By a Newsnet reporter
Researchers at the University of Edinburgh have identified a gene which apears to have played a crucial role in human evolution. The gene, miR-941, could shed light on how our distant ancestors learned to use tools and language.
The gene is one of those which is unique to humans, and which doesn’t occur in our closest relatives, chimpanzees, bonobos and gorillas. Humans share over 98% of our genes with chimpanzees. miR-941 is the first gene occurring in humans but not in great apes whose specific functions have been identified.
The gene is active in two regions of the brain which control decision making and language skills. The gene is also thought to be involved in the remarkable longevity of humans. Humans can reasonably expect – barring accidents or infections – to live longer than 70 years, this is much longer than is typical for a mammal species of our size.
A longer life span would have been extremely useful to our early ancestors, as older members of the community act as repository of learning. This means that new generations were less likely to have to relearn everything about their environment from scratch and aided in the development of human culture. Amongst hunting gathering peoples, older members of the community are often experts in skills such as tool making or knowledge of plant and animal resources and are able to pass their knowledge and skills to younger people. In a short lived species, this knowledge is more easily lost.
Dr Martin Taylor, who led the study at the Institute of Genetics and Molecular Medicine at the University of Edinburgh, said that the gene probably emerged between 1 million and 6 million years ago, after the evolutionary line ancestral to modern humans had diverged from the line which gave rise to chimpanzees.
Dr Taylor said:
“As a species, humans are wonderfully inventive – we are socially and technologically evolving all the time.
“But this research shows that we are innovating at a genetic level too.
“This new molecule sprang from nowhere at a time when our species was undergoing dramatic changes: living longer, walking upright, learning how to use tools and how to communicate.
“We’re now hopeful that we will find more new genes that help show what makes us human.”
Most differences between species are believed to occur as a result of mutations to existing genes, or the duplication and deletion of genes. However the Edinburgh team say that miR-941 emerged as a fully-functional gene out of previously non-coding genetic material – previously termed ‘junk DNA’ as early geneticists were unable to figure out what purpose these genes served. It is now thought that most so-called ‘junk DNA’ performs regulatory functions, by switching other genes on or off.
The evolution of gene miR-941 is thought to have occurred a brief interval of evolutionary time. Until now, it has been remarkably difficult to see this process in action.
The ancestors of humans are believed to have lived in East Africa where they diverged from the ancestors of modern chimpanzees and bonobos (or pygmy chimpanzees) around 6 million years ago. Human ancestors evolved upright walking and over time their brain size became much larger. The early human line diverged into a number of species which have since become extinct.
Some of these early human species migrated out of Africa, where they eventually evolved into Neandertals in Europe, a little known species called Denisovans who lived in mainland Asia, and the dwarf species known as the ‘Hobbit’ recently discovered in Indonesia.
Modern humans descend from early humans who remained in Africa. Fully modern humans first appear in the African fossil record from around 150,000 years ago. Our ancestors migrated out of Africa around 80 to 100 thousand years ago, and drove the older species into extinction. Recent genetic work has confirmed that all humans outside Africa carry a small proportion of genes from Neandertals and Denisovans, proving that our African ancestors interbred with the older populations they encountered when they migrated into Asia and Europe.