The Genetic Changes that Allowed Humans to Walk Upright
Perhaps the most significant advance in primate evolution occurred about 6 million years ago, when our ancestors began to walk on two legs.
The Transition to Bipedal Locomotion
It is believed that the gradual transition to bipedal locomotion allowed primates to better adapt to different environments and freed their hands to use tools, which in turn accelerated cognitive development. These changes paved the way for modern man.
Uncovering the Genetic Changes
The genetic changes that made the transition from articulated running to walking upright possible in humans have been uncovered in a new study by scientists at Columbia and Texas Universities.
Scientists have discovered the genes that gave humans the ability to stand and walk upright about six million years ago. They believe these genes have shaped the human skeleton over tens of thousands of years, “from the width of our shoulders to the length of our legs.”
Implications for Arthritis
In a paper published in the journal Science, the team identified variants (permanent changes in the DNA sequence) associated with arthritis, potentially opening the door to a future where doctors can better predict a patient’s risk of developing arthritis.
“On a practical level, we have also identified genetic and skeletal variants associated with hip, knee and osteoarthritis, the leading causes of adult disability in the United States,” said Tarjinder Singh, assistant professor of computational and statistical genomics at Columbia University College of Physicians and Surgeons and co-lead of the study.
Bipedalism: Humanity’s Defining Physical Feature
The ability to walk upright, known as bipedalism, is one of humanity’s defining physical features.
Using a combination of deep learning (a form of artificial intelligence) and genome association studies, scientists at Columbia and Texas Universities have created the first map of the genomic regions responsible for structural changes in primates that lead to upright posture. The map shows that the genes underlying the anatomical changes seen in the fossil record were heavily influenced by natural selection and gave early humans an evolutionary advantage.
Analyzing X-rays and Genome-wide Association Studies
In the study, the team analyzed more than 31,000 full-body x-rays from the British Biobank, an online database of medical and lifestyle records for more than half a million Britons.
The team then used an approach known as genome-wide association studies, in which they identified genes associated with a particular condition or trait to identify regions in the genome, the complete set of DNA associated with the human skeleton.
Scientists said they found 145 points in the genome that control the size of the skeleton.
Evidence of Selective Pressure
“What we’re seeing is the first genetic evidence of a selective pressure on genetic variants that influence skeletal size to allow for a transition from knuckle-walking to upright posture,” said Vajesh Narasimhan, assistant professor of integrative biology at the University of Texas at Austin, USA.
Associations with Joint Disorders
The team also found that people with a higher hip-to-height ratio were more likely to suffer from osteoarthritis and hip pain.
Those with a higher hip-to-length ratio were more likely to develop arthritis in their knees, knee pain, and other knee problems.
The team said that people with a higher torso length-to-height ratio are more likely to develop back pain.
“These disorders develop due to lifelong biomechanical stress on the joints,” said Ecorust Kuhn, a graduate student in biochemistry at the University of Texas at Austin and lead author of the paper. “Skeletal proportions affect everything from how we walk to how we sit, and it makes sense that they are risk factors for these disorders.”
Source: Independent
