Google is celebrating the 100th birthday of famous archaeologist and anthropologist Mary Leakey in the usual way, with a doodle. The doodle shows her next to one of her greatest discoveries, a set of hominid footprints some 3.6 million years old.
The footprints, discovered in 1978, are the oldest to show bipedal hominids and proved that there were bipedal species that far back.
The discovery helped settle a heated debate over whether early humans first developed a big brain and then started walking upright, or the other way around.
The footprints, though millions of years old, are almost identical to the footprints of modern humans, and indicated that these early hominids walked very much like modern humans well ahead of any big-brained hominid to develop.
Though the footprints are one of Leakey's biggest discoveries, it's hardly the only one. She found the first Proconsul skull, an early now extinct ape, and also the important Zinjanthropus skull, known as the Nutcracker Man.