Extant Apes
Even though chimps look more similar to gorillas and orangutans, they re actually more closely related to humans according to current genetic data. The facts most scientists agree on
Brains: Chimp~320-350cc Humans ~1350cc Locomotion: Chimp knuckle walking Human habitual biped Chimp vs. Human
What evolved in the hominins first: large brains or bipedalism? Look to the fossil record!
An Early Find A nonscientist finds parts of a skull in a local gravel pit near Sussex. Only the skull was found. It is somewhat human-like, and somewhat ape-like. The missing link!!! Took the skull to scientists The skull s features
The Missing Link? Small jaw like an ape Small molars like a human Large canines like an ape Highly vaulted skull like a human (big brain!) A mix of human and nonhuman ape characteristics
Fervor over the Missing Link Yay! Proof that Europe was the cradle of humankind! Moreover, the skull s large cranial vault suggested that the European missing link was intelligent! Despite some obvious error in the analyses, the skull was celebrated for years.
Found in England ~1908-1912 at the Piltdown gravel pit Named it Piltdown Man
More fossils subsequently found (these are 2-7 myo)
Sahelanthropus tchadensis Found fossils 2001-2002 in Chad (about 100 years after Piltdown man was found)
Sahelanthropus tchadensis Features 7-6mya Found in center of Africa rather than East Africa and South Africa where most research on human evolution has been conducted Large jaw Large browridge Reduced canines Large molars Small brain~roughly the size of today s chimps at ~335cc; today s humans are ~1350cc Only skulls have been found, so we are not yet sure if Sahelanthropus was bipedal It is an unexpected mix of human and apelike features, and found in an unexpected area: this is more evidence that hominin evolution did not follow a simple progression from ape to human--rather, there were probably many different hominin species that possessed a variety of different adaptations
More fossils ~4-2mya the hominins increased in number and spread out in Africa Multiple species lived at the same time Roughly 2 categories; most found in south and east Africa Australopithecus (6 species) gracile type Paranthropus (3 species) robust type
Australopithecus southern ape Small bodies relative to humans Clearly bipedal Teeth, skull, jaw adapted to a generalized diet Small teeth relative to Paranthopus Chimp brain is ~335cc Average Australopithecine brain ~500-700cc
Australopithecis afarensis Clearly bipedal The famous Lucy
Laetoli footprints c. 3.6 MYA Footprints made in East Africa, probably by A. afarensis, several bipedal creatures walked across a bed of wet volcanic ask about 3.6mya; footprints were preserved when it dried
Australopithecus africanus Found in South and East Africa Lived 2.2-3mya Skeletons confirmed bipedality High sexual dimorphism Male canines bigger proportionately bigger than female canines (like gorillas, etc.) Males: 4 6 and 90 lbs. Females: 3 9 and 66 lbs.
Taung child (Australopithecus africanus) -2.5myo -discovered in S. Africa, 1924: the first Australopithecine fossil ever found Raymond Dart, an Australian anatomist living in S. Africa (local workers in a mining pit brought it to him) -foramen magnum location like bipedal humans, so Dart concluded it was a biped -brain small like that of an ape -rejected by scientists because at the time they believed large brains evolved before bipedalism (like Piltdown); with no postcranial skeleton, foramen evidence not strong enough to prove bipedality How did they know it was a child? It still had baby teeth and molars ready to erupt.
Gracile types: Genus Australopithecus Australopithecus africanus 2.5-2.6myo Australopithecus garhi c. 2.5myo
Robust types: Genus Paranthropus Paranthropus aethiopicus c. 2.5 MYA Paranthropus boisei c. 1.8 MYA Paranthropus robustus c. 1.5-2 MYA
Paranthropus parallel to man Similar to Australopithecines from the neck down (bipedal, short relative to humans) Small brains BUT they had massive molars and premolars, and jaws adapted to chewing tough plant materials; their skulls were modified to carry the enormous muscles necessary to power the chewing apparatus
Paranthropus Exceptionally large teeth, esp. molars (unlike Australopithecus) Exceptionally large jaws (unlike Australopithecus) Big teeth and big jaws mean: Large jaw muscle (temporalis muscle) to move the heavy, powerful jaw; jaw muscles connect up and around the sides of the head, and run underneath the cheekbones to the jaw Large jaw muscles mean: Large zygomatic arches (cheekbones) needed to create space for jaw muscle More skull for the large jaw muscles to connect to: a sagittal crest Test yourself, clench your teeth and feel your temporalis muscle--feel the muscle where it stops, about an inch above your temple Sagittal crest Black Skull (because it is black; just due to the process of fossilization with high manganese content): Paranthropus aethiopucus
Paranthropus robustus and boisei P. robustus: wear marks on molars indicate hard foods and nuts, but research on fossil contents also suggest a significant amount of meat in the diet P. boisei: a super-robust paranthropus P. robustus used to be called Australopithecus robustus and P. boisei used to be called Australopithecus boisei
To summarize 4-2mya Hominins spread around South and East Africa Small brains (~500-700cc), but somewhat bigger than today s chimps Short The GENUS Australopithecus is gracile The GENUS Paranthropus is robust Very sexually dimorphic They are clearly bipedal.
The Evolution of Bipedalism Several theories Walking on 2 legs is an efficient form of ground locomotion Erect posture allowed humans to keep cool It left the hands free to carry things Allows for efficient harvesting of fruit from low trees Different lines of evidence for and against these and other theories But one thing we know for sure: Bipedalism evolved BEFORE big brains/intelligence evolved But wait, what about Piltdown Man???
Piltdown Man: A Hoax Skull fragments were of a human--hence the large brain Jaw of an orangutan--hence the large canines Molars were filed down to look like the small molars of a human The signs were obvious, but, consistent with the prevailing notion in England at the time, people wanted to believe that large brains evolved prior to other features They also wanted to believe that Europe was the location of humans evolving from apes into modern humans A set back to science--a total waste of time Forgery wasn t discovered until 1953! Though as early as 1915 other scientists had rejected it. It did wane in acceptance with the finding of the Taung Child The hoax is still cited by creationists in support of their view that the theory of evolution cannot address the origins of man. Many cite it as evidence of the frequent acceptance in the scientific community of viewpoints with very little data.
Tools Hominins have been making stone tools for at least 2.5my A particular kind of tool found in East and South Africa dating back to 2.5 MYA: Oldowan tools
Oldowan tools
Oldowan tools -Several flakes can be chipped from I core -It is not clear if the core was used as a chopper of if the flakes were used for cutting -Experiments in knapping (stone toolmaking) have shown: -knappers were almost certainly right-handed -flakes were best at processing carcasses, though cores/choppers may have been useful in other activities Question: Who was making and using them?
Who used Oldowan tools? Probably Australopithecus and Paranthropus We don t have direct evidence of these early hominin bones associated with Oldowan tools, but that doesn t mean they didn t use them (no one died and was fossilized with an Oldowan tool in their hand, but we find the tools at the same time they were alive, and we find clearly-processed animal bones with the tools) Definitely members of the genus Homo
Homo They were the first to leave Africa, and they clearly used stone tools.
Final Group: Genus Homo (includes us) Homo ergaster (African) Homo erectus (Asian) Homo heidelbergensis Homo neanderthalensis Homo sapiens (us)
H. ergaster Several specimens have been found
H. ergaster Clearly a different genus from Australopithecus and Paranthropus Appear 1.8 mya in Africa (colder climate) Disappear 600KYA Bigger brains than earlier hominins ~800cc Probably mastered fire Probably hunted large game Used Oldowan and Acheulean tools Traits like modern humans: smaller, less prognathic face, higher skull, smaller jaws and teeth, similar body size, similar sexual dimorphism Other trait: very large brow ridges, horizontal ridge at the back of the skull (occipital torus) which allows a better biting and tearing action with the incisors and canines Biting and tearing what? MEAT. Molars are far smaller (and proportionately so) than those of the earlier hominins who were chewing and grinding hard plant foods Homo ergaster c. 1.75 mya (Africa)
Acheulean tools
Acheulean hand axes Regular, bifaced, teardrop-shaped flaked tooks; can have different sizes (few inches to 2 feet have been found) and be made of different materials, but always the same proportions; probably most used for butchering, with less use for other tasks; 1.6mya to 300kya: remarkable regularity of the tool industry for over a million years
Homo erectus 1.8mya-30kya Very similar to H. ergaster but found only in eastern Asia Large brow ridges Sagittal keel (a lump rather than a crest) with unknown function More sloped sides of skull Used Oldowan tools mostly, but a few Acheulean tools have been found in eastern Asia, and stone tools are absent from the entire region above the latitude line where bamboo grows Homo erectus c. 1.6-0.7 MYA (Asia)
Neanderthals
Neanderthals were shorter and stockier than us.
Homo Neanderthalensis Only in Europe, 137-30kya Adapted to cold environment: stalky, huge noses and faces Large front teeth, many with cut marks Well-adapted to hunting large game We clearly did NOT evolve from them; genetic evidence shows they were a separate branch that had a dead-end (I.e., they went extinct) We know a lot about them because European paleoanthropologists did a lot of digging there First one found in Germany s Neander valley LARGE BRAINS than humans, averaging 1520cc--bigger than us, who average ~1350cc (though reflects large body size, and they are about 30% larger than us) Probably buried their dead Had short, brutal lives Interesting fact: the patterns of injuries we see in Neanderthal bones match those of human?