first woman
Mitochondrial Eve is a traditional molecular biological concept that refers to the female, the oldest common ancestor of modern humans (Homo sapiens). Humans inherited one of two types of genomes from it – mitochondrial.
Humans have two types of genomes: nuclear and mitochondrial. The first is widely known to everyone – this is the genome located in the cell nucleus and subjected to recombination and reduction during the formation of reproductive gametes (egg and sperm), that is, grandchildren receive half of the genes from the father, and the other half from the mother.
The other genome is found only in mitochondria, which are passed on to offspring via the egg, meaning it is strictly maternally inherited.
“Mitochondria are the inner parts of the cell; They are small ellipsoidal structures surrounded by a protein-lipid membrane floating in the cytoplasm. These are also called organelles. Each mitochondrion has its own small-loop haploid double-stranded DNA – the mitochondrial genome itself is about 16,560 nucleotides in size, which is 181 thousand times smaller than the nuclear genome, which contains about 3 billion nucleotides. The mitochondrial genome contains 37 genes, including several very important genes responsible for energy metabolism. If there are violations in this genome, then we will suffer from a serious hereditary disease that will be transmitted through the mother. However, unlike the nuclear genome, which has only one copy, the mitochondrial genome has many copies, because the cell contains not just one mitochondrion but several hundreds or even thousands of mitochondria. Therefore, if a mutation occurs in one organelle, this is compensated by the others. These mutations are not as dangerous as mutations in nuclear DNA,” Professor Krutovsky explained to socialbites.ca.
The main function of these organelles is to synthesize ATP (adenosine triphosphate), which is used as the main source of chemical energy in the cell. Mitochondria are often referred to as the “energy factories” of every cell of eukaryotic organisms, including humans.
“Unlike nuclear DNA, which we receive half from mothers and the other half from fathers during the fertilization of the egg, mitochondrial genes, located in an organelle that is an intracellular structure, are transferred to all individuals in the mother’s lineage only with the egg. When the sperm nucleus combines with the egg nucleus, there are tens of hundreds of mitochondria around the nucleus. The geneticist noted that these were transferred from mother to child.
Therefore, mitochondrial DNA has strictly maternal inheritance, so the mitochondria that we now have in our cells can be traced along the maternal line: from the mother to the grandmother, to the great-grandmother, and so on to the first ancestor, mitochondrial Eve.
It turned out that he was the ancestor of all descendants of modern humans on Earth.
We are all African
There are phylogenetic analysis methods used to determine evolutionary relationships between organisms. The results of the analysis can be plotted in a diagram called a phylogenetic tree.
“Mitochondrial DNA, like any other, mutates, and the number of these mutations increases as the time distance between generations increases. By analyzing individuals of different geographic, ethnic and racial origins, geneticists have created a phylogenetic tree that reflects the time when generations diverged from a common main ancestor. When you look at it, it is reversed.” You can see the maternal phylogenetic tree, which resembles a family tree.
This shows that we are all related and have a common maternal ancestor in Africa; Our grandmother was also there. This single ancestor was figuratively called the mitochondrial Eve,” Krutovsky explained.
According to today’s known scientific data, modern humans emerged in Africa approximately 200 thousand years ago, and began to spread throughout the world in waves through Asia and Europe in the last 70-100 thousand years. This path of human migration can be clearly traced through the phylogenetic tree. Since the frequency of genetic mutations is relatively constant, scientists can understand from their numbers when the divergence from ancestors occurred, in what years people settled: some went to Europe, others to Asia.
“Most of the worldwide migrations and dispersal of Homo sapiens have occurred in several waves over the last 50-60 thousand years; However, the first exodus from Africa may have occurred even earlier, around 70-100 thousand years ago. 15-20 thousand years ago, North America began to be settled over the Bering Strait (more precisely, a “bridge” since it was land at that time), and then South America began to be settled about 10-15 thousand years ago. The ancestor of all humanity lived in East Africa about 120 thousand years ago. But this does not mean that he was literally the only person who existed in his time, or that he was the only representative of his time and place. This is just a hypothetical common ancestor whose genes were passed down the maternal line to modern humans,” Krutovsky concluded.
Each of us has the genes of the mother of all mothers (mitochondrial Eve), albeit in a slightly modified (mutated) form.