Final answer:
Among numerous fossil hominoids, only a select few, such as Samburupithecus and Ouranopithecus, show clear shared specializations with today's great apes. These fossils support the notion that all modern apes and humans share a common ancestor, dating back to approximately six million years ago.
Step-by-step explanation:
When we delve into the subject of human evolution, we encounter various fossil hominoids, which are potential ancestors to the great apes alive today. However, the critical challenge in paleoanthropology is finding fossils with clear shared specializations with living great apes. Of the numerous fossils discovered, only a few, such as Samburupithecus and Ouranopithecus, provide this connection to the modern African apes. Samburupithecus, specifically, has molar teeth elongated from front to back, akin to modern African apes, while Ouranopithecus shares facial morphology with both African apes and humans.
The term 'hominin' refers to species that evolved after the primate line divided, putting them closer to humans than to chimpanzees, including our own species, such as Australopithecus and Homo erectus, and non-ancestral groups that are 'cousins' of modern humans, such as Neanderthals and Denisovans. The fossil record and DNA comparisons suggest that humans and chimpanzees share a common ancestor from approximately six million years ago.
Noteworthy Miocene epoch apes like Proconsul and Sivapithecus also contribute to our understanding of ape evolution, indicating the diversification and specialized traits developed over millions of years. It is from this complex tapestry of fossil evidence that we deduce the evolutionary lineage of modern apes and humans, though definitive links are rare and pursued with rigorous scientific scrutiny.