In 1975, Mary-Claire King and Allan Wilson published an article in the journal Science on the genetic similarity between chimpanzees and humans. Alas, this article has been cited more often to confirm the "almost complete identity" of chimpanzees and humans, rather than to convey its main point that nobody really understands how macroevolution happened.
In short, King and Wilson compared the amino acid sequences of several chimpanzee and human proteins (such as hemoglobin and myoglobin) and found that the sequences were either identical or nearly identical. What was their conclusion? "... The sequences of chimpanzee and human polypeptides studied to date are, on average, more than 99% identical..»
So, through the fault of lazy readers (who did not read that article to the end), "Myth of 1%" of the genetic difference between Homo sapiens and Pan troglodytes, as Jon Kogen later called it in his Science article in 2007.
There were other experiments that seemed to confirm the similarity by 98.5%. But it was relative figure, since the comparison was made only in the coding parts of DNA and only among similar genes with "single base substitution". "Insert-deletion" and "repeats" in DNA were not taken into account, because then it was not possible to compare them. Subsequent comparative analyzes using new technologies made it possible to refine the data.
In 2002, Roy Britten compared "insert-deletions" and found that they increase the genetic difference by another 4%. Since then, the imaginary "identity" has been less than 95%!
An illustration of the difference in genomes discovered by Matthew Hanna's group.
In 2006, Matthew Hann et al. found that insertion-deletion adds even more difference than Britten had determined—namely 6,4% (i.e. 1418 genes). Total estimated match reduced to 92-93% .
And finally, in 2008, an attempt was made to conduct a comparative analysis of huge sections of "repeats" (the function of which is not yet completely clear), as a result of which it turned out that the absolute similarity between human and chimpanzee DNA can be less than 90%.
It may seem that the difference between 98% and 95% is quite insignificant, but if you consider that human DNA consists of 3 billion base pairs, then a 3% difference would be 90 million base pairs! And besides, as many years of research confirm, the cardinal differences between humans and chimpanzees are influenced not so much by the difference in the genes themselves, but in their expression - that is, their participation in the production of proteins. However, there is not a single reason to downplay the difference in DNA sequences.
Help from Wikipedia:
Protein-coding sequences make up less than 1.5% of the genome. Leaving aside the known regulatory sequences, the human genome contains a host of objects that look like something important, but whose function, if any, is currently not clear. In fact, these objects occupy up to 97% of the entire human genome.
Every now and then, in various sources, the myth that "the pig is genetically closer to humans than the chimpanzee" pops up, and this delusion is very stable.
Partly, due to the fact that the internal organs of a pig are very well suited for transplantation to humans. And Bernard Werber added fuel to the fire with his rot "Father of Our Fathers" (but there, one must understand, pure fantasy).
But what do geneticists think about this, how genetically close are pigs and humans?
Vladimir Alexandrovich Trifonov: The genome homology numbers are of rather low value, it all depends on what we are comparing with: whether we take into account structural changes in the genome, whether we take into account repeated sequences, or whether we are talking only about replacements in coding regions.
As a comparative cytogeneticist, I can say that the evolution of porcine karyotypes was accompanied by a large number of rearrangements - even from a common ancestor with ruminants and cetaceans, 11 breaks and 9 inversions separate porcine karyotypes, plus 7 mergers and three inversions occurred in the pig line after the separation of peccaries. When we build molecular phylogenies based on sequencing data, the pig is never related to humans, there are many such data, and they are much more accurate and reliable than general estimates of molecular differences. There are hundreds of thousands of differences between the pig and human genomes, so special programs are used to evaluate them, which, based on the similarity and difference of many features, build phylogenetic trees. The position on the phylogenetic tree just reflects the degree of similarity or difference between species.
Phylogeneticists have their difficulties and their controversies, but today few people doubt some of the basic ideas. Here, for example, are three modern papers where phylogenies were built by different groups (who are generally recognized experts in this field), based on a variety of characters taken from DNA sequences:
Conrad A. Matthew et al. Indel evolution of mammalian introns and the utility of non-coding nuclear markers in eutherian phylogenetics. Molecular Phylogenetics and Evolution 42 (2007) 827–837.
Olaf R. P. Bininda-Emonds et al. The delayed rise of present-day mammals. Nature, Vol 446|29 March 2007.
William J. Murphy et al. Using genomic data to unravel the root of the placental mammal phylogeny. Genome Res. 2007 17: 413-421.
In all published phylogenies (see the figure below), the pig firmly takes its place among artiodactyls, and man "does not jump out" from the order of primates, i.e. the data obtained from the analysis of different DNA sequences give the same answer to this question, confirming in this question the phylogenies constructed according to morphological characters as early as the 19th century.
The figure shows that the pig is farther from the person than the mouse, rabbit and porcupine. Source: William J. Murphy et al. Using genomic data to unravel the root of the placental mammal phylogeny. Genome Res. 2007 17:418.
Mikhail Sergeevich Gelfand: to be honest, I won’t say right away about the exact % of DNA matches, and it’s not very clear what that would mean: in the genes? in intergenic intervals? most of the genome of a pig with a human simply does not align (unlike chimpanzees), it makes no sense to talk about% matches there. In any case, a pig is further from a person than a mouse. But who is close to pigs is whales (although they are even closer to hippos).
Question. Konstantin Zadorozhny, editor-in-chief of the journal for teachers "Biology" (Ukraine): In the e-book of the respected S. V. Drobyshevsky "The Extracting Link" it is indicated that the second human chromosome was formed as a result of the fusion of two chromosomes of the ancestral species, which remained unfused in chimpanzees (this I personally met the information before, but it was practically not covered in popular publications). Accordingly, the question is for one of the experts. At what stage of human evolution (early hominids, australopithecines, early homos, etc.) did this chromosomal aberration occur? Is it possible to determine this?
Answer. Vladimir Alexandrovich Trifonov: I will be happy to answer your question, since the fusion of the chimpanzee and human ancestral chromosomes (corresponding to the chimpanzee PTR12 and PTR13 chromosomes) is indeed the last significant event that changed the human karyotype.
Let's start with the ancestor of great apes - the data of comparative genomics indicate that these two elements of the karyotype were acrocentric, and it was in this unchanged form that they were preserved in the orangutan.
Further, in the common ancestor of humans, gorillas, and chimpanzees, a pericentric inversion occurs, turning one of these elements into a submetacentric (this element corresponds to the chimpanzee PTR13 chromosome and the gorilla GGO11 chromosome). Then, in the common ancestor of humans and chimpanzees, another pericentric inversion occurs (in the homologue of the PTR12 chromosome of the chimpanzee), turning it into a submetacentric.
And, finally, the last event in the Homo line is the fusion of two submetacentrics with the formation of the human chromosome HSA2. This is not a Robertsonian fusion (centric), but a tandem one, with the PTR12 centromere retaining its function, the PTR13 centromere being inactivated, and ancestral telomeric sites found at the point of tandem fusion (Ijdo et al., 1991).
According to the time of formation of the human HSA2 chromosome, one can only say that the fixation of this rearrangement occurred after the divergence of the human-chimpanzee lines, i.e. not earlier than 6.3 million years ago.
I don't think the great apes have an increased frequency of Robertsonian translocations. They have very conservative karyotypes that change little over millions of years; during this time, dozens of significant transformations took place in the karyotypes of species of other taxa. There is evidence from clinical cytogenetics indicating a frequency of 0.1% in human meiosis (Hamerton et al., 1975). However, genome analysis shows that such rearrangements were not fixed in the human lineage.
Question. Alexey (letter to the Editor): Questions arise in the course of reading lectures on genomics for Phystech. Gene not defined...
Answer. Svetlana Aleksandrovna Borinskaya: It was easy to define a gene when not much was known about it. For example, "a gene is a unit of recombination", or "a gene is a section of DNA encoding a protein", "One gene - one enzyme (or protein)", "One gene - one trait".
Now it is clear that the situation is more complicated with both recombination and coding. Genes have a different structure, sometimes quite complex. One gene can encode many different proteins. One protein can be encoded by different DNA fragments located at a great distance in the genome, the products of which (RNA or polypeptide chains) are combined as they mature into one polypeptide.
In addition, the gene contains regulatory regions. And there are genes that do not code for proteins, but only for RNA molecules (besides the well-known ribosomal RNAs, these are RNA molecules that are part of other molecular machines, recently discovered microRNAs and others).
RNA types). Therefore, there are now many definitions of what a gene is. The gene is a concept that is difficult to fit into one short, all-encompassing definition.
Answer S.B.: The genome is DNA. Or a complete set of DNA molecules of an organism (in a single cell) = genome.
However, we do not mean cells in which DNA rearrangements occur during development (such as cells of the immune system in mammals or animal cells in which "chromatin diminution" occurs - the loss of a significant part of DNA during development).
Answer S. B.: E. coli is the most studied bacterium, but even for it, functions are still not known for all genes. Although the amino acid sequence of the protein can be "derived" from the nucleotide sequence of the gene. For well-studied bacteria, for about half of the genes, the functions of the proteins they encode are known. For some genes, experimental confirmations of functions have been obtained, for some, predictions are made based on the similarity of the protein structure with other proteins with known functions.
Question. Alexei: Do I understand correctly that the number of nucleotides in a gene is different for each gene? There is no pattern here.
Answer S.B.: Quite right.
Question. Alexei: Can different genes have exactly the same nucleotide sequence, but differ only in location?
Answer S.B.: There are probably no absolutely identical genes. But there are genes located in different parts of the genome with a very similar nucleotide sequence. Only they are called not "similar", but "homologous". These genes resulted from the duplication of an ancestral gene. Over time, nucleotide substitutions accumulate in them. And the closer the time of duplication is to us, the more similar the genes are. Gene duplications are found in all organisms, from bacteria to humans.
At the same time, different genes in different people can be contained in different numbers of copies. The number of copies can influence the activity of the corresponding gene products. For example, a different number of genes for certain cytochromes affects the rate of metabolism and excretion of drugs from the body and, accordingly, it is recommended to use different doses.
Question. Alexey: I would also like to hear the opinion of specialists regarding the materials provided by Garyaev (meaning the so-called "wave genome" theory). He claims that his experiments are confirmed experimentally in laboratories. Is it so. What can you say to this?
Answer S.B.: You can also say whatever you like. But the scientific world will pay attention to your claims only if they are published in peer-reviewed scientific journals, and even presented with a description of the details of the experiment, allowing it to be repeated.
Mr. Garyaev does not publish his "discoveries" in scientific journals, he only tells journalists. There is no data on his "experiments", only his words. Let at least the laboratory journal show with a detailed record of the conditions and results of the experiments.
1. Humans have 23 pairs of chromosomes, while chimpanzees have 24. Evolutionary scientists believe that one of the human chromosomes was formed by the fusion of two small chimpanzee chromosomes, rather than an inherent difference resulting from a separate act of creation.
2. At the end of each chromosome is a strand of a repetitive DNA sequence called a telomere. Chimpanzees and other primates have about 23 kb. (1 kb is equal to 1000 nucleic acid heterocyclic base pairs) of repeating elements. Humans are unique among all primates, their telomeres are much shorter: only 10 kb long. (kilobases).
3. While 18 pairs of chromosomes are "virtually identical", chromosomes 4, 9 and 12 indicate that they have been "remade". In other words, the genes and marker genes on these human and chimpanzee chromosomes are not in the same order. It makes more sense to think that this is an inherent difference due to the fact that they were created separately and not "remade" as evolutionists claim.
4. The Y chromosome (sex chromosome) is especially different in size and has many marker genes that do not match (when lined up) between humans and chimpanzees.
5. Scientists have prepared a comparative genetic map of the chimpanzee and human chromosomes, in particular the 21st chromosome. They observed "large, non-random patches of difference between the two genomes." They found a number of sites that "could correspond to insertions that are specific to the human lineage."
6. The size of the chimpanzee genome is 10% larger than the size of the human genome.
These types of differences are usually not taken into account when calculating the percentage similarity of DNA.
In one of the most extensive studies comparing human and chimpanzee DNA, researchers compared more than 19.8 million bases. Although this number seems large, it represents less than 1% of the genome. They calculated an average identity of 98.77% or 1.23% difference. However, in this study, as in others, only substitutions were taken into account and no insertions or deletions were taken into account, as was done in Britten's new study. A nucleotide substitution is a mutation where one base (A, G, C, or T) is replaced by another. Insertions or deletions are found where nucleotides are missing when two sequences are compared.
Replacement Insertion/deletion
Comparison between base substitution and insertion/deletion. Two DNA sequences can be compared. If there is a difference in nucleotides (A instead of G), then it is a substitution. Conversely, if there is no basis, then it is considered to be an insertion/deletion. It is assumed that the nucleotide was inserted into one of the sequences, or it was removed from another sequence. It is often difficult to determine whether a difference is the result of an insertion or a deletion. In fact, inserts can be of any length.
Britten's study looked at 779 kilobases of nucleic acids in order to scrutinize the differences between chimpanzees and humans. Britten found that 1.4% of the bases were changed, which was consistent with previous studies (98.6% similarity). However, he found a much larger number of inserts. Most of them were only 1 to 4 nucleotides long, while there were a few nucleotides that were over 1000 base pairs long. Thus, insertions and deletions added 3.4% additional different base pairs.
Whereas previous studies have focused on base substitution, they miss the biggest contribution to the genetic differences between humans and chimpanzees. The missing human or chimpanzee nucleotides were found to be twice as many as the number of nucleotides replaced. Although the number of substitutions is about ten times greater than the number of insertions, the number of nucleotides involved in insertions and deletions is much greater. These inserts were noted to be present in equal numbers in human and chimpanzee sequences. Therefore, insertions or deletions did not occur only in chimpanzees or only in humans, and they can be interpreted as an inherent difference.
Will evolution be questioned now that the similarity in chimpanzee and human DNA has dropped from >98.5% to ~95%? Probably not. Regardless of whether the degree of similarity drops even below 90%, evolutionists will still believe that humans and apes descended from a common ancestor. Moreover, the use of percentages obscures a very important fact. If 5% of DNA differs, then this corresponds to 150,000,000 base pairs of DNA that are different from each other!
A number of studies have shown significant similarities between nuclear DNA and mitochondrial DNA in modern humans. In fact, the DNA sequences of all humans are so similar that scientists generally conclude that there is "a recent single origin of all modern humans, with a general replacement of older populations." To be fair, evolutionists' calculations of the date of origin of the "most recent common ancestor" (CHOP), i.e., "recent common ancestry," came up with a number of 100,000-200,000 years ago, which by creationist standards is not recent. These calculations were based on comparisons with chimpanzees and the assumption that the common ancestor of chimpanzees and humans appeared approximately 5 million years ago. But studies that used generational comparisons and genealogical comparisons of metachondrial DNA pointed to the origin of even more recent SNOP - 6,500 years!
A single-generation study of observed mutations points to a more recent common human ancestor than phylogenetic calculations suggesting a relationship between humans and chimpanzees. It is hypothesized that mutational regions are the cause of the differences between these classes. However, in both cases they rely on uniformitarian principles, namely that percentages calculated in the present can be used to extrapolate the time of events into the distant past.
The above examples demonstrate that the conclusions of scientific studies can be different depending on how these studies are conducted. Humans and chimpanzees can have 95% or >98.5% DNA similarity depending on which nucleotides are considered and which are excluded. Modern man may have a single recent ancestor who appeared
Links and notes
Exactly 200 years ago, on February 12, 1809, Charles Darwin was born. In many ways, it was through his efforts that people finally understood who they were. A species of higher apes. And the clearer this, for some, unpleasant answer became, the more acute the question arose - how does a person differ from other higher primates.
And it's surprisingly difficult to answer. Although the differences from the closest of the surviving relatives, chimpanzees, are visible to the naked eye, it is not possible to present a criterion - a necessary and sufficient condition - for the belonging of any monkey to humans.
According to individual signs - even anatomical, even craniometric, even phrenological - there are more than enough differences. Which allowed for long and long years to rank peoples and races according to the “degree of perfection”, or evolutionary distance from monkeys. The ranking itself was carried out by the Europeans, because the main measure of perfection was, as a rule, the whiteness of the skin. Signs on which blacks or Asians moved farther from monkeys (for example, the length of the penis or the amount of hair on the body, respectively) were not considered.
But there is no general definition that distinguishes a person from a monkey.
Don't believe? Try it yourself at your leisure to come up with such a criterion, and so that without any reservations. The time to complete this task will be limited only by your stubbornness.
But even if it was not possible to fully understand the differences, this is not a reason to abandon the search for their reasons - albeit formal ones. By the end of the 20th - beginning of the 21st centuries, anthropologists became interested in genetics. And since "the genotype determines the phenotype," let's compare the DNA of humans and chimpanzees, and maybe we'll find some kind of "gene of humanity." Then we will figure out what external and internal differences this gene is translated into.
The genomes of chimpanzees and several other monkeys read in recent years - gorillas, orangutans and macaques - have somewhat disappointed those who hoped to find a person in their comparison with the genome of Craig Venter and. We consist of almost identical proteins, and even the frequency of the main type of mutations - single nucleotide substitutions ("snip") in the genes of these proteins (and this is the basis of variability and interspecies differences in many lines of living beings) in primates - on the way from monkey to man is steadily fell. The activity of mobile genetic elements - transposons and the like, with which significant rearrangements of the genome are sometimes associated even in the absence of changes in the proteins themselves, also fell.
At the same time, purely subjectively, the differences between humans and even the most perfect of other primates seem to be more significant than the differences between, say, a chimpanzee from a gorilla. If only because chimpanzees and gorillas still get along with each other nearby, on the same continent, and man has captured the entire planet. And not out of evil, but simply because its activity is able to change landscapes over vast territories, it threatens the existence of the same gorillas.
A group of American, Spanish and Italian scientists led by Ivan Eichler from the University of the US State of Washington decided to deal with the second type of mutation - gene copy number variations (CNV, copy number variations). With such mutations, unlike "snip", nothing changes in the genetic code of a protein. Instead, as the name implies, there is a change in the number of copies - a gene encoding a protein can be copied twice when rewriting the genome, which means that the protein itself will be synthesized twice as much. The reverse situation is also possible, when the gene is completely deleted.
Eichler and colleagues compared the CNV profiles of macaque, orangutan, chimpanzee and humans. According to modern ideas, it was in this order that the branches of the evolutionary tree grew, at the ends of which the listed species of monkeys now sit. results comparisons are published in the latest issue of Nature, dedicated to the 200th anniversary of the birth.
As it turned out when comparing monkey DNA, the rate of duplication of genes on the branch leading to chimpanzees and humans has doubled.
Between about 8 and 6 million years ago, when the last common ancestor of humans and chimpanzees, who is not also the ancestor of the gorilla, lived, on average, 60 genes doubled per million years. In the common ancestor of all hominids, this rate, according to the analysis, is 3-4 times less. True, the time span of this older branch before branching into pongins (orangutans) and hominins (chimpanzees, gorillas and humans) is longer, so the total number of doublings is practically the same.
According to Ivan Eichler, it is striking that this acceleration of doublings occurred at exactly the same time when the rate of accumulation of single mutations, "snip", on the contrary, fell sharply for all hominids. At the same time, scientists also found examples of the independent occurrence of the same doublings in different monkeys - for example, doublings that an orangutan and a person have, but not a chimpanzee.
Over the approximately 2-3 million years of the existence of a common ancestor of chimpanzees and humans, we have collectively accumulated 20-25 million base pairs that are copies of other segments of the genome. Over the next 5-6 million years - only 16-17 million pairs. At the same time, doublings do not occur evenly throughout the genome, but in separate, for some reason, unstable regions.
Even more surprisingly, the main duplication spurt refers specifically to the common branch of chimpanzees and humans.
However, Eichler and his colleagues, it seems, do not intend to draw not the most pleasant conclusions.
“There is still no definitive answer as to why humans and chimpanzees are so different,” He speaks Thomas Marc-Bone of Eichler's research group. “Maybe the difference of a person is not there at all.”
Some scientists believe that genes are really not so important for a person. As Nature columnist Erica Hayden says in a popular article, published in the same anniversary issue of Nature, a growing number of scientists are inclined to think about the disproportionate role of the "cultural" component - as opposed to the "material", genetic, DNA-based - in the human heritage. Human abilities for technological innovation and education to some extent softened the pressure of natural selection in its "Darwinian" form, allowing us to retain many "harmful" mutations in the genome and not fix many "useful" ones in it.
A modern example of this is the Oxford geneticist Gilin McQueen. Thanks to glasses, even people with not very good eyesight can live to adulthood and pass on their genes - including poor eyesight - to the next generations. Our distant ancestors did not have such chances.
At the same time, no one is going to throw "material" genetics off its pedestal or expose its leading role in the transfer of information from generation to generation. An important role is also played by differences in the number of copies of the gene. It's just that "now it's time to figure out what all these differences mean and how they are reflected in the genes," concludes Marc-Bone.
