Scientists have successfully identified the genes responsible for the evolution of human bipedalism, which enabled our ancestors to walk upright approximately 6 million years ago.
About the study: Published in the journal Science, the study not only shed new light on the genetic basis of one of humanity’s defining physical features but also revealed subsequent risk of arthritis in humans.
The research team, composed of experts from Columbia University and the University of Texas, focused on pinpointing the specific genetic variants that brought about the adaptation of walking upright on two legs by combining deep learning and genome-wide association studies.
Mapping human skeletal changes: The researchers trained a deep learning algorithm to analyze over 30,000 full-body X-rays from the UK Biobank, an extensive online database of medical and lifestyle records from hundreds of thousands of Britons.
After having the algorithm standardize the X-rays and precisely measured many skeletal features from the data, they then scanned the human genome for select chromosomal regions linked with variations in 23 important skeletal measures. Through the analysis, the scientists were able to map the genome regions that are responsible for the skeletal changes in primates that led to upright walking, as supported by natural selection.
Study co-author Vagheesh Narasimhan, an assistant professor of integrative biology at the University of Texas in Austin, said: “What we’re seeing is the first genomic evidence that there was selective pressure on genetic variants that affect skeletal proportions, enabling a transition from knuckle-based walking to bipedalism.”
Links to arthritis: The scientists were able to identify 145 key points in the genome responsible for controlling skeletal proportions, which they found to be associated with hip, knee, and back arthritis.
Arthritis, which involves inflammation or swelling
of one or more joints, characterizes over 100 conditions that affect the joints, tissues around the joint, and other connective tissues.
The study found that individuals with higher ratios of hip width to height were more susceptible to hip osteoarthritis and pain, while those with higher thigh-bone-length-to-height ratios were at greater risk of developing knee arthritis and knee-related issues. Similarly, individuals with a higher ratio of torso length to height faced an elevated likelihood of experiencing back pain.
Tarjinder Singh, co-lead of the study and assistant professor of computational and statistical genomics at Columbia University Vagelos College of Physicians and Surgeons, noted that such findings potentially open the door to improved prediction of a patient’s risk of developing arthritis in the future.