Illustration of Mitochondrial Eve

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Mitochondria, the fundamental part of a cell which supplies the most of the chemical energy by generating ATP, also gives extremely valuable clues about the human genome. Since it is inherited maternally, all human beings on the earth could be traced back to an individual female lived in Africa who is called “Mitochondrial Eve” and  by the scientists. A recent study of scientists from Rice University suggests that our common “grandma” lived 200,000 years ago. Fascinating story.

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The most robust statistical examination to date of our species’ genetic links to “mitochondrial Eve” the maternal ancestor of all living humans confirms that she lived about 200,000 years ago.

Artist's cross section of a mitochondrion
The Rice University study was based on a side by side comparison of 10 human genetic models that each aim to determine when Eve lived using a very different set of assumptions about the way humans migrated, expanded and spread across Earth.

The research is available online in the journal Theoretical Population Biology.

“Our findings underscore the importance of taking into account the random nature of population processes like growth and extinction,” said study co-author Marek Kimmel, professor of statistics at Rice. “Classical, deterministic models, including several that have previously been applied to the dating of mitochondrial Eve, do not fully account for these random processes.”

The quest to date mitochondrial Eve (mtEve) is an example of the way scientists probe the genetic past to learn more about mutation, selection and other genetic processes that play key roles in disease.

“This is why we are interested in patterns of genetic variability in general,” Kimmel said. “They are very important for medicine.”

Using mitochondrial genomes to gauge relatedness is a way for geneticists to simplify the task of finding common ancestors that lived long ago. That is because the entire human genome contains more than 20,000 genes, and comparing the differences among so many genes for distant relatives is problematic, even with today’s largest and fastest supercomputers.

But mitochondria — the tiny organelles that serve as energy factories inside all human cells — have their own genome. Besides containing 37 genes that rarely change, they contain a “hypervariable” region, which changes fast enough to provide a molecular clock calibrated to times comparable to the age of modern humanity. Because each person’s mitochondrial genome is inherited from his or her mother, all mitochondrial lineages are maternal.

To infer mtEve’s age, scientists must convert the measures of relatedness between random blood donors into a measure of time.