Gibbon
Human
Chimpanzee
Gorilla
Orangutan
all have a lot in common
- much more upright posture
- big brains
- mobile ankle
diffs & similarities between human and gorilla skeletons
- gorillas chunkier / larger than humans
-> big pelvis - but v similar!
humans & apes more similar than old world monkeys & humans.
looked at Albumin, DNA & haemoglobin…
ape-human diff much smaller than old world monkey-human diff
humans are closest related to chimpanzees, only splitting ~ 5 mya.
however, if you look at skull of human, chimp, orangutan & macaque, chimp skull looks more similar to other apes than humans.
what is this eg. of?
- neoteny
- in human skull:
-> taller skull
-> less ridged brow
-> shorter face - ^what we see in fetal chimps!
hominin
- tribe that inc humans & extinct v recent ancestors
- in hominin, striking feature is bipedalism:
-> apes: quadrupedal (walk on 4 legs)
-> humans: bipedal (walk on 2 legs)
1st fossil showing bipedalism
- Lucy - found in Ethiopia
- fossil of female ape from 3.5 mya
- called Australopithecus afarensis
- adaptations in Lucy’s hip, leg & foot allowed a fully bipedal means of movement (proven by reconstruction model of Lucy)
when did bipedalism first evolve?
- at least 3.5 mya
- in Laetoli, Tanzania - impression fossil
-> evidence of australopithecines walking on 2 legs in imprints left in muddy river bank - walking on 2 legs meant hands were free to move -> this might be crucial innovation in evolution of our sp
what is selective adv of bipedalism?
walking on 2 legs meant hands were free to move -> this might be crucial innovation in evolution of our sp
knuckle-walking
- what we see in our close relatives in great apes is predominant form of locomotion is knuckle walking
- a re-evolved form of quadrapedalism -> allows animal to walk on all 4s while retaining features in shoulders & forearms to be good at climbing (chimps & gorillas)
- energetically v costly for chimps -> 75% more energy per unit mass than normal quadrupedalism
why did hominins stand up?
we don’t know…
- habitats in Africa became more open in last 3 million years (changes in climate)
- 2.6 mya - simple stone tool use & evidence of carnivory (hands free)
how did hominins hunt?
- NOT through use of projectile weapons (relatively new)
- bipedalism = not fast but economical…
- most mammals cannot sustain a gallop -> cannot pant when galloping
- humans can sustain running for hours
- humans can outrun horse over long distances especially when hot (eg. in Africa)
benefits of bipedalism
- less solar radiation -> only hits top of our head
- more upright => being hit by more air/wind so get cooling effect
- provides calories through capacity it gives us to hunt
- frees up hands
- allows brain to ↑ in size, this in turn allows for tool use, culture, language, art, smart-phones…
sweating in humans
- lack fur & have v high densities of sweat-glands all over our bodies
- this means we’re less likely to overheat
how humans are adapted to be good at running
- anatomy = great for running
- long legs, large gluteus maximus, long tendons
- springy, bounding gait
adaptations to be good at running gives human ancestors the abiity to be good at hunting, giving us v high energy food resource
- reward to cost is high -> cost of running only 40% more than walking
- 15km chase only requires 1100 kcal (doesn’t require lots of meat)
- when ppl study San Bushmen in Kalahari, their success rates in these hunts is v high (~50% success rate of persistant hunting)
race is an old concept
- Homer - refers to Ethiopians; literally ‘burnt face’
- skin colour referred to less often than religion, language & geographical origins
Carl Linnaeus 1707-1778
invented binomial naming system for organisms in Systemae Naturae
Linnaeus’ human taxonomy:
- Europeanus: white; blue eyes; gentle, acute, inventive; governed by laws
- Americanus: red; black, straight, thick hair; stubborn, zealous; regulated by customs
- Asiaticus: yellow; stiff; black hair, dark eyes; haughty, greedy; ruled by opinions
- Africanus: black; frizzled hair; silky skin, flat nose; females without shame; crafty, lazy; governed by caprice
humans originated in Africa
lot more genetic diversity in Africa than rest of world
Multilocus analysis of race - 53 populations
- looked at 360 loci in genome
- looked at ~1056 individs from 53 diff pops
- ^gives rough idea of how much variation there is across the genome
- then divide genetic variation into 5 groups -> these groups map onto geographic areas
- shows lots of evidence of genetic mixture between pops BUT is geographical signature in pops of humans
MAIN BITS:
- within-pop differences account for ~94% of genetic variation
- 6 main genetic clusters, 5 of which correspond to major geographic regions
- differences among major groups constitute only 3 to 5%
2020: Genomic analysis of race - 54 populations
- sequenced 929 genomes
- each pops harbour unique variants, but none is fixed between regions
- substantial gene flow between populations
traits under strong selection can vary between human population
- Tibetan Sherpas
-> evidence of selection on genes associated with metabolism (to deal with high altitude)
-> Andean pops too - Greenland inuit
-> adaptations to high fat diet (seafood diet)
BUT
- observations of genetic diffs are limited to specific adaptations to extreme env
- no evidence for diffs among ethnic groups in general-purpose adaptations eg. athleticism or IQ
race and biology
- alleles associated with both light & dark pigmentation predate Homo sapiens by 100,000s of years
- more variation in pigmentation within Africa than in rest of world
- most genetic variation occurs within pops
race is a social construct
- racial groups are “constructed” from historical, political, & economic contexts
- racial groups do not correspond well to inherited, biological variations
eugenics
= good breeding
“study of the agencies under social control, that improve / impair racial qualities of future gens either physically or mentally”
-Francis Galton
