Question

critically evaluate the claim that Ardipithecus ramidus is a hominin. [400 words, 30 marks]

Answer 1

Ardipithecus ramidus is a species of australopithecine from the Afar region of Early Pliocene Ethiopia 4.4 million years ago (mya). A. ramidus, unlike modern hominids, has adaptations for both walking on two legs (bipedality) and life in the trees (arboreality). However, it would not have been as efficient at bipedality as humans, nor at arboreality as non-human great apes. Its discovery, along with Miocene apes, has reworked academic understanding of the chimpanzee-human last common ancestor from appearing much like modern day chimps, orangutans, and gorillas to being a creature without a modern anatomical cognate.

The exact affinities of Ardipithecus have been debated. White, in 1994, considered A. ramidus to have been more closely related to humans than chimps, though noting it to be the most ape-like fossil hominin to date. In 2001, French paleontologist Brigitte Senut and colleagues aligned it more closely to chimps but this has been refuted. In 2009, White and colleagues reaffirmed the position of Ardipithecus as more closely related to modern humans based on dental similarity, a short base of the skull, and adaptations to bipedality. In 2011, primatologist Esteban Sarmiento said that there is not enough evidence to assign Ardipithecus to Hominini (comprising both humans and chimps), but its closer affinities to humans have been reaffirmed in following years.White and colleagues consider it to have been closely related to or the ancestor of the temporally close Australopithecus anamensis, which was the ancestor to Au. africanus.Since the mid-19th century, the time of English naturalist Charles Darwin, scientists have placed all primates that are more closely related to modern humans than to chimpanzees in the zoological family Hominidae. Independent studies during the 1960s showed that humans are genetically more closely related to African apes, chimpanzees (Pan troglodytes), and gorillas (Gorilla). Since the orangutan (Pongo pygmaeus) is more distantly related, some taxonomists include the African apes in the family Hominidae, therefore demoting the ancestors of humans and their close relatives to subfamily or tribal levels of classification. This has resulted in nomenclatural instability and the widespread but confusing use of the term hominin to refer to the same set of genera and species encompassed by the more traditional term hominid. Consequently, in keeping with the need for stable definitions of scientific terms, many scientists now place within the family Hominidae the three genera that are part of the human lineage—Ardipithecus, Australopithecus, and Homo. Although many scientists also include the genera of the great apes—Pongo, Gorilla, and Pan—in Hominidae, the traditional term hominid here refers only to humans and their ancestors.