A lizard-like animal that lived in the Permian 289 million years ago suffered from a disease of bone metabolism similar to the Paget's disease in modern humans. This is by far the oldest known evidence of such a disease and the oldest indirect evidence of a viral infection.
The animal in question belonged to an extinct group of lizard-like creatures called varanopidae, relatives of the earliest ancestors of reptiles and mammals. The study authors identified the disease using two fused tail vertebrae from a sub-Permian cave near Richards Spur in Oklahoma, USA. The application of Micro-CT at the Museum für Naturkunde Berlin allowed the investigation of both the outer and inner structure of the fused bones and showed that the bone had become very thin in places due to abnormally high degradation, while excessive bone growth in other places had led to an abnormal thickening of the bone and ultimately to the fusion of the two vertebrae.
The researchers pointed out that this finding is highly similar to Paget's disease. This is a bone metabolism disorder characterized by the breakdown of coordination between bone-forming and bone-degrading cells (osteoblasts and osteoclasts). Paget's disease is well studied in humans and mostly affects the hips and spine. It has also been diagnosed in other modern mammals and reptiles. A few years ago, Paget's disease was also diagnosed in a dinosaur from the Jurassic period by researchers from the Berlin Natural History Museum. Both genetic factors and measles-like viruses are involved in the outbreak of this disease, although their exact trigger is still controversial.
Since only two vertebrae are preserved from the diseased individual, it is impossible to determine to what extent the disease also affected other parts of the skeleton. If it was limited to the tail only, the animal had probably only slight pain and stiffening of the tail.
The discovery of this bone disease in a varanopid is the earliest known evidence of Paget-like bone disease and suggests that the susceptibility to such diseases was already present in our early sub-Permian relatives. It is also possibly the oldest indirect evidence of viruses in the Earth’s history.