At the head of the research carried out for the genographic project of IBM and National Geographic were two Israelis - Dr. Doron Bahar from Rambam and Dr. Sahron Rost from Tel Aviv University * The climatic conditions separated the two populations, one of which spread throughout the world and gave birth to most of the humans today And from the second, the Koi and the San remained in the southern continent of Africa
Dr. Doron Behar, a geneticist from Rambam Hospital and Dr. Sahron Roset, a statistician from Tel Aviv University and IBM's "Watson" research center in New York, conducted their research as part of the genographic project shared by National Geographic and IBM. The project attempts to describe processes in the spread of human populations throughout the planet through genetic research. Their research was published last Thursday in the American Journal of Genetics.
The scientists claim that the most likely scenario is that the two populations separated at the beginning of the evolutionary path of the human species. This is how the population that lived in South Africa split from the one that lived in the east of the continent for 50 to 100 thousand years. The split could have been caused by climate change. New studies of climate data have suggested that East Africa went through a series of major droughts between 135 and 90 thousand years ago. "It is possible that extreme environmental conditions and a changing climate caused populations to migrate to other places in order to improve their chances of survival." Dr. Behar said. Once such a population arrived in South Africa, it was separated from its source population by the drought events that occurred in the area that spread between them.
A history book in the human body
The research is based on testing the mitochondrial DNA of African residents. Mitochondrial DNA is hereditary material found in organs located in the cell fluid and involved in energy production through metabolism. This material is particularly effective in tracing the history of the development of the human race. Two characteristics make it so. First, it is a matter of hereditary material that passes to the offspring from the mother and not from the father. If you want to check, for example, whether two people were born to the same mother, it is enough to take samples from the mitochondrial DNA found in one of their body cells and compare the samples. Since the DNA is not affected by the father's inheritance, the result will be unequivocal. When scientists are asked to check the origin of entire populations, the absence of inheritance from the father cuts the amount of information to be taken into account in half and makes the testing process infinitely easier.
In addition, the rate of mutation formation in mitochondrial DNA is 20 times greater than in the DNA found in the cell nucleus. Mutations are changes in the molecular composition of DNA, which may indicate environmental changes that required adaptation of the species to new conditions. Also, counting the number of mutations that have occurred in a molecular composition allows scientists to count the number of generations that have passed since the hereditary transfer of DNA began. That is, the multitude of mutations in mitochondrial DNA makes it an effective historical source for the study of human history. This genetic material can tell us how many generations have passed since two people on different sides of the world shared a single mother. It can also indicate a decisive ecological change, which caused the formation of some kind of mutation.
separated dynasties
Until now, when scientists investigated the genetic origin of populations, representative sequences of several hundred bases from the mitochondrial DNA were examined. In the present study, the entire total sequence, approximately 16.5 thousand bases, was examined. This is in order to reach a higher level of accuracy and a better ability to separate between the groups. The test among the Koi and San tribes revealed that 70% of the tribe's members are descendants of the oldest maternal dynasties in the world. These dynasties, known as L0D and L0K, are approximately 200 thousand years old. 30% of the members of the tribes are the offspring of maternal lineages common to all humans on the African continent.
In the second step, the researchers compared the amount of mutations that differentiate between the old lineages and lineages found among the rest of the inhabitants of Africa, and between them and the lineages found among the rest of the San and Koi. "We looked at the differences from both directions," says Dr. Behar in a conversation with the Hidaan website. "We discovered an interesting thing. When we compared the DNA of the old lineages to the DNA of the closest lineages, however rare they may be, which are still found in other populations in Africa, from the calculations of the number of mutations that separated the lineages, we discovered that they converged together no more than 40 thousand years ago. This means that the first time there was any gene flow from the Koi and San people out was about 40 thousand years ago at the most.
From the other direction, we examined the pan-African lineages of the Kui and the San, that is, the 30% that do not belong to one of the ancient lineages. We saw that the first time these lineages entered the genetics of the Koi and San people was also about 40 thousand years ago." That is, the human race has existed for about 200 years, but the Kui and San people began to share genetic baggage with the rest of Africa's inhabitants only about 40 years ago.
To examine the third part of the equation, when the split between the dynasties occurred, the researchers used a statistical method developed by Dr. Sahron Rost, a statistician from Tel Aviv University. "We developed a new statistical method based on a permutation test," explains Rust in a conversation with the science website, "when you want to know the probability that some process has occurred, you calculate the probability of each event in the process occurring. If we reached a small percentage it means that the event is surprising and if we find too many surprising events it means that something in the script we built is not true. This way you can examine the question of when the split happened. If we assume that the split happened 70 thousand years ago, the result is unlikely, the conclusion is that the split should have happened earlier."
Rust's method indicates that the split between the San and Koi tribes and the rest of the African population occurred 90-150 thousand years ago.
"To summarize the results of the study" says Behar "we suggest that the human race moves in small groups and not as one homogeneous group that spread continuously in Africa. We see evidence of such a split in the period 90-150 thousand years ago, we see that this split could have been maintained for up to 100 thousand years, until the mixing of genes started again."
to discover the secrets of the past
Behar and Rost's research, as mentioned, was conducted as part of the genographic project (a term that combines genetics and geography). As part of the project, hundreds of thousands of blood samples are collected from people around the world and analyzed by advanced IBM systems. The purpose of the project is to conduct a comprehensive mapping of the genetic relationships between different ethnic groups in the world, in order to answer fundamental questions concerning the spread of the human race. Among the questions waiting to be answered: Do all human beings trace their ancestors from Africa or did humans develop at different points in the world? If man indeed originated in Africa, when did humans first leave there?
Rust sees participating in the project as an important mission: "For me as a person who is interested in data, in drawing conclusions from data, in particular scientific data - this is the fulfillment of a dream to work on interesting data, on interesting problems, to explore human history through the analysis of genetic data and to discover conclusions about the shared distant past of All of us."
Spencer Wells, director of the genographic project for National Geographic and IBM, is thrilled with the results. "This study illustrates the power of genetics, which is able to reveal decisive events in the history of the human race. Tiny bands of ancient humans, separated by the harsh living conditions, return and unite when they are on the verge of extinction, in order to return and colonize the entire planet. What an epic drama!”
In his words, Wells was referring to the theory that has existed for some time, which hypothesizes that the human race was already on the verge of extinction at the beginning of its time and returned to multiply and intensify in the late Stone Age. Some researchers believe that the human population was reduced at one point to about 2,000 people. Wells believes that the severe droughts, which caused the split in question, are what brought the human race to the brink of extinction.
(Avital Lahav, YNET also participated in the preparation of the article)
32 תגובות
We are expected in the next 4000 years to have climatic problems and famine and must give strong brakes like China (2 genetically modified children a boy and a girl at most!)
I saw a film about our genetic history in the last 100,000 years.
The genetic gap between the Asian, African, and white race (and more) is no more than 34,000 years old, for example between the Asian and the black. If we look at the external gaps only:
The color of the skin, the flattened nose of the Asians, the slanted eyes perhaps due to the shedding of the skin to protect against the cold, the short height. These are significant differences that were created over a short period of time. You don't need a million years. It is true that all races can breed with each other. The geographical separation was not enough to block it. Not enough time has passed in disconnection.
When there is a significant genetic gap between an ancestor and a new species, the ability to reproduce between the species usually ceases. Reference is made to the book "Almost Like a Whale" by Steve Jones, and other popular books by Richard Dawkins for example. He refrains from mentioning that a cognitive gap may have arisen because it led to race theories. A huge cultural gap was created between the races, most of which is probably responsible for the gap between the continents.
Immaterial amendment:
The frescoes from the Lesco caves They are only 16000 years old but there are Findings of art already from 40000 years ago
Of course, when I wrote maternal DNA above, I meant the mitochondrial one
For the archaeologist:
I don't understand what this discussion is about.
It is clear that those who are tested today are humans.
What were their ancestors (actually their mothers) 150000 years ago and whether they can be classified as HSS or not was not tested in this study and of course it was not allowed to test it at all based on the maternal DNA alone.
It is clear that the meeting between the populations - the one that took place 50000 years ago was already between creatures that were very similar to us (the wall paintings from the Lesko caves are approximately 40000 years old).
In any case, these are creatures that are all on our path of development.
The earliest evidence of AMH is from 160 thousand years ago
archaeological
why not? We have existed for about two hundred thousand years.
150 thousand years, leaving Africa is probably not about HSS...
Homo sapiens sapiens of course
The article does not specify which types of hominids are involved. If anyone has the answer, I would appreciate it if you would
There are people whose misunderstanding is superior to the "understanding" of others
Avi:
In the middle of writing my last response, I had to drive one of my sons to the train (there is no public transportation in the Ramots of the Shaviv), so I didn't see your response until after I sent my response.
thanks for the effort.
Dr. Behar's explanation really aligns with my understanding of the article and emphasizes how the matter is not simple.
Thanks again.
Well, after reading the article it is of course much easier to understand what they did.
As Roy said, the research looks even more impressive with this understanding.
However, I would not describe the process as simple calculus described it (although it may have intended the correct description) because this description is "blind" to the difference between "the number of mutations" (which may also be a function of the number of people) and "the number of mutations in a single cell". He must also make assumptions about the chance of the same mutation between the two groups when what is interesting here (and the chances of it being the same in both groups are astronomically smaller than the chance of the same mutation) is an identical series of mutations.
Even with the expansion I have given so far, the explanation is not complete because it is certainly possible that between the groups migrated at a later stage humans whose most ancient common mother predates the time of the meeting of the groups and the only way to find this out is by finding out how "full" their mutation tree is.
It is recommended to read the full article.
For Michael (13) from my conversation with Dr. Behar, I understood that they can tell when the Pan-African lineage penetrated into the Koi and the San by the frequency of mutations. They took San people who have foreign lineages and tribesmen where these lineages are common and compared.
In addition, they compared the lineage common in the San with related, albeit rare, lineages found in other tribes to understand when the San first contributed their own maternal genes to other tribes. In both cases they reached the same answer - about 40 thousand years.
The third part - when the early split happened was more difficult to discover and it is a fact that the range is very wide (90-150 thousand years ago), and here they had to use more computers and statistical programs (and this is the part of Rust).
For Roy, despite IBM and all the cooperation, it was necessary to complete a lot of manual work in the construction of the tree.
Thanks.
I must point out that the answer is not as simple as it may seem. It's amazing to think how much computing power must have been invested to analyze all the hundreds of thousands of mitochondrial DNA samples and find the subtle connections between them.
Kudos to the Israeli researchers for the ambitious and successful project.
For the shepherds of Cezana
I will slightly refine my father's correct explanation.
The time elapsed since the union between groups of people can be measured according to the mutations that have occurred in the donated mtDNA lineages from the moment of the donation onwards.
mtDNA lineages are "associated" with the group of people that contains the greatest variety of its mutations (hereafter, the donor group), for example - members of the Zulu tribe.
It is assumed that the rate of mutation creation is constant (information about this rate can be found on the attached website) and from this it can be concluded from the number of mutations observed in the recipient group (but not observed in the donor group) about the time that has passed since the union.
The chance that a mutation will occur in both groups is very low compared to all the relatives who were included in the above calculation anyway.
Michael, if the original number of foreign women was small, there is no need to test too many people, if they maintained the tribal character for a long enough period, then there should be a very limited number of lineages in each tribe.
I have a vague idea.
If a person belongs to the tribal population it can be distinguished by his normal DNA.
There are differences in the mitochondrial DNA only according to the women's lineages, which means I can build a mitochondrial DNA lineage tree only of the people of the tribes (any mother who had two daughters will create a possible split in the tree!) So I have to locate when the first splits occurred in the mitochondrial DNA of the people of the world The external in the tribal people (identified by the normal DNA), which is a possible dating process according to the research.
Dates of several ancient dynasties should give a good estimate (the number cannot be too large because the world population was very small).
It makes sense to me, what do you think?
expansion:
I can think of a way that is based on testing a very significant percentage of the population, but I find it hard to believe that this is what they did.
Avi:
Although I haven't read the article yet, it's hard for me to say that I understood your explanation.
How, based on the comparison you offer, do you know when the isolation ended?
Thanks.
The scientific article
The answer is simple, you don't see a union of lineages, you see that the population has a certain percentage of people who carry mitochondrial DNA from different lineages than the main lineage. These lineages are compared to their relatives in other tribes and thus know approximately when they began to infiltrate the tribe under investigation.
Indeed an interesting article.
simple calculation -
I would appreciate it if you could explain to me and the readers how you can distinguish the association of lineages according to the mitochondrial DNA. At first glance, and according to simple logic, it seems that there should not be such an association, since mitochondrial DNA is only passed from a mother to her daughters (and of course also to her sons, but they do not pass it on) ). Since two women cannot have a child on their own, Michael's question seems very interesting to me.
Thanks,
Roy.
Michael's question seems really brilliant to me. Does anyone know the answer?
Simple account:
Just for clarification:
The name "simple account" is a name originally intended to mock others, so I was never surprised by the content of your comments.
I didn't ask your opinion about me or my approach, nor did I ask how simple the answer is.
I only asked what the answer was.
I don't think you have a simple answer to the question, but if you do, I suggest you write it for others as well.
Personally, I would consider the fact that you do not write the answer as evidence that you do not know it
And further proof of your contempt for others.
Know that the "answer" you originally gave I thought about before formulating my question and simply saw that it did not explain anything.
The answer to your question is very simple
But neither you nor your attitude pleases me.
Simple account:
come on!
And how do you know how long the lineages in the same population?
It is interesting what anatomical differences there are between the Kohi-San tribes and the rest of humans (besides, of course, an extremely short stature) and even more interesting is the question, which of the anatomical differences are 200000 year old remnants and which are late adaptations.
To Michael,
Of course, a person with two mothers is not required. It is enough to find two (or more) lineages in the same population.
Asaf:
I don't want to call Joel at this time just to ask him, but is there any support for your claim that Homo Sapiens was found here 125000 years ago?
Avi:
Is it possible to get a link to the original article or a reference from the Israeli researchers to the following question:
I understand how to calculate the time of the distribution of maternal lineages, but I do not know how to calculate the time of their re-convergence. Is there any significance to the reunion of maternal dynasties? After all, in order to gather, a person who has two mothers is needed, isn't it?
It is indeed interesting and instructive, the possibility of the extinction of the human race before the Stone Age
Gives validity to the contingencies why we are here,
The only question that arises is how most of the studies that lead to the assumption are reconciled
The "exit from Africa" before the Stone Age - about fifty thousand years ago,
How does this assumption fit if the findings of Homo sapiens in our immediate environment,
Findings that are estimated to be one hundred and twenty thousand years old?
An excellent, comprehensive and interesting article with many basic concepts that are well explained to fans of popular science.