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Eco and Evo > Hominidae Evolution > Flashcards

Hominidae Evolution Flashcards

1
Q

hominidae

A

includes orangutans, gorillas, humans, bonobos, and chimpanzees

great apes/hominids

large body size

long arms, short legs, no tail

sexual dimorphism
-degree varies, typically males larger than females

omnivorous, most have preference fore fruit

large brains for body size

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2
Q

evolution of human lineage

A

estimates of chimpanzee and human MRCA range ~7 to 8 may

humans did not evolve from chimps, but rather from this common ancestor

lots of intermediate taxa that are now extinct

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3
Q

3 extinct genera

A

Ardipithecus (5-4 mya)

Australopithecus (4-2 mya)

Paranthropus (3-1 mya)

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4
Q

1 extant genus

A

homo (3 mya-present)

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5
Q

Ardipithecus (genus)

A

two extinct species that lived 4 to 5 mya
-fossils from Ethiopia

Grasping hallux (big toe)
-adaptation for locomotion in trees

but hands more like modern humans than chimpanzees,
and pelvis also appears well suited for walking upright

brain slightly smaller than modern chimpanzee

reduced canines
-social structure with less aggression?
-chimpanzee males have relatively large canines and
high aggression between social groups

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6
Q

Australopithecus (genus)

A

7 to 9 extinct species that lived about 4 to 2 mya

fossils from eastern Africa

brain sizes ~35% the size of humans

high degree of sexual dimorphism (larger males)

teeth wear suggest mainly fruit diet, but also
vegetables and tubers
-fossil evidence of butchered animals near Australoptihecus
fossils also suggest meat consumption

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7
Q

Australopithecus afarensis

A

oldest member of genus; lived 3-4 mya
-“Lucy” fossil from Ethiopia

“Gracile” (slender) body type

about 3.5 to 5 feet tall

strong evidence of bipedialism

  • shape of pelvis
  • angle of femur
  • attachment of muscles around knee

arboreal or terrestrial?

  • curvature of fingers/toes adapted for grasping (arboreal)
  • loss of grasping hallux (terrestrial)
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8
Q

Paranthropus robustus

A

lived 1.5 to 2 mya

“robust” body type

  • strong upper body
  • large skull with flare face and no forehead
  • large brow ridges
  • large herbivorous grinding teeth in mandible

most specimens have sagittal crest
-indicates strong jaw muscles

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9
Q

sagittal crest

A

indicates strong jaw muscles

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10
Q

1 extant genus: homo

A

7 or more species
-1 extant species = homo sapiens

genus is about 2.5-3 mya old

generally characterized by:

  • long lower legs (walking and running)
  • smaller teeth
  • larger brains

bulge of Broca’s area (essential for speech) becomes visible

evidence of tool, fire, and burial of dead

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11
Q

Broca’s area

A

essential for speech

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12
Q

adaptation for bipedalism

A

foramen magnum more anterior

trunk

  • S-curve of spine
  • larger surfaces for muscles supporting upright posture
  • expanded lumbar area

shortened forearms

pelvis and legs

  • narrow pelvis
  • femur angled toward midline
  • long legs

feet

  • all toes point forward
  • enlarged heal and arch
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13
Q

bipedalism

A

bipedalism frees hands for carrying items, tool use

may be particularly beneficial in open habitats
-travel greater distances for food

overall trend of cooling temperatures in past 10 my

  • partly dye to continental drift and changing ocean currents
  • expansion of grasslands (particularly in Africa)
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14
Q

evolution of big brains

A

positive feedback between cultural/linguistic complexity technological advances, and diet

benefits

  • store information
  • quickly process information
  • problem solving
  • abstract ideas

costs

  • lots of energy- your brain is 2% of body size but uses 20% of your energy
  • more difficult childbirth

larger brain evolution may be linked to increased meat intake (energy)

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15
Q

biogeography history of Homo

A

oldest Homo species were in Africa

some species migrated out of Africa before the first H. sapiens

most notably:

  • H. erectus in Asia
  • H. neanderthalensis in Europe

so before Homo sapiens, there were homo species in Africa and Europe

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16
Q

fossil evidence of where homo sapiens originated

A

oldest H. sapiens fossils are all from Africa
-up to 195 mya

first H. sapiens fossils in other continents are 30-60,000 years old

17
Q

molecular evidence of where homo sapiens originated

A

greatest extant genetic diversity in African population
-san people of souther southern Africa

populations outside of Africa have less diversity, consistent with:

  • younger populations
  • bottleneck during founder event

also evidence for introgression with other Homo species

18
Q

evolution in modern Homo sapiens

A

whole genome data from >3000 UK citizens

examined genetic variation and tested for signatures of recent natural selection

higher points = detection of selection
LCT: lactase gene
MCH: major histocompatibility complex (immune system)

19
Q

Lactose intolerance

A

most mammals only drink milk early in development while nursing

enzyme lactase is produced to break down lactose (sugar) in milk

lactase expression is reduced after weaning
-costly to produce when not needed (not drinking milk)

20
Q

Lactase persistance

A

in Europe, humans started raising livestock 8-9000 years ago

  • availability of milk for increased nutrition (advantageous)
  • human niche construction

alleles that keep lactase general turned on past weaning were selected for because they provide higher fitness

evolution of lactase persistence

21
Q

selection in UK population

A 
Other traits under selection:
– Pigmentation (-)
– Height (+)
– Infant head circumference (+)
– Female hip size (+)
– Fasting insulin (+)
– Glycated hemoglobin (+)
– … and others
22
Q

UV radiation

A 
UVB:
– Damages skin surface, causes
sunburns and some skin
cancers
– But also causes synthesis of
vitamin D
– Vitamin D needed for absorption
of calcium
UVA:
– Less intense than UVB, but
causes skin damage
– Breaks down folate
– Deficiency of folate can lead to
birth defects and decreased
sperm production
23
Q

distribution of UV radiation

A

near equator: high levels of UV radiation
-both types

also less seasonality
-changes during years

24
Q

skin pigmentation

A

human ancestors Africa
-moved from forest to open, hot habitats

selection for cooling mechanisms
-more sweat glands and less hair

more skin exposure = selection for more melanin

  • melanin protect form UVA, breakdown of folate
  • since UVB levels are so high, vitamin D synthesis persists

migration to Europe = lower UV radiation

alleles that resulted in less pigmentation have higher fitness
-increased ability to make essential vitamin D

hypothesis that skin pigmentation is a balance between the pros (vitamin D production) and cons (folate breakdown) of UV radiation

25
Q

primates

A

consists of two main groups: prosimians and anthropoids

26
Q

prosimians

A

“before-monkey”

most living today are relatively small in size, reside in trees, and are active at night

includes lemurs, lorises, pottos, tarsiers

27
Q

anthropoids

A

“human-like”

includes New World monkeys, Old World monkeys, gibbons, hominidae or great apes

28
Q

hominins

A

a monophyletic group comprising the Homo sapiens and more than 20 extinct, bipedal relatives

29
Q

braincase

A

the portion of the cranium that encloses the brain

it does not include the facial bones

30
Q

Cro-Magnins

A

a population of Homo sapiens who were accomplished painters and sculptors and who buried their dead in carefully prepared graves

31
Q

Neanderthals

A

another recent Homo species

made art and buried their dead in a ceremonial fashion

32
Q

out-of-Africa hypothesis

A

the reading hypothesis for the evolution of Homo sapiens

contents that Homo sapiens evolved its distinctive traits in Africa and then dispersed throughout the world

it claims that Homo sapiens evolved independently of the earlier European and Asian species of Homo–meaning that there was no interbreeding between Homo sapiens and Neanderthals, Homo erectus, or Homo floresiensis

Eco and Evo (15 decks)

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