Human Evolution — Flashcards & Quiz

Q1: What are the key trends in hominin evolution?

Key evolutionary trends from early hominins to modern humans: 1) Bipedalism — upright walking (foramen magnum moves to base of skull, pelvis widens). 2) Brain size increase — ~400 cm³ (Australopithecus) to ~1400 cm³ (Homo sapiens). 3) Jaw and tooth reduction — smaller jaw, reduced canines, changes in tooth enamel (diet shift). 4) Tool use and complexity — Oldowan → Acheulean → Mousterian → Upper Palaeolithic. 5) Language and symbolic thought. 6) Extended childhood and social complexity.

Q2: Compare the "Out of Africa" and multiregional hypotheses of modern human origins.

Out of Africa (Recent African Origin): modern Homo sapiens evolved in Africa ~200,000 years ago and migrated outward, replacing other hominin populations (Neanderthals, Denisovans) with limited interbreeding. Supported by: greater genetic diversity in African populations, mitochondrial DNA evidence, oldest H. sapiens fossils in Africa. Multiregional hypothesis: modern humans evolved simultaneously across multiple regions from local H. erectus populations connected by gene flow. Current evidence overwhelmingly supports Out of Africa with some interbreeding.

Q3: What evidence suggests that Homo sapiens interbred with Neanderthals?

Evidence for interbreeding: 1) Genomic analysis shows 1-4% Neanderthal DNA in non-African modern humans. 2) Specific Neanderthal gene variants persist because they were advantageous (immune genes, skin pigmentation, cold adaptation). 3) A 40,000-year-old human jaw from Romania showed 6-9% Neanderthal ancestry (recent hybrid). 4) Denisovan DNA (up to 5%) found in Melanesian and Australian Aboriginal populations. This proves reproductive contact occurred during the Out of Africa migration.

Q4: Describe the key Australopithecus species and their significance.

Key species: 1) A. afarensis ("Lucy", ~3.9-2.9 MYA) — earliest well-known bipedal hominin, small brain (~430 cm³), East Africa. 2) A. africanus (~3.3-2.1 MYA) — slightly larger brain, South Africa. 3) A. sediba (~2 MYA) — mix of Australopithecus and Homo features, potential transitional form. Significance: Australopithecines demonstrate that bipedalism evolved long before large brains, challenging the idea that intelligence drove human evolution.

Q5: What distinguishes Homo erectus from earlier hominins?

Homo erectus (~1.9-0.1 MYA) key features: 1) Larger brain (~900 cm³, range 600-1100). 2) More modern body proportions — taller, longer legs. 3) First hominin to leave Africa (found in Asia, Europe). 4) Used Acheulean stone tools (hand axes). 5) Evidence of controlled fire use. 6) Reduced sexual dimorphism compared to Australopithecines. H. erectus was the longest-surviving hominin species (~1.8 million years).

Q1: Large brain size evolved before bipedalism in the hominin lineage.

Answer: FALSE

BIPEDALISM evolved BEFORE significant brain expansion. Australopithecus afarensis (Lucy, ~3.2 MYA) was bipedal but had a brain size similar to a chimpanzee (~430 cm³). Major brain expansion occurred later in the Homo lineage.

Q2: The "Out of Africa" hypothesis proposes that modern Homo sapiens evolved in Africa and migrated to other continents.

Answer: TRUE

The Out of Africa (Recent African Origin) hypothesis states that modern H. sapiens evolved in Africa ~200,000 years ago, then migrated outward and replaced other hominin populations with limited interbreeding. This is supported by genetic and fossil evidence.

Q3: Modern non-African humans contain no DNA from archaic hominins like Neanderthals.

Answer: FALSE

Non-African modern humans carry 1-4% Neanderthal DNA from interbreeding during the Out of Africa migration (~50,000-60,000 years ago). Some Asian and Melanesian populations also carry Denisovan DNA (up to 5%).