Virus DNA in human genome (evolution by infection)

Viral Fossils in Human DNA00:00:00

Approximately 8% of the human genome consists of remnants from ancient viral infections. These 'viral fossils' are retroviral sequences that integrated into our germline cells millions of years ago, becoming permanently passed down through generations.

Domesticating Viral Genes for the Placenta00:03:05

Humans repurposed viral envelope (env) genes to create 'syncytins,' proteins that allow cells to fuse. This cell fusion is essential for forming the syncytiotrophoblast, a critical structure in the placenta that connects the fetus to the mother, facilitates nutrient exchange, and protects the embryo.

Evolutionary Impact and Convergent Evolution00:07:17

The evolution of placental mammals was driven by multiple, independent viral infections over millions of years. This process has occurred at least 10 times across different species, including non-mammals like the Mabuya lizard, demonstrating that viral gene recruitment is a recurring evolutionary strategy.