Y-chromosome Adam – Naming
Y-chromosome Adam is named after Adam in the Book of Genesis. The name implies that Y-chromosome Adam was the only male of his time, but this is not in fact the case. He is not a man, but rather a title that refers generically to all the ancestors who passed the Y chromosome on to present-day men.
Y-chromosome Adam – Time Frame
According to molecular clock and genetic marker studies, Y-chromosome Adam probably survived between 60,000 and 90,000 years ago. Although Y-chromosome Adam became close to the descendants of granulosa Eve, they were separated by at least 30,000 years, or possibly 1,000 generations. This is found from the difference in reproductive methods of males and females.
The Y-chromosome Adam is more recent than the granulosa Eve, corresponding to a greater difference in the probability distribution of men with offspring in the Paleolithic than of women with offspring at that time. Normally fertile women had a near equal chance of producing a certain number of normally fertile offspring, while normally fertile men were more mixed, with some having no sons, or others having many.
The Kegel exercise, also known as the pelvic exercise, was published in 1948 by Dr. Arnold Kegel in the United States and is performed by repetitively scaling part of the pelvic muscles (now commonly known as the “Kegel muscles”). Tools have been invented to assist with this exercise, but many are ineffective. Kegel exercises are often used to reduce urinary incontinence, postpartum incontinence in women, and to reduce premature ejaculation in men.
Mitochondrial Atlas
X chromosome (left) and Y chromosome (right) Atlas
The Y-chromosome Adam is not the same person in human history, and the Y-chromosome Adam of all present-day humans will be different from the Y-chromosome Adam of past or future humans. When the male branch disappears, a more recent person will become the new Y-chromosome Adam. In times of rapid population growth, the paternal branch is less likely to disappear than when there is a population bottleneck.
Y-chromosome Adam – Explanation
There are tens of thousands of human genes, the vast majority of which are located on chromosomes in the nucleus, but a very small number (37 to be exact) are located in the mitochondria of the cytoplasm. Each cell has thousands of mitochondria, which are the “respiratory organs” of the cell and provide energy for cellular activity.
During spermatogenesis, the majority of mitochondria are removed, leaving only a very small number to provide energy for sperm motility. At fertilization, the sperm nucleus enters the egg and fuses with the egg nucleus, while the remaining mitochondria in the sperm are kept out and do not enter the egg. Thus, the next generation will have half of the nucleus genes from the sperm and half from the egg, but all of the mitochondrial genes from the egg. In other words, mitochondrial genes are inherited maternally. If a mother does not give birth to a daughter, then her mitochondrial genes are lost.
In the process of producing sperm and eggs, the genes in the nucleus are reorganized, disrupting the original arrangement. But the genes of the mitochondria do not recombine, so it is passed on quite faithfully. However, there is no such thing as 100% completely faithful inheritance; during the transmission of mitochondrial genes, just like genes in the nucleus, rare genetic mutations still occur that alter the gene sequence.
As more mutations accumulate in mitochondrial genes over time, the greater the differences in mitochondrial gene sequences between offspring individuals. In general, the greater the difference in mitochondrial gene sequences between two individuals, the longer they have been separated from their common ancestor and the more distantly related they are, and vice versa.
In this way, by comparing the differences in mitochondrial gene sequences between individuals now, we can compare how related they are, and then, based on the mutation rate of the genes, we can figure out when the common ancestor of these individuals lived. The further forward in time, the more mutations there are, but if we go back further, the fewer mutations there are, and eventually we must reach a point where there are not all the existing mutations, but only one prototype.
At this point we say that we have found the common ancestor of the mitochondria of all people now. By tracing the genealogy of mitochondrial genes, a crossover point was found about 140,000 years ago, suggesting that the mitochondrial genes of all existing people were passed on to a single woman 140,000 years ago. She has been called “Mitochondrial Eve”.
The Y chromosome in the nucleus, which determines male sex, is also inherited unisex, except that it is inherited paternally, from father to son. By comparing the differences in Y chromosome sequences between individuals, we can also calculate that the Y chromosome present in all individuals came from a single male about 60,000 years ago. He is called “Y-chromosome Adam”.
The terms “Eve” and “Adam” were originally used metaphorically, but the general public misunderstood the discovery and thought it meant that there was only one woman or one man at the time. Fundamentalist Christians have even taken this discovery as proof that the story of Adam and Eve in the Bible is true and reliable. Of course, there are those who wonder how Adam and Eve could have lived tens of thousands of years apart.
This is, of course, nonsense. This discovery in no way means that there was only one woman 140,000 years ago or only one man 60,000 years ago. On the contrary, there must have been many women and many men living at the same time, only that their mitochondrial genes and their Y chromosome genes were not inherited to the present. But they or they inherited other genes. It is likely that “Mitochondrial Eve” and “Y-chromosome Adam” inherited no genes other than their mitochondria and Y chromosomes to the present day.
It is not only the mitochondrial genes or the Y chromosome that are in this situation. If we take any gene and trace its mutation far enough back, we can always find a common ancestor, except that these ancestors may have lived at different times. These ancestors may not even be human; some may go back to some animal before man evolved.
The reason this is a statistical artifact, so to speak, is that the further back you go, the more ancestors each person has: you have two parents, four grandparents, eight great-grandparents …… If you double that, it becomes an astronomical number after a few dozen generations. But the number of people in each generation is fixed, in fact, the earlier the number will be smaller, so if you go back far enough, all the people who lived at that time and before that time and still have descendants today will become your ancestors, and so on, and so on, for everyone.
So, if we go back in time with a characteristic common to all people in the world (such as a mitochondrial gene, Y chromosome, or a gene), eventually all people in the world will find a common ancestor, but this does not mean that there were no other people at that time, nor does it mean that this old ancestor’s genetic contribution was greater than that of all other contemporaries.
It is easy to understand the analogy with the genetics of the surname. We take the Fang family tree generation by generation to count forward, and finally found the Fang family ancestors, but this does not mean that all the genetic heritage of the Fang family only from the Fang ancestor couple, in the thousands of years of the evolution of the Fang family, constantly joined the blood of foreign families, and these people’s blood, can be traced back to the same period with the Fang ancestors, some of these people, the contribution of the Fang family lineage, perhaps even more than the Fang ancestors.
However, when we take the “Fang” surname as a symbol to study the Fang family blood, the blood from these foreign surnames are ignored.