Chapter 13: Homo Sapiens and the Evolution of Modern Human Behavior
Modern Humans in Africa before 60 Ka
●Anatomically modern Homo sapiens have several derived features w contemporary humans:
○Small, flat face w/ protruding chin
■Didn’t use teeth as tools as much → smaller face/teeth
■Jutting chin – significant? ○Rounded skull
■High foreheads
■Rounded back of skull
■Reduced browridge
○Brain capacity of 1350cc+
■Smaller than Neanderthals, greater than any other hominin
○Less robust postcranial skeleton
■Longer/thinner limbs/hands
■Thinner-walled bones
■Short, thick pubic bones
■Distinct shoulderblades
■Relied less on physical strength and more on tools/innovation
○Long limbs, short trunks
■Similar proportions to contemporary warm-climate people
●315Ka: skulls in Morocco – similar faces to modern humans, but w/ long/low skulls of H. heidelbergensis
●160Ka: Herto skulls– longer/more robust than modern skulls w/ prominent brow ridges and other earlier traits, but also have high/rounded braincase of modern humans
○Stone tools similar to H. heidelbergensis
●Modern humans and Neanderthals did live in the same area at the same time
African Archaeological Record for the Later Pleistocene
●Modern human behavior more complex/variable
●250-40Ka – stone tools mostly Mode 3 type
○These industries are the Middle Stone Age (MSA)
●Complex adaptive tech in association with MSA sites:
○Blades: long, thin stone tools found commonly after 40Ka, but also evidence around 280-2240Ka
■Part of the Mode 4 tools
○Symmetric, leaf-shaped points ■Used pressure flaking where makers used hard, pointed tool to remove small flakes → greater control over flaking process
○Tool made up of small stone microliths w/ sharp edge on one side, flattened surface on other side
■Part of Mode 5 tools
■Used as arrow or spear points
●These humans used more complex techniques in MSA era
○Heat-treated silcrete stone to make it easier to work with/make tools with
○Used bones to make tools sometimes
○Shelters/hearths
●Large social networks
○Transported raw material long distances
●Decoration
○Made decorative carvings, beads, used pigment
○Painted shells + strung them on cords/into clothes
○Decorated ostrich eggshells, which modern foragers use as containers for water
●First evidence of complex behavior was much after people started to look modern
○Could have been genetic and/or cultural change that → complex behavior
○Agriculture adopted ~10Ka → sedentary villages, social inequality, societies, other innovations
■Could have been some similar innovation that led to evolution of complex behavior, just not preserved in fossil record
Out of Africa
●Modern human behavior evolved at 250Ka, by 70Ka fully modern ppl were living on southern coast of Africa
●Major expansion out of Africa ~60Ka
●By 30Ka, Neanderthals disappear, modern humans present in Africa/Eurasia
Fossil Evidence
●Some modern human fossils found outside Africa dated pre-60Ka, but these are not solidly dated
●Many modern human fossils found in China, Laos, Borneo, Australia, across Europe dating to after 63Ka
Genetic Evidence
●Genetic variation patterns extracted from fossils + living ppl gives lots of evidence:
○Modern humans evolved in Africa b/n 300-90Ka
○Modern humans outside Africa descended from 1+ populations that left Africa b/n
120-40Ka
○Some interbreeding b/n modern humans and Neanderthals/Denisovans ●Gene trees support African origin of contemporary humans
●Most modern humans are descended from ppl who left Africa 80-60Ka
●Analyses of median MRCA:
○Deepest pop split in living humans (Khoe-San ppl of southern Africa and all other
humans) happened ~350-260Ka
■Lower bound for timing of modern humans
○Second-deepest pop split happened ~200Ka, b/n central African hunter-
gatherers and all other humans
○Third split divided Africans and humans who left Africa ~80-60Ka
■This split gave rise to majority of contemporary non-Africans
●All modern humans descended from small population
○Calculations of drift vs mutation rate lets us estimate past pop sizes
●Genetic variation decreases w/ increasing distance from Africa
○
●Microsatellite Loci: noncoding, repetitive, variable DNA sequences used for individual identification
●In Eurasia, modern humans encountered Neanderthal/Denisovan populations
○Contemporary Africans only have trace amounts of Neanderthal DNA but all Eurasian/Pacific populations have ~2%
○East Asians have <0.5% Denisovan genes, Oceanic people have 3-6%
●Neanderthals who contributed genes to contemporary non-Africans were closely related to Neanderthals for whom we have ancient DNA sequences, but not for Denisovans
○Can identify DNA stretches ( haplotypes) in modern humans that are similar to corresponding stretches in Neans/Denis
○Introgression: incorporate 1 haplotype into genome of another pop
■Introgressed Nean haplotypes in humans match Nean ancient genomes
■Introgressed Denis haplotypes are not as closely matched to Denis genome found in Siberian cave
●Denisovans who mated w humans diverged from Denisovans from
the cave ~340Ka
●Some highly divergent haplotypes in contemporary African hunter-gatherers suggest ancestors mated w/ 1+ early hominn pops ~40Ka
○Less conclusive evidence for this
●Interbreeding w Neanders happened early in spread of modern humans ~60Ka, continued for a long time
○Happened ~50-36Ka
Modern Humans in Africa before 60 Ka
●Anatomically modern Homo sapiens have several derived features w contemporary humans:
○Small, flat face w/ protruding chin
■Didn’t use teeth as tools as much → smaller face/teeth
■Jutting chin – significant? ○Rounded skull
■High foreheads
■Rounded back of skull
■Reduced browridge
○Brain capacity of 1350cc+
■Smaller than Neanderthals, greater than any other hominin
○Less robust postcranial skeleton
■Longer/thinner limbs/hands
■Thinner-walled bones
■Short, thick pubic bones
■Distinct shoulderblades
■Relied less on physical strength and more on tools/innovation
○Long limbs, short trunks
■Similar proportions to contemporary warm-climate people
●315Ka: skulls in Morocco – similar faces to modern humans, but w/ long/low skulls of H. heidelbergensis
●160Ka: Herto skulls– longer/more robust than modern skulls w/ prominent brow ridges and other earlier traits, but also have high/rounded braincase of modern humans
○Stone tools similar to H. heidelbergensis
●Modern humans and Neanderthals did live in the same area at the same time
African Archaeological Record for the Later Pleistocene
●Modern human behavior more complex/variable
●250-40Ka – stone tools mostly Mode 3 type
○These industries are the Middle Stone Age (MSA)
●Complex adaptive tech in association with MSA sites:
○Blades: long, thin stone tools found commonly after 40Ka, but also evidence around 280-2240Ka
■Part of the Mode 4 tools
○Symmetric, leaf-shaped points ■Used pressure flaking where makers used hard, pointed tool to remove small flakes → greater control over flaking process
○Tool made up of small stone microliths w/ sharp edge on one side, flattened surface on other side
■Part of Mode 5 tools
■Used as arrow or spear points
●These humans used more complex techniques in MSA era
○Heat-treated silcrete stone to make it easier to work with/make tools with
○Used bones to make tools sometimes
○Shelters/hearths
●Large social networks
○Transported raw material long distances
●Decoration
○Made decorative carvings, beads, used pigment
○Painted shells + strung them on cords/into clothes
○Decorated ostrich eggshells, which modern foragers use as containers for water
●First evidence of complex behavior was much after people started to look modern
○Could have been genetic and/or cultural change that → complex behavior
○Agriculture adopted ~10Ka → sedentary villages, social inequality, societies, other innovations
■Could have been some similar innovation that led to evolution of complex behavior, just not preserved in fossil record
Out of Africa
●Modern human behavior evolved at 250Ka, by 70Ka fully modern ppl were living on southern coast of Africa
●Major expansion out of Africa ~60Ka
●By 30Ka, Neanderthals disappear, modern humans present in Africa/Eurasia
Fossil Evidence
●Some modern human fossils found outside Africa dated pre-60Ka, but these are not solidly dated
●Many modern human fossils found in China, Laos, Borneo, Australia, across Europe dating to after 63Ka
Genetic Evidence
●Genetic variation patterns extracted from fossils + living ppl gives lots of evidence:
○Modern humans evolved in Africa b/n 300-90Ka
○Modern humans outside Africa descended from 1+ populations that left Africa b/n
120-40Ka
○Some interbreeding b/n modern humans and Neanderthals/Denisovans ●Gene trees support African origin of contemporary humans
●Most modern humans are descended from ppl who left Africa 80-60Ka
●Analyses of median MRCA:
○Deepest pop split in living humans (Khoe-San ppl of southern Africa and all other
humans) happened ~350-260Ka
■Lower bound for timing of modern humans
○Second-deepest pop split happened ~200Ka, b/n central African hunter-
gatherers and all other humans
○Third split divided Africans and humans who left Africa ~80-60Ka
■This split gave rise to majority of contemporary non-Africans
●All modern humans descended from small population
○Calculations of drift vs mutation rate lets us estimate past pop sizes
●Genetic variation decreases w/ increasing distance from Africa
○
●Microsatellite Loci: noncoding, repetitive, variable DNA sequences used for individual identification
●In Eurasia, modern humans encountered Neanderthal/Denisovan populations
○Contemporary Africans only have trace amounts of Neanderthal DNA but all Eurasian/Pacific populations have ~2%
○East Asians have <0.5% Denisovan genes, Oceanic people have 3-6%
●Neanderthals who contributed genes to contemporary non-Africans were closely related to Neanderthals for whom we have ancient DNA sequences, but not for Denisovans
○Can identify DNA stretches ( haplotypes) in modern humans that are similar to corresponding stretches in Neans/Denis
○Introgression: incorporate 1 haplotype into genome of another pop
■Introgressed Nean haplotypes in humans match Nean ancient genomes
■Introgressed Denis haplotypes are not as closely matched to Denis genome found in Siberian cave
●Denisovans who mated w humans diverged from Denisovans from
the cave ~340Ka
●Some highly divergent haplotypes in contemporary African hunter-gatherers suggest ancestors mated w/ 1+ early hominn pops ~40Ka
○Less conclusive evidence for this
●Interbreeding w Neanders happened early in spread of modern humans ~60Ka, continued for a long time
○Happened ~50-36Ka
