Bigfoot and the Yeti are often characterized like the Loch Ness Monster and unicorns as mythical creatures. But there is the possibility that another primate species exists who shares part of our evolutionary heritage and walks on two feet. Most likely, such animals would be large, hairy, and not very friendly to humans. Sasquatch faces lots of skepticism, and the evidence supporting its existence is often disputed. But there are legitimate scientists who believe in these creatures and are trying to convince the scientific community to take them seriously.

AAAS Member Jeff Meldrum, professor of anatomy and anthropology at Idaho State University at Pocatello, specializes in primate bipedalism. He has spent his life researching the evolution of human movement on two feet, and has long been fascinated by the possibility that we have an evolutionary relative who shares this trait.

Several years ago, he found fresh Sasquatch tracks in the Blue Mountains of the northwestern United States, and his passion for the science behind these creatures grew. In his book, Sasquatch: Legend Meets Science, he looks at the science behind Sasquatch and gathers scientific evidence to support the existence of this possible human evolutionary relative. In this podcast, he reads a section of his book recounting his discovery of several Sasquatch tracks and his initial skepticism about their validity.

• Check out Meldrum's book Sasquatch: Legend Meets Science

The 2.8 million-year-old mandible and teeth push back the origin of the human genus by nearly half a million years.

Researchers have revealed new details about the brain, pelvis, hands, and feet of Australopithecus sediba, a primitive hominin that existed around the same time early Homo species first began to appear on Earth. The new Au. sediba findings, unearthed in Malapa, South Africa, make it clear that this ancient relative displayed both primitive characteristics as well as more modern, human-like traits.

Due to the “mosaic” nature of the hominin’s features, researchers are now suggesting that Au. sediba is the best candidate for an ancestor to the Homo genus.

Two partial skeletons unearthed from a cave in South Africa belong to a previously unclassified species of hominid that is shedding new light on the evolution of our own species, Homo sapiens, researchers say. The newly documented species, called Australopithecus sediba, was an upright walker that shared many physical traits with the earliest known Homo species—and its introduction into the fossil record might answer some key questions about what it means to be human.