Lecture 29 Flashcards
(29 cards)
what are some key events in hominin evolution?
- hominins split from apes about 8 mya
- difficulties in developing a complete phylogeny are the result of an incomplete fossil record and homoplasy
- hominin fossils are known as homo, parathropus or australopithecus
what is homoplasy?
the development of organs or other bodily structures within different species, which resemble each other and have the same functions, but did not have a common ancestral origin.
evolves independently in different species
when did hominins emerge?
- near the end of the miocene
- during a time of dramatic climate change
- they adapted to new more open environment in many ways
how did hominins adapt to a new more open environment
- walked on two legs (bipedal motion)
- changes in teeth/jaw. changes in diet led to this
- increasing sophisticated tool making, indicator of cognition. could have been driven by changes in diet
are there fossils that indicate bipedialism?
yes
what were environmental change during hominin evolution and its signifigance
- temperature dropped
- africa got less rainfall
- drier woodlands and grasslands expanded, which opened up a new niche
- seasons of rain and drought, and being able to walk onow helped them in these areas (gave an advantage)
- environment more predicatable
what are key features of the emergence of homo?
- early members of homo lost tree climbing abilities
- had long legs and other traits for effecient walking and running
what was the impact of the ability for homo to run?
running may have changed hunting practices and shifted toward a meatier diet
narrow rib cage and small molars indicated that homo ate more meat
what is the hypoothesis between a dietary shift and homo evolution
dietary shift may have been critical to evolving larger brains, which require huge amounts of energy
where did hominins expand out of originally?
africa 2 mya
when fossils of homo in asia were found what suggested expansion of different lineages of homo from africa
the fossils in asia had morphological variation compared to those in africa, indicating some sort of lineage expansion
what was the continued chages of more recent homo species
brain enlargement, complex cognition, and lots of migration
what is unique morphology of the more recent homo species’s
taller and narrower body, smaller face, teeth, jaws, chin, large brain
what was the unique cognitive abilities indicated by for the recent homo species
worldwide expansion, accerlearing change in tools, art, language
where did neanderthals evolve?
- in europe and asia
- adapted to the harsh ice age climate
- large brains
- had broad shoulders and hips and a muscular build (these were adaptations, not the primitve form, allowed them to be better suited to environment)
- neanderthal artifcats reveal sophisticated behavior (also had evidence theyburied their dead)
are denisovans their own species?
no, but there is dna analysis that suggests their is enough differences to consider denisovans to be a distinct lineage.
how is there evidence for hybridization between denisovan and neanderthals and humans?
- the presence of small amounts of both denisovan and neanderthal dna in humans indicates hybridization
- so might have mated with them and then weeded out most of their genome
- evidence that modern homo sapiens were better suited to environment and caused their extinction
where does the evidence point to where humans originated from?
africa and then expanded through the continent before migrating to other countries
what does evidence suggest about neanderthals, denisovans, and homo sapiens?
- evidence suggests that humans, neanderthals and denisovans repersent separate lineages descending from a common ancestor
- there was subsequenct interbreeding between the lineages
- humans have presence of neanderthal and denisovan dna in their genome
what are the driving forces behind evolution of hominin brains?
ecological, social, and cultural factors
why is it thought that language is at the core of human nature?
- all languages have commonalities (syntax)
- language is an adaptation shaped by natural selection
- researchers are studying multiple lines of inquiry: language related behaviors in nonhuman primates, the search for genes underlying human language, the evolution of the brain itself
what is syntax?
the arrangement of words and phrases to create well formed sentences
What is the key point of what happened as humans expanded around the globe?
as humans expanded around the glove, they went thorugh multiple bottlenecks and populations diverged genetically via drift (classic isolation by distance pattern)
is allele frequency differentiation in humans low or high?
- relatively low
