After working like mad to finish my thesis I can finally get back to my theology and evolution blogs. In this installment we take a look at a very important branch of the evolutionary tree – ours! Allow me to introduce you to some of our hominid and hominin forefathers (and mothers). Hominid used to refer to the family Hominidae, as distinct from the family Pongidae (chimpanzees), but the term now refers to Hominidae as it stands now, including chimpanzees and bonobos in the family. Hominin is the term employed for the lineage that has already diverged from that of the chimpanzees and which leads up to modern humans.
Anti-evolutionists often ask to be shown the fossils. Richard Dawkins recounts a rather infuriating interview (pgs 198-201) which would let any sensible person want to bang their head on their desk.
- Sahelanthropus tchadensis is the earliest known bipedal ape. Discovered in 2002 in Chad, this creature lived about 7 to 6 million years ago, which is 1 to 2 million years before the lineages of humans and chimpanzees split according to DNA studies.
- Orrorin tugenensis was discovered in 2000 in Kenya, walked upright, and lived about 6 million years ago.
- Ardipithecus ramidus (basic root ape) seems to be the point where the human lineage began. It was discovered in 1994 in Ethiopia and clocks in at about 4.4 million years ago.
- Australopithecines (literally “southern ape”) were hominins that lived in Africa. They were bipedal, but their brains were not consistently larger than other apes. Their leg and pelvic bones attest to upright walking, but a bony ridge on the forearm, which might be vestigial, points to walking on the knuckles.They probably used tools, but much in the same way chimpanzees do today. The earliest species were A. anamensis, A. afarensis, and A. bahrelghazali from about 4 to 3 million years ago. A. garhi and A. africanus lived in the southern regions of Africa at about 3 to 2 million years ago. The Australopithecines are described as “gracile” and were small of stature, only measuring about 1m tall.Their jaws were relatively small as were their faces.
- Australopithecus afarensis was discovered in 1974. The fossils date from 3.9 to 3.9 million years ago and had humanlike teeth (Isaak, 2007: 106). The first specimen discovered is also the most famous. The nearly complete skeleton of Lucy was helpful in shedding light on the movements of the species. A. afarensis was bipedal. Fossilized footprints of A. afarensis or a closely related species that evidence bipedalism were found in Tanzania in volcanic dust which was dated to about 3 million years ago. The “Dikika Baby” was found in 2006 in Ethiopia and from the shoulder blades it could be deduced that the species could still swing from trees. “Little Foot” was discovered in 2006 in South Africa at Sterkfontein. There are bones from about 150 individuals.
- Australopithecus africanus was discovered in 1924 in a Pleistocene limestone quarry in the Transvaal region near Taung, South Africa. The most famous specimen is the first, called the Taung child. A. africanus have humanlike teeth. This species shows that the skull’s characteristics became more modern before the brain size increased as well as that human evolution began in Africa. The specimens date from about 3 to 2 million years ago and have a brain capacity of 420-500 cc.
- Kenyanthropus platyops was discovered in Kenya and is thought by some to be the ancestor of humans, rather than Australopithecus. Kenyanthropus lived about 3.5 million years ago.
- Paranthropus is a genus consisting of three known species called the “robust australopithecines.”
- Paranthropus aethiopicus was probably the ancestor of both P. robustus and P. bosei. The Paranthropus lineage seems to have met a dead end. The “robust australopithecines” were most likely the descendants of the “gracile australopithecines,” after the line split into at least two branches. The other branch would lead to the Homo species.
In the next installment we’ll look at our Homo predecessors.
Cotner, S & Moore, R 2011. Arguing for evolution: An encyclopedia for understanding science. Greenwood: Santa Barbara.
Rice, S A 2007. Encyclopedia of evolution. New York: Facts on File.
Ruse, M 2006. Darwinism and its discontents. New York: Cambridge University Press.