The TDTOP reported that Mabuya lizards dwelling in the Colombian Andes mountains possess unique characteristics that set them apart from other reptiles. While most reptiles lay eggs with tough shells, certain species of Mabuya give birth to live offspring. What makes this even more fascinating is that these lizards have developed placentas, specialized organs for nourishing their developing young inside their bodies.
Placentas are typically associated with mammals like mice and humans, as we belong to the category of placental mammals. However, other animals have also evolved placentas. In 2001, zoologists Martha Patricia Ramírez-Pinilla and Adriana Jerez from the Industrial University of Santander in Bucaramanga, Colombia, made an astonishing discovery. They found that Mabuya lizards have remarkably advanced placentas, bearing striking similarities to our own.
While this revelation was already surprising for a reptile that typically lays leathery eggs, an even more remarkable revelation emerged 16 years later. Ramírez-Pinilla joined forces with geneticist Thierry Heidmann from Gustave Roussy in Paris, France, and his team. They uncovered that the lizards possess a gene crucial for placenta formation, and astonishingly, this gene originated from a virus.
Approximately 25 million years ago, the ancestors of these lizards were infected by a virus that integrated some of its own DNA into their genome. Instead of causing harm, the lizards somehow repurposed the viral DNA, utilizing it to develop their initial placentas. Thanks to the virus, the lizards underwent evolutionary changes and developed a new organ.
Heidmann explains, “The acquisition of genomic material coincided with the transition from non-placental to placental lizards.”
What makes this story even more intriguing is that it is not an isolated incident. Around one-tenth of the human genome is composed of viral DNA, and this viral contribution has played a vital role in our evolutionary history. Some of this viral DNA was instrumental in the formation of the mammalian placenta, while other segments are involved in our immune response to diseases and the creation of new genes. Without viruses, the process of human evolution as we know it would not have been possible.