Bioanth unbc midterm 2

What used to be thought to be the hallmark of being a human?

A big brain. This was a Eurocentric bias. back in the 1960s or so

What discovery was made in 1970's?

Bipedalism

Facultative Bipedalism?

adoption under particular circumstances as an exception to habitual form of locomotion. (they can but they're not built for it)

Obligate bipedalism?

A condition of necessity. you are obligate biped. only bipedal when standing on both legs.

Why don't we fall over when we walk/run?

Our pelvis is short top to bottom and wide side to side. This change re-orients the direction of the three gluteal muscles. gluteus maximus, Medius, minimus.

Differences between our pelvis and ape pelvis and glutes

ape glutes are behind the pelvis and all act as extensors (pull back) in humans the meus and minimus re on the side as extensors, rotators, and (esp.) abductors. they pull back but also outward when standing on one leg in the stance leg.

What do abductors do?

the abductors pull on the weighted leg to keep you balanced

What changes did bipedal locomotion produce in anatomy?

Changes throughout the entire skeleton. An orthograde (vertical) trunk, weight transfer, balance, and mechanical efficiency.

Foreman magnum

Large hole for exit of spinal column. Anterior in humans instead of posterior as it is in apes.

S curved spine, lumbar and cervical

Our spines are s shaped instead of C shaped. the cervical curve comes from achieving head balance as babies and the lumbar curve comes from infants learning to walk.

Valgus Knees

we have inwardly displaced orientation of knees. shanges the shape of upper and lower portions of the femur

Bipedal foot

A non opposable big toe, longitudinal and transverse arches, longer hind and mid-foot structure, for balance efficiency and power.

benefits of bipedalism

Surveillance, carrying, thermoregulation (less solar radiation and more wind to cool down), energetic efficiency

What running is unique to humans?

Endurance running and using aerobic metabolism. there are up to 32 anatomical skeletal features that relate to long distance running contributing to body stabalization, thermoregulation and stride length. large G maxiums is the major leg extensor employed in running.

Downsides of bipedal locomotion?

High BP, Fallen arches, lower back pain, knee problems, inguinal hernias, childbirth

How are human infants born in terms of development compared to apes?

Human infants born at a less-developed stage of brain development compared to other apes

What do brain size and pelvis shape force in human birth?

Brain size and pelvis shape requires rotational birth in humans

What is the OD hypothesis?

•Trade-off between brain growth and pelvic shape leads to altricial infants (infants who are born helpless) (OD)

What is the EGG hypothesis

•Birth timing and developmental stage reflects maternal ability to provide energy to fetus versus offspring (EGG)

Obstrictic dilemma

based on functional mechanics of birth. Small birth canal + larger heads = earlier birth via rotation

Rotational birth

Inlet is wide from side to side but by midplane the greater width shifts to anterior-posterior at outlet. Mother contracts in birth cause the infant body to rotate 90 degrees

When did the birth adaptations begin?

3.4 and 1.0 million years so, modern humans have created width front to back. likely in the last 1.5 m years pelvis shape changed

Is rotational birth really unique to humans?

No there are 3 cases of rotaitonal birth recorded in chimpanzees. With the baby just falling unguided onto the ground

What happens in humans vs chimpanzees during birth

The center of mass moves forward in humans and in chimps in moves downwards. in humans this creates an imbalance. it is corrected by curvature of the lower human female spine. Termed lordosis = more pronounced lumbar curve

What condition was present in our ancestors (lordosis in ancestors)

Conditions is Australopithecus africanus. 2.6 mya. not in a deemed male specimen dated to 2.1 mya

Teeth of old world monkey

2 incisors, 1 canine, 2 premolars, and 3 molars in each quadrant.

What two distinctive differences between hominin dentition and that of apes?

1. reduction in canine size and loss of honing mechanism in hominins (sharpening, relates to social organization)

2. Increasing molar enamel thickness

Enamel in teeth - thickness, role in indicating taxonomy

thickness varies among hominins over time, generally considered a weak indicator of taxonomy, more likely related to diet (early hominins) and lifespan (us)

Brain size during growth

In hominins and especially humans, most brain size growth is postnatal. The obstetric dilemma and the energetics of growth and gestation ideas.

Brain size during evolution

Among hominins there is a rapid change in brain size ca 2 mya with the appearance of Homo erectus

How do brains divide their energy

15% of cardiac output, 20% BMR 25% glucose use. costs even more for subadults

Behavioral development

•Shift in food getting = dedicated cooperative hunting versus opportunistic hunting and scavenging

Anatomical development

increasing body size, especially leg length, increases stride length and lowers cost of transportation, again with appearance of H. erectus

Physiological development

Expensive tissue hypothesis

Expensive tissue hypothesis

Essential organs have energy costs, to feed larger brains meant starving other organs, in our case the gut was simplified. This would be supported by the change in diet as noted. But some data suggests not the case for mammals in general including primates.

Alternative to expensive tissue hypothesis?

Energy input (more efficient hunting and food sharing) and energy use (modulating growth of body to support growth of brains)

Australopithecines

known in east and southern Africa - several hundred fossil remains. 4.2 to 1.1 ma. The first obligate bipeds. the first evidence of increasing relative brain size = encephalization. significant dental reduction (exception: megadont forms) considerable variation including sexual dimorphism

Gracile

Australopithecus afarensis (and others) (east Africa) Au. Africanus, Au. Sediba (south Africa) more a slight

relatively large non-projecting canines. dished faces. small, non-bicuspid premolars. high sexual dimorphism.

Robust

Paranthropus boisei (and others) (east)

P. robustus (south)

Postcanine megadontia. molarized premolars. sagittal crest. wide faces, flared cheekbones, support large chewing muscles for a hard diet.

2 sites in south africa

Steinfontein and Malapa

Sterfontein

200 limestone caves in tottal. 13 fossil localities. both gracile and robust forms; also early members of the genus homo.

Malapa

2 Ma. several cave deposits. At least 3 partial skeletons. sediba.

East africa sites variable

More open (less trees); predation is still likely a major COD. ‘Wetter’ further south

What does mosaic evolution refer to

the retention of ancestral features in a descendant form. It reflects features evolving at different rates.

Grade

Is used to refer to forms that share features in common but not necessary due to an ancestor – descendent relationship

E.g., living apes constitute a ‘Grade’ of primate distinguished from the Grade of monkeys

Clade

At the most simple level, is used to refer specifically to forms in which we infer an ancestor – descendent evolutionary lineage

E.g., all the members of the genus Homo going back ca. 2.5 million years form a clade

Proto-Hominins: Sahelanthropus

Chad, North Africa, 6 – 7 Ma, Swampy, wooded environment (fauna), A hominin???, Flatter face, Worn canine teeth, Forward placed foramen magnum, Not universally accepted

Australopithecines

Widely known East and Southern Africa - several hundred fossil remains, 4.2 to 1.1 Ma, Two body types in both East and South Africa:

•Gracile

•Robust

The first obligate bipeds, First evidence of increasing relative brain size = encephalization, Significant dental reduction, Exception: megadont forms, Considerable variation, including sexual dimorphism

South African sites

South African sites primarily cave deposits

•remains likely carnivore kills, Sterkfontein

•> 200 limestone caves in total

•Ca. 13 fossil localities

•Both gracile and robust forms; also early members of the genus Homo

•2.6 to 1.1 million years ago (Ma), Malapa

•Ca. 2 Ma

•Several cave deposits

•At least 3 partial skeletons

•Au. sediba

East Africa

East African sites variable, more open (less trees); predation still likely a major COD, ‘wetter’ further south, Hadar (further north) drier than Malawi…/

mosaic evolution

refers to retention of ancestral features in a descendant form

week 8

Atapuerca- spain

A world heritage site, series of caves documenting human occupation from 1.2 Ma to Neolithic. the most significant sites are Gran dolina. 850, 000 to 780, 000 BCE, several hominins (adults and children) cutmarks suggest cannibalism, homo antecessor. Sima de los Huesos (pit of bones) 350, 000 - 530, 000, several thousand hominin bones/fragments from at least 28 individuals. mtDNA sequenced from 400, 000 BCE femur linked to denisovans. taxinomically linked to homo heidlebergenisis

The rising star Cave

located in the cradle of humankind in S. Africa. Two main chambers (dinaldi and lesedi) dating 200, 000 - 300, 000 BCE. At least 15 individuals from dinaldi and at least 3 from lesedi, males and females old and young. attributed to homo-naledi

the rising star cave bones and dif skeletal things

pros

appear to have been intact when deposited and located in highly inaccessible locations in the caves. no trauma (ie likely not dropped into the chamber) no evidence of chamber having been flooded and bodies washed in. but would have required light source and deposits suggest not all brought in at same time.

cons

preservation due to natural mummification rather than burial. some long bones lack epiphyses (heads), suggestive of predation. Does burial suggest the concept of an afterlife - too early for this kind of symbolic behavior? but could also be for sanitation or to avoid attracting scavengers

Densiovans

very few remain linked to these archaic hominins. date to late lower and middle paleolithic (300, 000 to 75000 years ago) Dental remains and a partial mandible and long bones recovered fro mthree localities. first discovered 2008 in deisova cave in south central Siberia. some populations adapted to high altitude and low oxygen. first time a new taxon identified by DNA analysis. DNA recovered from the first fossil found, the base of the third phalange and later a molar tooth. shared DNA with both Neandertals and modern humans but shared more with the former.

Densiovan interbreeding

•Estimated that some modern humans share 5-6% of DNA with Denisovans (but only 2% with Neandertals)

•Suggests more recent interbreeding with Denisovans?

•Greatest amount of DNA shared with Melanesians, least with Europeans

•Presence of both Denisovan and Neandertal DNA low on the X chromosome and for genes acting on testes; suggesting selection to remove such archaic DNA through male infertility

what does thal in neadterthal mean

valley (named after discovery in neader thal) in 1901 german orthographic revision changed thal to tal

Engis, belgium site

1829 - 1830, 1 child, ca 4.0 years old, child associated with extinct fossil animals ca 70, 000 BCE. Labelled neandertal 1963

Forbes quarry gibraltar site

older adult female cranium deemed ancient human, Ca. 50, 000 BCE, status as neandertal 1865

what did Leine fodlhofer grotte find in neander thal in 1856?

skull cap and 14 bones, cave destroyed by limestone mining in 19th century, at least 3 individuals, artifacts and fauna

when were neandertales generally considered to be?

230 - 28 kya. las known from southern iberian peninsula - refugia

Where were neandertals generally considered to be? what is the range based on?

circum - mediterranean (except N. AFrica), southern england, east to russia and western siberia. range based on both morphology and genetic data

how many sites in western europe, iberia, itally, balkans, central and eastern europe, middle-east, and in central asia. what is this based on?

•24 sites in western Europe, 12 in Iberia, 3 Italy, 2 in Balkans, 9 central and eastern Europe, 11 in Middle-East, at least 4 in central Asia

•Based on skeletal or cultural material (Mousterian)

Chagyrskaya cave

59 - 51 kya. 11 individuals : 6 M 5 F, children and adults. short term hunting camp (horse and bison remains plentiful)