GEOG 205 Lecture Notes - Lecture 17: Radiocarbon Dating, Short-Faced Bear, Laurentide Ice Sheet

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13 Mar 2013
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GEOG 205 Global Change: Past, Present and Future Winter 2013
March 13th, 2013: Megafaunal Extinctions
there are posts on mycourses that clarify questions/problems for the assignment due next class
(Monday)
film from Monday covered material going to cover today
there are famous extinctions that have occurred over time dinosaurs about 190 million years
ago
what caused the extinction? human? no, they were not around at the same time
o there were mammals around at the same time, but not humans
o only showed up at the beginning of the quaternary
by 11 000 years ago there was another major extinction during the last glacial maximum
mammal content of the earth was much larger
what was lost? lots of animals lost below the laurentide ice sheet some lost around the world,
others only in North America
o saber tooth cat, American lion, sloths, short faced bear, mastodon & woolly mammoth
number of mammal genera lost peaked around 10 000 years ago what was happening then?
o beginning of the Holocene, so things were warming up ice sheets melting, proglacial
lakes, permafrost melting
o warming of permafrost leads to collapses of land, shifts of ecosystems, shifts in biodomes
o are these changes enough to extinct all of those animals?
megafauna were present throughout many fluctuations in temperature
Africa suffered the least in extinctions, but humans were always there
because humans evolved in Africa could animals have adapted to the human presence?
some argue humans rapidly had developed rather effective technologies & arrived in NA with
them ie/ clovis points
additional factors to consider: loss of habitat modifiers (ecological/ecosystem engineers)
o ecological engineer example = alligator it makes depressions that in the dry season hold
water which allow for the survival of a number of other species that need water that
otherwise wouldn’t have it in the dry system
o elephants in Africa remove trees; without, species that are adapted to that habitat
wouldn’t survive
o a cascade effect happens mammoth loss = habitat loss = loss of other species; loss of
prey species = loss of predator species
other factors: predator competition with humans & thus loss of predators
o loss of predators means unstable prey populations so the population crashes
o this was simultaneous with climate change (causes habitat changes)… perhaps all of these
pressures together?
carbon dating is limited hard to get solid dates past 40 000 years ago
Europe
o has great evidence & there is lots of pictorial evidence
o early European architecture
more than 15 tons of bones from the remains of 95 mammoths needed to construct
bone huts were they killing mammoths or did they find the bones? who knows.
study of European site with cones of extinct animals show they occur as often in
isolation of evidence of human occupation as in sites that contain archaeological
remains
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Document Summary

No, they were not around at the same time there were mammals around at the same time, but not humans: only showed up at the beginning of the quaternary. By 11 000 years ago there was another major extinction during the last glacial maximum. Mammal content of the earth was much larger. What was lost? lots of animals lost below the laurentide ice sheet some lost around the world, others only in north america: saber tooth cat, american lion, sloths, short faced bear, mastodon & woolly mammoth. Megafauna were present throughout many fluctuations in temperature. Africa suffered the least in extinctions, but humans were always there. Because humans evolved in africa could animals have adapted to the human presence? some argue humans rapidly had developed rather effective technologies & arrived in na with them ie/ clovis points. Europe: has great evidence & there is lots of pictorial evidence, early european architecture. Geog 205 global change: past, present and future.

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