The unprecedented pace of scientific progress on Covid-19 builds on groundbreaking discoveries from the past.
Traditional microscopes make it look like sperm tails undulate symmetrically -- but that's an optical illusion.
Researchers found a "ghost population" that interbred with the ancestors of modern humans.
Nearly complete skull of Australopithecus anamensis found in Ethiopia.
Mixtures of chemical pollutants may harm people and wildlife, even when each chemical is below its regulatory threshold.
A study that compares the multitasking abilities of awake sleepwalkers and non-sleepwalkers provides insights into the nature of awareness.