Episode 5: The placenta as we've never seen it: built from ancient viral DNA?
Did you know that a significant part of what makes us mammalian is actually viral?
In 2006, scientists discovered that over 8% of our genome is from retroviruses — yes, viral DNA that’s been lying inside us for millions of years.
Most of this genetic material is just 'molecular sediment', but some parts are still actively shaping our biology — like the placenta. That fusion of cells, critical for nourishing and protecting the fetus, was made possible by viral genes that integrated into our ancestors' DNA.
The most astonishing part? Viral proteins not only helped evolve complex organs like the placenta but are still at work today, likely influencing early embryonic development and immune tolerance.
This means our modern physiology is partly a viral legacy — an ongoing negotiation between ancient infection and survival. What other parts of your body might still be 'built from' viral remnants?
Worth pondering.
