Comparing the genomes of hundreds of mammals has pinpointed the crucial regions that set humans apart from other species and that contributed to our unique qualities, such as our ability to walk upright, communicate in complex ways and develop sophisticated technology.
An analysis of the genomes from 240 mammalian species, including humans, chimpanzees and gorillas, has found more than 5,000 “accelerated regions”—where evolution occurred particularly quickly—in the human lineage that likely contributed to our special traits. These regions include genes that influence human-specific characteristics, such as the shape of our skulls, our ability to produce speech, and our resistance to HIV infection.
The comparison of mammalian genomes also provided insights into evolution, revealing that mammals that live more varied lifestyles tend to evolve faster, while species that specialize in a narrow range of activities evolve more slowly.
“Now that we have 5,000 of these regions in hand, we can start to focus on what the specific molecular mechanisms are and which particular genes are responsible,” said Dr Ryan Gutenkunst of the University of Arizona in Tucson, who worked on the study, published in the journal Nature.
The work was part of the Mammalian Genome Project, an international effort to sequence and compare the genomes of the world’s mammals, aiming to shed light on mammalian evolution and help scientists understand human health and biology.
“It gives us a tremendous foundation and starting point for the exploration of human evolution and the biology that makes us uniquely human,” said Dr Webb Miller, a professor of biology and computer science at Penn State University who led the research team.
“What’s really new and interesting about this study is the focus on the accelerated portions of the genome,” said Dr Tomàs Marques-Bonet of the Spanish National Research Council, who also worked on the analysis.
The results indicate that most evolutionary changes over long time periods occur gradually and have small effects, but that dramatic changes, such as those involved in the evolution of primates, can happen rapidly over “geologically short” periods of a few million years.
The discovery of many more of the accelerated regions involved in the evolution of the human lineage will also help scientists pinpoint which DNA changes were linked to the onset or acceleration of debilitating genetic diseases, such as cancer, diabetes and neurodegenerative conditions, Dr Miller said.
He said the data on the accelerated regions had already revealed, for example, that certain immune system genes and DNA repair mechanisms had undergone particularly rapid evolution in primates.
“The most unexpected finding was that all of these accelerated regions collectively are about five per cent of the genome, which is far more than we ever imagined,” Dr Miller said.
Dr Miller said he hoped the data would help scientists better understand how human evolution has shaped our response to different environmental conditions and selective pressures.
“You look at the human species, and you see incredible variation, not just between species, but also within species,” he said.
“We’re much more variable in terms of our immune systems, our physiology, our behaviour and our cognition than other species.
“What is special about humans is our remarkable capacity to adapt to new environments and to survive under an enormous variety of conditions.”
