If we were to weigh all the bacteria on Earth, their mass would be about 1,000 times more than all humans. If all of the viruses on the planet were laid end to end, they would stretch for 100 million light years.
About eight percent of the human genome's DNA comes from retroviral infections we've endured over our evolution. From them, we've inherited memory and the ability to give birth to live young.
Our gut microbiota communicates with our brains and can directly affect our mood and influence our behavior.
We modern humans have our ancestors' romantic soirees with Neanderthals to thank for genetic defenses against countless viral diseases.
How the transition from hunting and gathering to agriculture was a double-edged sword that brought us innovative progress and population-decimating pandemics.