Final answer:
The Orrorin tugenensis fossil is significant due to its age and anatomical features that suggest it was bipedal and possibly a direct ancestor of modern humans, challenging the place of Australopithecines in our evolutionary history.
Step-by-step explanation:
The significance of the Orrorin tugenensis fossil is rooted in its age and unique anatomical features, which suggest early bipedalism and position this species as a possible hominin. Found in Kenya in 2001, Orrorin is approximately 6 million years old (MYA), predating other known hominins such as Australopithecus. Key features that point to bipedality include a larger femoral head and square molars with thick dental enamel, akin to those of modern humans. The discovery of Orrorin provides important insights into early human evolution, potentially making it an ancestor of modern humans and challenging the role of Australopithecines in the human lineage. As research continues, the fossil record of Orrorin and additional specimens may offer further clarification of its significance in our evolutionary history.