it's literally just biology

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the story is I need to STUDY but I'm distracted... bc I wanna hatch this egg
so brilliant plan, I'm just gonna write my notes here HAHA
bless anyone who happens upon this crap, learn yourself some biology

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every time I open this book I'm reminded of why I hate everything larger than a molecule

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Eutherians - complex placentas, longer pregnancy (complete development in uterus)
Primates - hands and feet for grasping, flat nails and "fingerprints", large brain, short jaws, extensive parental care and social behavior
Early primates were tree-dwellers - required hands/feet to grasp branches, opposable thumbs, 2 forward-facing eyes enhance depth perception
Lemurs/lorises/bush babies, tarsiers, anthropoids

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New World monkeys reached South America from Africa by catching rides on driftwood, ya'll 15th century European explorers got nothing on that

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Monkeys - diurnal (daytime), social bands, originated in Africa/Asia, New World monkeys colonized South America and radiated separately → 2 groups
New World - prehensile tail, nostrils open to the sides, strictly arboreal
Old World - no prehensile tail, nostrils open downward, arboreal or ground-dwelling
Apes (includes humans) - diverged from Old World monkeys
Nonhuman apes: larger than monkeys, long arms, short legs, no tail, large brain and flexible behavior

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Humans - stand upright, bipedal, larger brain (capable of complex thought), reduced jawbones/muscles, shorter digestive tract
Difference in expression of a small number of regulatory genes between humans and chimpanzees can cause vast phenotypic differences between the two species

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hmmm don't like that wording... this is better

Vast phenotypic differences between two species can be due to differences in the expression of a small number of regulatory genes

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Hominins - extinct species closely related to humans, share some derived characters of humans
Reduced canine teeth, flat faces, somewhat upright/bipedal (foramen magnum hole is located underneath the skull → holds head directly above body, bipedal pelvis/leg/feet structure)
Not all derived characters of humans evolved in tight unison (eg. bipedalism and brain size)
Early hominins are not chimpanzees or evolved from them - chimpanzees and humans shared a common ancestor prior to diverging and acquiring their own derived characters
Human evolution is not linear or gradually progressive - H. sapiens are the only surviving member of a highly branched evolutionary tree

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Australopiths - later hominins
“Gracile” australopiths - light feeding equipment → soft foods
A. africanus - fully bipedal, human-like hands/teeth, small-ish brain
A. afarensis - short, softball-sized brain and long lower jaw, long-ish arms enable arboreal locomotion, bipedal
“Robust” australopiths - sturdy skulls, powerful jaws, large teeth → for hard, tough food

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Bipedalism - naturally selected for as climate dried and forests gave way to savannahs
However, early hominins that were somewhat bipedal lived in mixed habitats, not savannahs
Bipedalism did not evolve in a linear fashion - some hominins could both walk and climb trees, others spent more time doing one, etc.
Hominins living in dry environments were the first to walk long distances on 2 legs

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Manufacture and use of complex tools - early hominins may have used stone tools to cut flesh off of animals, evolved before large brain

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it occurs to me that never in my notes do I ever write down the dates (err... numbers of years ago) of any of these evolutionary occurrences, and the reason is just that
I don't care enough ALFKDJF
no one can make me memorize numbers like that... not happening.......

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Early Homo fossils
H. habilis - shorter jaw and larger brain than australopiths, used stone tools
H. ergaster - even larger brain, long legs w/ hip joints for long distance walking, short and straight fingers (nonclimbers)
Lived in drier environments, more complex stone tools
Smaller teeth (ate more meat, less plant), meal prep?
Decrease in extent of sexual dimorphism (size of males vs. females) → more pair-bonding than male-male competition, long-term parental care of young
H. erectus - first to migrate out of Africa

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Neanderthals - thick-boned, prominent brow, larger brain than humans, buried their dead, made hunting tools
Humans and neanderthals shared a common ancestor (not directly descended)
Some gene flow between humans and neanderthals

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I'm reminded of the time that I took a course in life science pedagogy, where the final project was to make a presentation and teach the class about an assigned topic. smh was unlucky enough to get assigned the topic I was least familiar with on that list....... neanderthals
DEFINITELY BS'd THAT ASSIGNMENT IN ONE NIGHT........ turns out I'm a real convincing teacher

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Homo sapiens - ancestors originated in Africa, less pronounced brow, more slender
Spread outside of Africa in waves → Asia, then Europe, then Australia
H. floresiensis - shorter height and smaller brain than H. sapiens, but lived at the same time
If it’s a new hominin species, then the “shrinkage” may be due to island isolation - natural selection favors smaller brain size to reduce energy consumption

Forums The Undercurrent it's literally just biology

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