#austrolopithecine

Humans and Monkeys (Part 2 of 3): Hominoids and Hominins

Hominoids evolved from Old World Monkeys 25 million years ago. They can be categorised by an enlarged braincase, lack of tail and retention of grasping toes. This group contains apes seen today including the chimpanzee, bonobos, orang-utans and gorillas. The group can be split into the lesser apes (known as Hylobatidae) which includes gibbons and the Hominidae (Orangutans, Gorillas and Chimpanzees). Hylobatidae are arboreal (live in trees) and bipedal (walk on two legs).

Hominins however diverged from the Pan genus (chimpanzees) 6 million years ago. Despite all the photos seen on the internet showing human evolution, this was not a linear process. Hominins developed over a long time through many species, with some lines going extinct and other times when several species existed simultaneously. Despite this fact due to the nature of the fossil record we only know about some of these species in detail. The first hominin we know about in detail is Ardipithecus.

Ardipithecus lived between 6 and 4.4 million years ago in Ethiopia, was around 1.2m tall, and weighed 50Kg. Ardipithecus still had a chimp-sized brain and blunt teeth (thus was an omnivore). Most importantly however Ardipithecus kept its grasping big toes, meaning it was likely to have still been arboreal, however, this was the first hominin capable of bipedalism seen through its pelvic structure.

Australopithecine is known as the Southern Ape; there were at least four species of this Ape that lived from South Africa to Ethiopia between 4 and 2 million years ago. Most Australopithecines were between 1 and 1.5m tall, however, sexual dimorphism (the difference between a female and male of a species) was shown with males being up to 1.5x the mass of females. Like Ardipithecus, Australopithecine had long arms and fingers, meaning it too was adapted to tree climbing. However, it also had feet and short legs which were suited to bipedal movement on the grasslands. Bipedal movement was beneficial as it gave australopithecine a height advantage for spotting predators and they could use their arms while moving.

There are two famed ‘types’ of Australopithecine, gracile and robust. The most famous skeletal example of Gracile Australopithecines is Lucy, a 40% skeleton of a female Australopithecus found in Ethiopia. Like other gracile Australopithecines, Lucy was a lightly built omnivore and was bipedal. We know Australopithecine were bipedal as Laetoli, Tanzania shows 2 sets of australopithecine footprints walking side by side, dated to 3.7 million years old.

Robust Australopithecines are also known as Paranthropus (meaning beside human). They were around between 2.7 and 1.2 million years ago. Paranthropus was particularly noticeable due to its strong sexual dimorphism, skull crest, large jaws and teeth. Finally, the last link we know about in detail between Australopithecus and the genus Homo is known as Habilis (or handyman), yet scientists are still debating whether this group were Australopithecus or a Homo. The first specimen of Habilis was found in Tanzania by the Leakey family. Habilis lived between 2.3 and 1.4 million years ago, is thought to have had some basic vocalisation, and began to use some stone and bone tools. Next up, the Homo Genus.

~SA