The study of fine-haired mammoth gene changes the theory of evolution

A major genetic study of the recently extinct woolly mammoth reveals that they are not a homogenous large group and do not have the same high genetic diversity as previous scientists. think.

Stephan C. Schuster - associate professor of biochemistry and molecular biology at Pennsylvania State University and leader of the research team - said: ' The mammoth population is divided into two groups, one of which extends way. This is 45,000 years long before the first human appearance. This discovery is particularly interesting because it rejects human hunting that causes mammoths to become extinct, instead climate change and disease are the most likely causes of extinction. ' . The discovery was published this week in the online edition of Proceedings of the National Academy of Sciences (PNAS).

The study marks the first time scientists have analyzed the entire structure of extinct mammoth populations using the mitochondrial genome - the DNA that makes up all the genes in the structure. mitochondria of cells. The data obtained from the study allowed a new hypothesis to be tested by the group: There are two groups of fine feather mammoths. This is a hypothesis that has not been previously recognized by fossil studies.

Fur tufts of mammoths preserved in frozen soil have a thick outer shell and thin fur underneath.(Photo: Stephan Schuster Laboratory, Pennsylvania)

Scientists analyzed genes in the hairs of individual mammoths - extinct elephants adapted to the icy environment in the northern hemisphere. People found mammoth bodies everywhere in the vast area of ​​northern Xiberia. Their extinction period spread over 47,000 years, from 13,000 to 60,000 years ago.

Schuster and Webb Miller - Pennsylvania state professor of biology, science and engineering - led the international team. Participants also have Thomas Gilbert of Copenhagen University (Denmark) and other scientists from Australia, Belgium, France, Italy, Russia, Spain, Sweden, the United Kingdom and the United States. The team consists of experts in the field of gene evolution, ancient DNA, paleontology - mammoths, and other curators of various natural history museums.

An important finding to understand the extinction process is that individuals of each mammoth group are closely related. Miller said: ' The phenomenon of genetic separation is surprisingly low by the extremely large range of mammoths: from Western Europe to Bering Cape in Xiberia, to North America . That phenomenon may have reduced the biological adaptability of elephants at a time when environmental changes accompanied other challenges. '

Miller added: 'Our study found that genetic separation in two mammoth groups occurred more than a million years ago, by a quarter of the genetic distance between Indian elephants and European elephants. Africa and mammoth '. The diversity in mammoth populations centuries ago is very low as it is in African elephants in South India today.

According to Schuster, 'low genetic segregation in the South Indian elephant population is said to contribute to the maintenance of a prosperous elephant population' . The researchers' mitochondrial genome has been found to be several times more complete than the mitochondrial genome of both the Indian elephant population and the present-day African elephant .

While previous studies only conducted short DNA fragments of extinct species, the new study found and compared 18 complete genomes of extinct mammoths with intact mitochondrial DNA. important material to learn ancient genes. This achievement is based on an earlier discovery led by Miller, Schuster and co-author Thomas Gilbert, who published last year the viability of ancient DNA in hair better than any other tissue that was distributed. calculus so far. Since then, hair and hair have become the most effective sources of DNA to study the genetic sequence of extinct animals. Furthermore, large mammoth feathers can be found in cold areas. It is not considered to be a valuable fossil material like bone, muscles also carry anatomical information.

(Photo: Mammuthus lab Khatanga / Tom Gilbert)

"We also discovered that DNA in the hair shaft contains a significant amount of mitochondrial DNA - a special type of DNA that is often used to determine the genetic diversity of a population, " Miller said. Previous research by the team also demonstrated that hair has superiority when used in molecular genetic analysis due to easier hair removal than bone. Fur not only easily cleanses outside bacteria or fungi, but its structure also protects it from decay, preventing microorganisms from entering the environment.

Hair samples were stored in many different museums for many years before researchers took them, but they still got a lot of useful DNA. Schuster said: 'One of our analysis samples was from the famous Adams mammoth discovered in 1799. The feather pattern was preserved at room temperature for the last 200 years'. This research technique has opened a new door for future projects aimed at interesting specimens collected long ago and no longer exist in modern species. Even molecular analysis of the entire sample can be carried out, this is the technique the team calls ' Museomics ' .

Schuster said: 'We plan to continue using our techniques to answer the secrets of populations that existed long ago to understand what is needed for their existence. Many of us have a particular interest in finding out as much information as possible about the extinction process of a large mammal. '