environment of evolutionary adaptedness Flashcards
What does Thomas Hobbes argue about the “state of nature” in The Leviathan (1651)?
Hobbes believed life in the state of nature was chaotic and violent, lacking industry, culture, society, and safety. Life was “solitary, poor, nasty, brutish, and short.”
When did orangutans, gorillas, and humans diverge from each other in evolutionary history?
Orangutans: 9–13 million years ago; Gorillas: 8.5–12 million years ago; Humans: 5.5–7 million years ago from the last common ancestor with chimpanzees and bonobos.
How long ago did humans, chimpanzees, and bonobos last share a common ancestor with monkeys?
About 30 million years ago.
How many chromosome pairs do humans and chimpanzees have, and what major difference exists?
Humans: 23 pairs (46 total); Chimpanzees: 24 pairs (48 total). Human Chromosome 2 appears to be a fusion of two ancestral ape chromosomes.
What is the difference between the terms “hominid” and “hominin”?
“Hominid” now includes all great apes (including humans), while “hominin” refers specifically to humans and their bipedal ancestors.
Which hominin species is still extant today?
Homo sapiens (anatomically modern humans).
What are Homo floresiensis and Denisovans?
Homo floresiensis (“hobbits”) were small hominins from Indonesia; Denisovans are a mysterious archaic human species known from limited DNA and fossil evidence in Asia.
From which species did both Neanderthals and modern humans evolve?
Homo heidelbergensis (archaic Homo sapiens).
What are three major adaptive milestones in hominin evolution?
Bipedal locomotion (~7 mya), stone tool use (~3 mya), and large brain development (within the last 2 million years).
What is the hypothesis presented by Timmermann et al. (2022) regarding H. heidelbergensis?
It split into two branches ~500,000 years ago: a northern branch (Neanderthals) and a southern branch (Homo sapiens), each adapting to different climates.
What does genetic evidence suggest about modern humans and archaic species like Neanderthals and Denisovans?
There was interbreeding; many non-African humans carry Neanderthal and/or Denisovan DNA.
When did the first stone tools appear, and when did agriculture emerge?
Stone tools: ~2.6 million years ago
Agriculture: ~10,000 years ago.
What were Pleistocene megafauna, and why are they significant?
Large animals like saber-toothed cats and mastodons that coexisted with early humans. Their extinction may have been due to hunting, climate change, or disease.
How does the human pelvis differ from that of a gorilla, and what does it indicate?
The human pelvis is bowl-shaped and short, supporting upright bipedalism; the gorilla pelvis is tall and blade-like, suited for quadrupedal movement.
How do the femurs of apes, australopithecines, and humans differ in relation to bipedalism?
Human and australopithecine femurs angle inward toward the knees, aiding bipedalism. Ape femurs hang straight down, inefficient for upright walking.
What do the Laetoli footprints show, and why are they important?
3.7-million-year-old bipedal footprints demonstrating early upright walking in hominins (likely Australopithecus afarensis).
What environmental changes may have driven the evolution of bipedalism?
Forest fragmentation into savannahs in Africa created selective pressures for upright walking to travel between trees, spot predators, and carry items.
Name at least five hypotheses for why bipedalism evolved.
Carrying tools/infants, accessing food, thermoregulation, predator avoidance, and wading in water.
what is bipedalism?
a form of locomotion where an animal moves on its two rear (or lower) limbs or legs
How has brain size changed over hominin evolution?
From ~400 cc in australopithecines to ~1500 cc in modern humans and Neanderthals, with a major increase ~500,000 years ago.
What does the reduction in zygomatic arch size in skulls suggest about hominin evolution?
Reduced jaw muscle size (temporalis and masseter) over time, associated with dietary changes and increased cranial capacity in the genus Homo.
