chapter 55 Flashcards
what causes increased complexity in an organism?
- differences in gene expression
- changed in space (tissue) and time (developmental stage)
genetic toolkit
idea that same genes are used in different ways, leading to distinct morphological differences
impact of ‘genetic toolkit’ gene expression in humans
- humans have 39 hox genes organized into 4 clusters
- mutations can be lethal
eg
Hox A1 (homozygous) = severe mental development delay
HoxA13 = development of fingers and toes
mesozoic era
age of reptiles, after precambrian supereon
triassic
jurassic
- reptiles
- angiosperm
cretaceous
- mammals, first placental mammals
angiosperm
- flowering plants
- most have endosperm within seeds (nutritional)
- most make fruit with seeds
- most diverse group of land plants
cenozoic era
age of mammals
- extinction of dinosaurs created ecological opportunities for mammals
- mammal success probably linked to diversification of angiosperm
- Homo sapiens appear
what’s so special about seeds?
they’re a synapomorphy!
- before seeds, plants used spores
- spores have little stored food resources
relationship/impact between angiosperms and animals
reciprocal relationship
- angiosperms evolved to depend on animals for pollination, defence and dispersal
- reward with nectar, fruit and shelter
DEVELOPMENTAL CHANGES
- NS favoured changes to help primates compete for angiosperm resources
primate features
- adaptations for locomotion
- opposable thumbs, tails
- hind limb posture
- stereoscopic vision (depth perception), 3 colour vision
- nails
- big brain time
primate phylogeny
ANTHROPOIDS
new world monkeys
- prehensile tails, no opposable thumbs
- no 3 colour vision (minus howlers)
- monogamy
old world monkeys + apes (hominoids)
- sexual dimorphism
- non monogamous
- grasping hands and feet
tarsiers
- BIG EYES. big as brain
- good ears
- long feet and fingers
prosimians
- small brain
- large smelling
- nocturnal
general terms for monkeys
anthropoids: NWM, OWM, apes (humans too)
hominoids: apes (humans too)
hominins: human lineage after divergence from chimps and bonobos
anthropoids
NWM, OWM, apes (humans too)
hominoids
apes (humans too)
hominins
human lineage after divergence from chimps and bonobos
types of foraging
- collection (eg fruit)
- extraction (eg termites)
- hunting
complex foraging
hunting and extractive foraging
- requires learning
- food flow between ages and genders
- food sharing (self-sufficient food production only in adults)
- division of labour
complex foraging: effects of food sharing and labour division
lead to
- reduced sexual dimorphism
- less competition between males
when male parental care is important, males don’t compete as much for reproductive rights
causes for evolution of locomotion in hominins
- environmental changes caused hominins to move to grasslands
theories of bipedalism
possibly…
- kept hominins cooler
- leaves arms free to carry things
- response to increase dependance of offspring
- suspensory locomotion (uncommon) pre-disposed ape lineage to evoke bipedalism
hominin features (4-6 mya)
ANCESTRAL
-small molars
- canines larger
- low brow ridge
- small brain case
DERIVED
- forward location of foramen magnum (brainstem hole)
- small canine teeth
- changed in femur, pelvis
- flatter face
difference between ancestral and derived features
ancestral
- old features
derived
- features we see in ourselves today
hominin features (2-4mya)
3 diff species
generally…
- small bipeds
- small teeth
- flat face
difference between humans and other apes
- fully bipedal
- long juvenile period
- big brain time
- spoken language
when did humans and chimps split? details of split
5-7 million years ago
posture
- foramen magnum (brain stem hole) moves forward
- pelvis repositioned for upright posture. flattened + flared
- abductors to stabilize pelvis
- longer legs, directly under body (fever-tibia alignment)
- narrow foot, larger big toe
neanderthal morphology + origins
- faces that bulge in middle
- large brow ridge
- BIG big brain capacity (> humans)
- stocky, muscly bodies
adaptations may reflect adaptation to the cold
ORIGINS
- up to 400 000 years ago
- europe, western asia
-
mitochondrial DNA + neanderthal
mitochondrial in humans more closely related to each other than to neanderthals
- therefore, no evidence of gene flow with neanderthals based on that part of genome
- evidence of gene flow in autosomal DNA
what does the neanderthal genome sequence tell us?
- non- African humans shares ~2% of genome with neanderthals
- 1/5 of neanderthal genome in scattered over different non-africana genomes today
- modern humans from Africa shared very little
CONCLUSION
- gene flow with neanderthals may have happened after humans left Africa, but before populations in Europe and Asia diversified
Denisovans
more related to neanderthals than AMH
- after divergence from neanderthals, both had occasional gene flow with humans
