Bipedalism – characteristics of skeleton, efficiency over long distances, evidence in the fossil record, what is driving these changes?
Reproduction– Hidden estrus, permanently enlarged breasts, large penis/smaller testes, what type of mating pattern do we have? monogomish
Life History – big brains, long infancy, long childhood, reduced interbirth interval, post-reproductive phase
Big Brains – Language, Culture, Technology (especially ability to use energy from other sources), Social Intelligence
Brings “supports” (legs) in line with the center of gravity
Gluteus is composed of maximu, medius, and minimus
Action of the maximus is primarily used in squating, but the other two muscles are abductors in the modern human vs extensors in chimpanzees
Saves energy and makes bipedal locomotion more efficient.
We have large heels, ankles adapted for walking, stiff midfoot for propulsion, adducted big toe in line with others
Heel bone = calcaneus, robust and wide
Ankle (talus) in human is wide and platform-like, vs narrow, angled chimp ankle
Midfoot – Humans possess plantar fascia, which stiffens and strengthens the midfoot, also crating a noticable arch
Adducted = “added” to the midline
Abducted = “away from the midline – think “abducted”
“S” – shaped curve of the spine, same idea, brings everything in line with center of gravity for more efficient bipedal locomotion
Lower curve of back is called “Lumbar Loridosis” and does not fully appear until we begin walking.
Without this curve, the entire spine would tilt forward, requiring muscle action (and thereby energy) to maintain an upright posture.
Note the central placement of the foramen magnum (big hole for entry of the spine) in human and posterior position in chimp
Also, chimps have much more pronounced occipital protuberance for the attachment of nuchal musculature (neck muscles)
Chimp pelvis = long and narrow lliac (hip bone) blades
Human pelvis = low, broad, and rounded
This reorientation of the pelvis makes for more efficient bipedal locomotion (which is itself more efficient in long-distance travel) but creates problems…
dependent, helpless, can’t cling, can’t forage, require care
Literally “require nourishment”
Humans are “Secondarily” altricial, because it is a derived condition relative to other primates.
young are relatively mature and mobile, from the moment of birth and are able to feed themselves
Many primates are relatively precocial. They can cling at birth, nurse, move around – yes they are more dependent than other mammal babies, but compared not compared to humans
Human brains develop more than chimpanzee brains both in-utero and post natally.
Most active period of brain development is from birth to 6 years, human brain is structurally fully developed at about 8 years old, though much social, cognitive, and behavioral development continues to occur throughout adolescence.
Reproductive Senescence (Menopause)
Language is all about information retention and transfer
Facial expressions and gestures are part of the basic primate pattern, certainly part of the Hominoid pattern
Hear and see visual and vocal communication, process these sensory stimuli, organize your response, turn it into physical motions and spoken words.
Language is taking visual and gestural communication one step further (or several steps further)
How did paleoanthropology start?
Darwin and Descent of Man – thought there were lots of these ideas floating around – particularly Huxley
Linnaeus classified humans with primates
Needed the evidence – needed the fossils; with evolutionary theory we knew that humans must fit into the picture
He was ridiculed, but many of his predictions have borne out. Stated that hominins evolved in Africa, savannas, etc.
Haeckel vs. Darwin
Haeckel believed that we were most closely related to gibbons and organgutans – humans were from Asia in his opinion.
Darwin suggested Africa
But many believed that Europe would ultimately yield our ancestors
Decided that humans evolved in Asia since that was where orangs were – he was far away, people weren’t ready to accept these ideas yet.
Modern Paleoanthropology Begins in Africa in 1925
Raymond Dart- Founding father of paleoanthropology
took a post at the University of Witswatersrand, Johannesburg to head the anatomy department
Has an anatomy department with no specimens! Tells his students etc. to collect stuff – lots of fossils start to roll in
Has in the back of his mind the idea that hominins may be present (his is an academic and kept up to date on the big controversies in science of the day)
Receives a box from Taungs site.
He was dressed in a suite, headed to a wedding, and he sorts through the stuff, finds and interesting one, and immediately goes to it with his wife’s knitting needles.
Why did Dart consider Taung a hominin?
Centrally Located Foramen Magnum
BOTH proponents of a European origin…
Sts -5: Mrs. Ples (Pliesianthropus was original genus Broom used)
-Discovered in 1947, over 20 years after Dart’s Taung child
- Adult female, 450cc cranium (upper chimp range)
- Centrally placed foramen magnum, low nuchal attachments, parabolic dental arcade, less prognathic than chimps
Sts 14: Really clinched it
- morphology of spine, low, wide, broad pelvis with an articulating femur – no anatomist could claim that this thing wasn’t a biped
SK-48: Robust australopithecine form discovered just a few years after all of the sterkfontein material
One small issue – evidence for bipedalism significantly pre-dates evidence for tools.
– observed the veld (bush) around him and assumed that conditions in the past had been similar
-However, in the 1930s, with the discovery of Makapansgat, he began to argue for the “Osteodentokeratic” culture of early ape man. Depicting them as a proficient, bloodthirsty, cannibalistic hunter.
Makapansgat has produced a fair amount of material, but a lot of it was in broken bits
Worked in Omo, Koobi Fora, Lake Turkana region
Found many more specimens of Parathropus, Homo habilis, Homo erectus,
AL 288-1 discovered in 1974 at Hadar (Ethiopia) in the Afar depression by Don Johannsen
40% of skeleton of a female, appx 3.2 mya, which made her the oldest hominin fossil at the time – SA dating was questionable and probably younger
Again, clearly bipedal, bipedalism most certainly predates big brains…what is driving this evolution?
We will go more into the details of Australopithecine morphology tomorrow, but basically they show a mix of traits, somewhere between arboreality and bipedality – the perfect transitional form
Somewhat sexist and contrary to much primatological evidence
Change in life history and reproductive strategy, selection for big brain meant that the man had to “provision” the female while she cared for the offspring.
Owen Lovejoy, argues that this reduces dimorphism and selects for monogomous bonding.
Essentially an extension of the “carrying hypotheses”, bringing home the bacon so to speak
Fossil Preservation and Dating
East - Many Fragmentary Fossils
More Precise Dates
South- Mostly Complete Fossils
Less Precise Dates
Orrorin tugenensis, S. tchadensis, O. tugenensis
3.5ft tall, Curved fingers, Bipedalism, Legs longer than arms (between humans and chimps), Valgus knee, Pelvic morphology
Also: morphology points to significant adaptation to movement in trees. (And possibly sex differences in locomotion as well, with females more arboreal than males)
Afarensis becomes more robust through time (anagenesis)
Al 333: first family: 13-17 individuals, all appeared to die at the same time (flash flood?)
Mary leakey 1978
Trail is 88ft long, lincludes about 70 early human footprints in volcanic ash
Two tracks, Three individuals (a juvenile was walking in the footprints of the adult)
Possible that one individual was carrying something heavy on one side (possibly a baby?)
Heel-strike, followed by toe-off (modern walking)
3yr old (possibly female, based on known afarensis canine dimorphism)
2006: Zeresenay Alemseged
Dikika Ethiopia (near Hadar)
Most traits diagnostic of afarensis are evident at 3yrs old
Functional dichotomy of afarensis body plan:
Lower body derived for bipedalism
Upper body, ape-like
Body size similar to a chimp at age 3
Scapula resembles a gorilla (this is unexpected because the gorilla forelimbs are derived for weight-bearing during knuckle-walking)
But: cranially oriented scapula functionally related to arboreality
Hyoid bone similar to chimps and gorillas
Long curved fingers
Brain is 63-88% fully developed (chimp brains are 90% complete by 3yrs of age)
Very human like
Precision grip, long thumb, short fingers
Same body size though: Both have more dimorphism than modern chimpanzees OR modern humans
Megadontia Quotient: P. boisei: 2.7
P. robustus: 2.2
~ 2.6 Ma
Discovered in 1985 by Alan Walker in West Turkana, Kenya (EAST AFRICAN)
Called the black skull because it is manganese stained
Oldest Paranthropine with morphology that suggests possible links to Australopithecines
Face is very prognathic and actually dish-shaped, pronounced sagittal crest, large cheek teeth
Thought to be ancestral to P. boisei and P. robustus
The “Nutcracker Man”
~ 2.6 – 1.2 Ma
Found by Mary and Louis Leakey in 1959
Most “robust” of the robusts…
~ 2 – 1 Ma
Found by R. Broom in 1940s, this particular specimen is SK-48 from Swartkrans
First robustus specimen (the one that Gert Terblanche broke the teeth off of and sold to Broom) was actually found
Derived Parantrhopine Morphology For Hard-Object Feeding (?)
360 – 660 cc (~3.5 EQ)
~ 2 Ma – 1.5 Ma ?
Argued to be as old as 2.33Ma
Mandible OH-7 is the type specimen for Homo habilis (Johnny’s child, son of Mary and Louis Leakey) – we saw this specimen in the “History of Anthropology” Lecture
1960, Olduvai Gorge, Tanzania
Also includes hand and wrist bones: large thumb and broad fingertips (precision grip, stone tool making ability)
But: also has relatively long curved fingers
Also includes: parietal fragments (estimate 363cc, extrapolated to adult ~600-700cc)
Specimen on the above slide is KNM-ER 1470 shows a number of non-australopith traits like a higher forhead, less prognathism (flatter face), smaller cheekteeth
less post-orbital (behind the eyes) constriction which indicates that the frontal lobe of the brain is expanding
Fundemental bifurcation in hominin lineage
Argument has been that the paranthropines became too specialized and couldn’t adapt. To be fair, they existed for over 1mya which is 5x longer than us. Really quite successful
SJ Gould says avg. lifespan of any species is 500,000
Australopithecus – prognathic face, well-developed canines (relative to other hominins), large incisors/anterior dentition somewhat more ape-like tooth row (parallel), small cranial capacity ~400 cc, large molars
Paranthropus – less prognathic face, small canines, reduced anterior dentition, tooth row still somewhat ape-like (parallel), very large molars, molarized pre-molars, sagittal crest for temporalis muscle attachment, thick and large mandible, ~400cc cranial capacity, flared zygomatics
Homo – reduced prognathism, slightly to significantly larger brain than australopiths (500cc in H. habilis; ~900 in H. erectus), less post-orbital constriction, smaller molars, mandible is not as thick and robust as in australopiths, very parabolic toothrow
Discovered in Hadar, same locality as Lucy, lots of Au afarensis at this locality, this specimen AL-666 is the only (arguably) Homo specimen
Other H. habilis from Olduvai
Left: OH-65 (1995) 1.8Mya
Can very clearly see the parabolic toothrow, reduced dentition, and reduced canine size
Right: OH-24 “Twiggy” (1968) 1.8Mya (590cc)
Distorted, crushed flat, restoration by Ron Clarke
1470: (discovered 1972) 1.9Mya, 775cc (above the cerebral rubicon), Flat face, larger size, flat subnassally orthognathic face, anteriorly placed maxillary zygomatic roots
1470 is difficult to interpret: No mandible, no teeth, Is facial flatness a result of the reconstruction?
Is this the same species as Homo habilis (like 1813)? This would mean that Homo habilis was extremely variable
Is it a new species? We will see that Homo erectus is around at 1.8-1.9Mya in the same places. Could there be 3 different species of Homo coexisting in the same place/same time? New fossils from Koobi-Fora suggest that this is a possiblity.
We find, in both east and south africa, Paranthropines, early Homo, and stone tools all in the same deposits which strongly suggests that they co-existed on the landscape, seem to have occupied very different niches (dietary and possibly habitat?).
Earliest stone tools
Particular raw materials
Transported long distances
Stream bed cobbles
Long distances: implies greater mobility, long-term planning and foresight not recognized earlier.
Probably habitually carried artifacts and unmodified stones over the landscape.
Traditional interpretation: living floors were home bases, temporary camps, or places of activity to which mobile groups of hominins returned after foraging, prepared and ate food, and carried on family based social activities, therefore implication is that early hominins had developed a pattern of land use and sociality that was more analogous to that of contemporary hunter-gatherers than to extant non-human primates.
Man the hunter THEORY: a successful hunt put a premium on foresight, strategic planning, cooperation, communication skills, and dexteriry, all of which in turn selected for larger brains, more efficient bipedalism, and nimbler hands.
Hunting is the engine that drives a self-sustaining feedback loop of social and intellectual evolution. Early hominins lived in social groups characterized by sexual division of labor in which MAN hunted and brought back meat to his monogamous woman the gatherer at a home base, share meat, provision offspring, etc…
1.9 Mya Also!!!
The Australopith Body Plan
Homo erectus body plan
A gradistic shift
Cladistic = group all organisms that are descendant from a single ancestor into a group, no matter what the descendants look like (i.e. chimps and humans share a common ancestor and thus are grouped according to cladistics)
Gradistic = classification of groups of animals together based on overall similarity of appearance, looks for major differences in overall bauplan (despite cladistic relationship between chimps and humans, under a gradistic categorization, chimps, gorillas, and orangs are appropriately grouped for comparison due to their overall similarity
Australopiths have big guts, big chests, and little (relatively speaking) brains
Homo erectus and descendants have narrower torsos, elongated limbs, smaller guts, and significantly larger brains
This is a gradistic shift
Expansion into new niche
Religion (animism at least)
Conventional wisdom suggests that humans acquired tapeworms ~10kya with the adoption of agriculture. However an examination of mtDNA of tapeworms show that they diverged 780 kya to 1.7 mya long before the consumption of livestock.
it appears that the tapeworms of hyaenids and felids switched to a human host.
Human ultimately introduced these tapeworms to their livestock and continued the cycle of parasitism.
Modern body proportions: thermoregulation, longer distance mobility, predator defense.
Perhaps body hair loss too (thermoregulation advantages)
Vertebral canals are smaller, perhaps less efficient at speech
Gorilla lice and pubic lice are more closely related than human head lice and pubic lice
Est. split is 3.3 mya according to Reed et al. university of Florida
Loss of body hair MIGHT have been quite early…
Also split between head lice and “body lice” which live on clothes, is est. to be around 107,000 years – suggests when people began to wear tailored clothes – they probably had loose fitting furs etc, before this.
Specimens are all from a single cave locality and roughly the same time period (at the very least within a few hundred years of each other). The question then becomes whether or not H. erectus was highly variable or whether or not multiple species existed. This would suggest that multiple species of hominin left Africa! (or that they speciated once they left Africa).
Argued to be continuity with Homo sapiens from australia.
But, Pleistocene and modern Australians do not have the distinctive combo of traits seen in Javan H. erectus.
And, DNA link with another population (the Denisovans) of early humans (whether this is archaic Homo sapiens, or anatomically modern homo sapiens, we don’t know yet).
Earlier evidence at Koobi Fora and Chesowanja 1.5mya, and South Africa caves ~1mya, Swartkrans 1-1.5mya, Isreal lake margin close to 1mya, but Zhoukoudian is clear evidence.
Why are there no achulean handaxes beyond the “Movius Line”
Raw material constraints, cultural development of new tool technologies?
Out of Africa = H. erectus evolved in Africa, dispersed out of Africa; H. sapiens evolves in Africa, disperses out of Africa and then replaces existing H. erectus populations
Multi-regional Model = H. erectus evolves in Africa, disperses, and independently (in Asia, Europe, Indonesia, Africa) evolves into Homo sapiens – this doesn’t really jive with what we know about how evolution works – species that are geographically isolated generally evolve into DIFFERENT species, not the same one
At least two or three “waves” of dispersal out of Africa (H. erectus, H. sapiens) but with lots of gene flow and interbreeding between populations
Tongue sticking out is the key here…fine motor skills and tool making seem to be connected to the language centers in our brain
Transcranial Doppler Ultrasound
Areas of the brain that are activated during various elements of expressing language are also activated when tool planning, use, and creation are occuring