bacteria, including causative agents of dangerous infectious diseases (anthrax, tularemia, plague, typhoid), and plants (rice, coffee tree), and insects (malarial mosquito), and birds (eg chicken) and mammals (mouse, rat, dog, pig, cow). However, anthropoid apes occupy, of course, a very special place in this list. According to Robert Waterston, director of genomic research at the University of Washington Graduate School of Medicine in Seattle, "studying chimpanzees, as the closest living relative to humans on Earth, can give us the most information about ourselves." However, before moving on to discussing the results obtained by scientists, I will allow myself a small digression - or, if you like, a reminder - to make it clearer what we are actually talking about.
As you know, any living organism consists of cells, and in the nucleus of each cell there is the same set of genetic information characteristic of a given biological species. This set is called the genome. Chromosomes are the carrier of genetic information. A chromosome is a deoxyribonucleic acid molecule (DNA for short) and consists of two long polynucleotide chains twisted around one another and connected to each other by so-called hydrogen bonds. This molecule is called a double helix, and can be somewhat simplifiedly imagined as a twisted rope ladder. Different species of animals have different numbers of chromosomes. Thus, the human genome consists of 23 pairs of chromosomes - in each pair, one chromosome comes from the father, the other from the mother. The fruit fly - Drosophila - contains 4 pairs of chromosomes in its cell nuclei, while, for example, bacteria have only one unpaired chromosome. Genes are located on chromosomes in strictly defined areas - a kind of unit of heredity. Chemically, genes consist of molecules of 4 nitrogenous compounds - adenine, cytosine, guanine and thymine. These so-called nucleotide bases are repeated in a strictly defined order, forming adenine-thymine and guanine-cytosine pairs. A single gene can contain from several thousand to more than two million nucleotide bases. It is their sequence that determines the specific functions of each specific gene.
Figuratively, the genome can be imagined as follows: the cell nucleus is a library in which instructions for ensuring life are stored; chromosomes play the role of bookshelves; there are books on the shelves - DNA molecules; genes are chapters inside books, and nucleotide bases - adenine, thymine, guanine and cytosine, which are usually denoted by the initial letters of their names A, T, G and C - this is the very alphabet with which the text of the genome is written. The human genome, for example, is a chain of 3 billion 200 million letters.
But the fact that genes exist and that they work is not enough: they must work in different ways, providing certain specific functions. After all, the cells of different organs and tissues - say, skin, liver, heart and brain - are strikingly different from each other. Meanwhile, the core of each of them contains the same set of genes. It's all about gene activity: some genes work in some cells, and others work in others. So chromosomes are carriers not only of genes, but also of those protein factors that control their functions. This set of genes, together with regulatory elements, constitutes the structure inside the cell that provides all the necessary functions.
And now, armed with this knowledge, let's return to the results that were obtained during the deciphering of the chimpanzee genome. For obvious reasons, the greatest interest among both specialists and the general public is the catalog of those differences in the genetic codes of chimpanzees and humans that have accumulated over the past 6 million years, since the evolutionary paths of two species that had a common ancestor. separated. Svante Pääbo, a researcher at the Max Planck Institute for Evolutionary Anthropology in Leipzig and one of the project participants, evaluates the resulting database as follows:
It is an extremely useful tool that will help us find an answer to the question of what genetic mutations explain the striking difference between humans as a biological species and all other animal species. One of the directions of this search comes down to trying to identify the relationship between genetic differences and the activity of certain genes.
First of all, it should be noted that the data obtained surprised specialists. The main surprise is that the chimpanzee genome turned out to be 98.8 percent identical to the human genome. Roughly speaking, the genetic similarity between humans and chimpanzees is 10 times greater than between mice and rats. Amateurs will most likely be struck by such a great similarity, this almost complete identity of genomes, but scientists were surprised by just the opposite: the fact that the difference turned out to be quite significant. Moreover, this figure - a 98.8 percent coincidence - does not fully reflect the state of affairs. It is obtained by comparing individual letters of the genetic code in the coding DNA. Here, scientists counted 35 million discrepancies, which amounted to 1.2 percent of the entire chimpanzee genome, which has about 3 billion 100 million nucleotide pairs. But that’s not all: significant differences were also discovered in the distribution of those sequences of nucleotide bases that form non-coding, “selfish” DNA. These mismatches accounted for another 2.7 percent of the entire genome, for a total of almost 4 percent.
In total, chimpanzees lacked 53 genes that humans have. In particular, the chimpanzee genome is missing three genes that play a key role in the development of inflammation, which is known to cause many human diseases. On the other hand, humans seem to have lost in the process of evolution a gene that protects animals from Alzheimer's disease.
The most significant differences concern genes that regulate the immune system. According to Professor Evan Eichler, a fellow at the University of Washington Graduate School of Medicine in Seattle, this indicates that chimpanzees and humans had to confront different pathogens and fight different diseases during their evolutionary development. Svante Pääbo explains:
First of all, we asked ourselves which DNA segments could provide insight into the origins of certain diseases. We know that some of the genetic structures that cause a particular disease are found in both chimpanzees and humans. Apparently, these structures were inherited by both species from their common ancestor. However, there are diseases for which a genetic predisposition arose during the process of evolution only in humans. In these cases, comparative DNA analysis will give us valuable information about the genetic nature of such diseases and the susceptibility of humans as a species to them.
Analyzing the collected data, the scientists made a kind of computer overlay of the chimpanzee genome map onto the human genome map, which allowed them to identify three categories of so-called DNA duplications - those that are present in the human genome, but absent in the chimpanzee genome, those that are present in the genome chimpanzees, but are absent from the human genome, and those present in the genomes of both species. DNA duplication is a form of mutation in which a section of a chromosome is doubled. In this case, DNA segments with a length of at least 20 thousand nucleotide pairs were taken into account. It turned out that about a third of DNA duplications found in humans are absent in chimpanzees. According to Eikler, this figure surprised geneticists because it indicates a very high frequency of mutations in a short period of time, by evolutionary standards. At the same time, an analysis of DNA duplications unique to the chimpanzee genome showed that although the number of places where they occur is relatively small, the number of copies of duplicated segments is much higher than in humans. And in cases where DNA duplication occurs in both chimpanzees and humans, in chimpanzees it is usually represented by a large number of copies. In particular, scientists discovered a segment that occurs 4 times in the human genome and 400 times in the chimpanzee genome. It is interesting that this region is located near the region that in chimpanzees and other great apes is divided into 2 chromosomes, and in humans is fused into one - chromosome No. 2.
However, the striking differences between monkeys and humans are explained not so much by differences in the genetic code, but by different gene activities, emphasizes Svante Päbo. A group of researchers led by him studied and compared the activity of 21 thousand genes in the cells of the heart, liver, kidneys, testicles and brain of both primates. It turned out that there is no complete coincidence of gene activity in any of these organs, but the differences are distributed extremely unevenly. Surprisingly, scientists recorded the smallest differences in brain cells - they amounted to only a few percent. And the greatest differences were found in the testicles: here every third gene has a different activity. However, this is quite understandable if we keep in mind that chimpanzees do not form monogamous families, but live in groups, a kind of communes, numbering 25-30 individuals of both sexes. That is, “promiscuity” among chimpanzees is much more widespread than among humans. To increase their chances of procreation in promiscuous conditions, male chimpanzees must produce huge quantities of sperm. It is no coincidence that their testicles are ten times larger than those of homo sapiens men. But it’s not just about size, of course, says Svante Päbo:
Our data indicate very high activity of those genes on the Y chromosome that are directly responsible for sperm production.
And for the fact that humans are physically much weaker than chimpanzees, scientists have found a genetic explanation: in monkeys, muscles work 5-7 times more efficiently because in all representatives of the human race, the MYH16 gene, which encodes “myosin” - a muscle fiber protein - is represented by a mutated copy.
However, if we concentrate on the question of what is the main genetic difference between humans as a biological species and monkeys and what explains such a successful expansion of humans during evolution, then the answer, apparently, should be sought in the 6 regions of the genome identified by scientists. In the human genome, these regions, containing a total of several hundred genes, are so stable that they are practically identical in all people; in the chimpanzee genome, on the contrary, they often contain mutations. Apparently, scientists believe, these areas played an extremely important role in the process of our evolution. It is noteworthy that the FOXP2 gene is located in one of these areas, one of the 4 genes responsible for speech development. As experiments have shown, in laboratory conditions monkeys are able to learn a fairly significant set of signs and symbols; chimpanzees living in the wild use a very rich range of sounds for communication; however, they are physically unable to make the movements with their lips and tongue that are necessary for articulate speech. Perhaps it was the mutation of the FOXP2 gene that became one of the key factors that determined such different evolutionary fates of different species of primates.
Ecology
Chimpanzees are known to be our closest living relatives, but few realized this until Charles Darwin popularized the idea in 1859 with his famous On the Origin of Species. Many of us still don’t know what we really have in common and how we differ. Perhaps by learning more about our immediate family, we can learn more about ourselves?
1) Number of types
Chimpanzees belong to the family hominid, to which we ourselves belong. In addition, this family also includes orangutans and gorillas. Currently there is only one species of human: homo sapiens(reasonable person). Many scientists argue over which of our distant ancestors also belonged to humans, but many of them convince everyone that they themselves belong to some “higher” species. Humans are capable of producing fertile offspring, which means we belong to the same species. Chimpanzees actually have two species - the common chimpanzee ( Pan troglodytes) and pygmy chimpanzee ( Pan paniscus) or bonobos. The two species are distinct from each other and do not interbreed. Humans and both of these chimpanzee species descended from the same common ancestor, possibly Sahelanthropa, between 5 and 7 million years ago.
2) DNA
You may have heard that chimpanzees and humans share 99 percent of their DNA. Genetic comparisons are very difficult to make because genes repeat and mutate, so it would be better to say that we share 85 to 95 percent of our genes. Even such numbers seem impressive, although most DNA is used as the basis for cellular functions in almost all living organisms on the planet. For example, human DNA is half the same as a banana, but we can hardly say that we are similar to a banana. 95 percent of matches is also not that much. Chimpanzees have 48 chromosomes - 2 more than us. It is believed that this happened due to the fact that in the human ancestor two pairs of chromosomes were combined into one pair. Interestingly, humans have the least genetic variation of all animals, which is why inbreeding can cause many problems. Two completely unrelated humans will not have as much genetic variation as two chimpanzees born from the same parents.
3) Brain size
The brain volume of a chimpanzee is on average 370 ml, while in humans it is 1350 ml. However, brain size alone does not indicate intelligence. Some Nobel Prize winners had brain volumes ranging from 900 ml to 2000 ml. The structure and organization of different parts of the brain better determine the level of intelligence. The human brain has a higher surface area and is more convoluted than the chimpanzee brain. The comparatively larger frontal lobes allow us to reason logically and think more abstractly.
4) Sociality
5) Language and facial expressions
Chimpanzees have a complex system of greetings and communication, which depends on the social status of the individual. They can communicate verbally, that is, use different sounds - screams, grunts, snorts, screams, puffing and so on. Many of these sounds are accompanied by gestures and facial expressions. Facial expressions - surprise, grin, pleading, consolation - are the same as those of us humans. However, people smile, exposing their teeth, when, as for chimpanzees and other animals, showing teeth is a sign of aggression or danger. For communication, a person mostly uses vocalization, that is, speech. Humans have unique vocal cords that allow us to make a wide variety of different sounds, but we cannot drink and breathe at the same time, like chimpanzees.
Humans have a rather muscular tongue and lips, which allows us to perform masterful manipulations with sounds. That is why we have a pointed chin, whereas like a chimpanzee it is slightly cut off. Chimpanzees do not have as many facial muscles as humans.
6) Food
Humans and chimpanzees are omnivorous creatures, so we eat both plants and meat. However, humans are more carnivorous than chimpanzees, and our digestive systems are designed to digest enough meat. Chimpanzees sometimes kill and eat other animals, often monkeys of other species, but much more often prefer fruit and sometimes eat insects. People are much more dependent on meat because the vitamin B12 we need can only be obtained from meat products.
Based on studies of the digestive systems and lifestyles of some ancient tribes, scientists believe that people adapted to eat meat at least once every few days. Humans prefer to eat at specific times and do not spend the entire day eating, another characteristic of carnivores. This is due to the nutritional properties of the product, as well as the fact that to obtain it you need to go hunting.
7) Sex
Bonobos are famous for their sexual appetites. Common chimpanzees can become angry and use force in some situations when, like bonobos, they prefer to resolve everything peacefully through sexual pleasure. They also greet each other and express affection through sexual stimulation. Common chimpanzees do not have sex for fun, and mating lasts no more than 10-15 seconds, while they can eat or do something else.
Friendship or emotional attachment does not matter in the choice of mating partners, and a female in estrus usually mates with several partners who patiently wait their turn.
Humans are known to experience sexual pleasure, as do bonobos, and procreative sex can last for quite a long time with great effort. Moreover, people often have long-term relationships with partners. Unlike humans, chimpanzees have no concept of sexual jealousy or competition, since they are not prone to long-term relationships with the same sexual partner.
8) Body structure
Both humans and chimpanzees can walk on two legs. Chimpanzees stand up only when they need to look into the distance, but usually walk on all fours. Humans walk at an early age and have a bowl-shaped pelvis that supports all internal organs. Chimpanzees do not need to support internal organs since they do not usually walk on their hind legs. Childbirth in chimpanzees is much easier than in humans, since our pelvis is perpendicular to the birth canal. The toes on the human foot are all located on one side, which allows one to push off while walking, when, like a chimpanzee, the big toe on the foot is separate, just like on the hand, which makes the feet look like hands. A chimpanzee uses all its limbs to climb trees or move on the ground.
9) Eyes
Humans have white eyeballs that are visible around the pupils, while chimpanzees have dark brown ones. By looking at a person, you can understand where he is looking, and there are several theories about why this is necessary. This may be an adaptation to more complex social situations where it is important for us to understand the direction of another person's gaze. It can also help a person when hunting in groups, where eye direction is a vital ability for communication. Or it is just a mutation with no particular purpose - white eyeballs can also be seen in some chimpanzees.
Both humans and chimpanzees can distinguish colors, which allows us to select ripe fruits and plants to eat, and we also have binocular vision - that is, our eyes look in the same direction. This allows you to see the depth of objects, which is very important for hunting. It would be very inconvenient if our eyes were located on both sides of our heads, like many animals that do not need to hunt, such as rabbits.
10) Use of tools
For many years it was believed that only humans know how to use tools. However, observations of chimpanzees in the 1960s showed that this was not the case - the monkeys could use the pointed branches to catch termites. Both humans and chimpanzees are capable of changing the environment in order to obtain objects - tools - that help solve pressing problems.
Chimpanzees can make darts, use stones as hammers and anvils, and roll leaves to make homemade washcloths. It is believed that when a person began to walk upright, he needed to use tools more, and it was we who began to turn these tools into objects of art. Today we are surrounded by objects that we created out of necessity.
Another genetic experiment by Chinese researchers has caused controversy in the scientific community. Specialists from several research centers in China, in collaboration with colleagues from the United States, introduced the human version of the gene responsible for brain growth into the genome of monkeys.
It is noted that after modification, macaque embryos developed naturally. As a result, 11 GM monkeys were born in the laboratory, but only five survived. Each of these individuals had between two and nine copies of the human MCPH1 gene.
According to the researchers, none of these animals had brain sizes that were larger than normal, although the development of this organ took longer than usual.
MRI scans of the brain and analysis of tissue sections showed a change in the nature of neuronal differentiation and a delay in the maturation of the nervous system, which is characteristic of people, writes the China Daily news agency.
To be clear, one of the key differences between humans and non-human primates is that we take much longer to form neural networks during development, making childhood much longer. Apparently, the same trait appeared in this case in macaques.