This document discusses extinction, both historically and currently. It explores past mass extinction events and examines whether the current extinction rates constitute a sixth mass extinction. While not at the level of past mass extinctions yet, losing threatened species endangers many forms of life. The document also analyzes evidence that early humans drove megafauna to extinction through overhunting. Though human-driven changes can produce artificial selection, species sometimes adapt when released from those pressures. Island ecosystems face especially high extinction risks from human impacts.

1. Extinction:
Past and Present

2. OVERVIEW
• Review
of
Ex+nc+on
• Are
we
in
the
6th
Mass
ex+nc+on?
• Early
humans
and
ex+nc+on
• Can
organisms
adapt
to
changing
environments?

3. EXTINCTION
The average species exists for "
10
million years"
"

4. MASS EXTINCTIONS
A mass extinction is when the
earth loses "
3/4 "
of it’s species"

5. FOUR WAYS TO SURVIVE
MASS EXTINCTIONS
1! Have a wide geographic range"
Marine
bivalves
that
had
large
ranges
were
more
likely
to
survive
the
cretaceous
ex+nc+on

6. FOUR WAYS TO SURVIVE
MASS EXTINCTIONS
2! Be lucky"

7. FOUR WAYS TO SURVIVE
MASS EXTINCTIONS
3! Be an omnivore or scavenger/
Don’t rely on plants "

8. FOUR WAYS TO SURVIVE
MASS EXTINCTIONS
4! Hibernate or diapause "

9. EXTINCTION THROUGH
HISTORY

10. EXTINCTION NOW

11. EXTINCTION NOW
Is
this
the
6
th"
Mass
Ex+nc+on?

12. EXTINCTIONS IN MAMMALS
Ex+nc+on
rates
if
we
lost
Vulnerable
(VU)
Ex#nc#ons
per
Million
Species
Endangered
(EN)
and
Cri+cally
Endangered
(CR)
species
Years
Barnosky
et.al.
2011

13. THE 6th MASS EXTINCTION?
75%
Barnosky
et.al.
2011

14. THE 6th MASS EXTINCTION?
Ex#nc#ons
per
Million
Species
Rate
of
ex+nc+on
if
historical
ex+nc+ons
were
compressed
Years
into
500
years
Actual
rate
of
ex+nc+on
(occurred
over
1000s
of
years)
Barnosky
et.al.
2011

15. What is causing
our current
extinction rates?!

16. The Case Of the Missing
Mega-Fauna

17. HUMAN DISPERSAL ROUTES
North
America
Australia
Tonga

18. MAMMAL EXTINCTIONS
NORTH AMERICA"

19. NORTH AMERICAN
MEGAFAUNA
5000-6000
6000-7000
7000-8000
8000-9000
9000-10,000
10,000-11,000
11,000-12,000
12,000-13,000
13,000-15,000
15,000-17,000

20. A FIELD GUIDE TO NORTH
AMERICAN MEGAFAUNA
American
Mastodon
Giant
Ground
Sloth
Western
Camel
Wooly
Mammoths

21. A FIELD GUIDE TO NORTH
AMERICAN PREDATORS
Saber
Toothed
Cat
Short
Faced
Bear
Dire
Wolf
Teratorns

22. MISSING MEGAFAUNA
Between 12,000-9,000 mya"
70 %
"
of North American
Species Went Extinct"

23. EXTINCTION
• Climate
warming
• Vegeta+on
changes
• Human
se;lement?

24. HUMAN DISPERSAL ROUTES

25. THE BERING LAND BRIDGE
Bering
Land
Bridge

26. HUMAN DISPERSAL ROUTES
Mari#me
Route
Overland
Migra+on

27. WAS IT OVERKILL?
Evidence
For
Human
Overkill:
• Ex+nc+ons
coincide
with
first
confirmed
human
seZlements
• Most
ex+nct
species
evolved
from
American
ancestors
(no
prior
contact
with
humans)
Evidence
Against
Human
Overkill:
• Small
human
popula+on
size
at
the
+me
• Few
human
archaeological
sites
with
ex+nct
mammal
remains

28. WAS IT OVERKILL?
AUSTRALIA!

29. AUSTRALIAN WILD LIFE
100,000 YEARS AGO
Diversity
of
large
terrestrial
vertebrates
in
mid-­‐
Pleistocene
(<100,000ya)
• 57
marsupials
>10kg
• Varanid
lizards
(e.g.
komodo
dragons)
• Large
flightless
birds

30. FIELD GUIDE TO AUSTRALIAN
WILDLIFE

31. FIELD GUIDE TO AUSTRALIAN
WILDLIFE

32. AUSTRALIAN MARSUPIAL
EXTINCTIONS
Rep#les
>10
kg:
(3/3
ex#nct)
Flightless
Birds:
1/3
Marsupials
0
–
10
kg:
(19/19
ex#nct)
Marsupials
10
–
100
kg:
(22/38
ex#nct)

33. THE KINGDOM OF TONGA

34. THE KINGDOM OF TONGA

35. THE KINGDOM OF TONGA
Ex+nc+on
of
forest
birds
on
the
island
of
Eua
(Tonga)

36. HAWAIIAN ISLANDS
Bird
ex+nc+ons
aber
Polynesian
seZlement:
60
Bird
Ex+nc+ons
aber
European
SeZlement:
20-­‐25

37. THE GALAPAGOS
GALAPAGOS ISLANDS ISLANDS!
(colonized by humans in 1535 AD)"
"

38. GALAPAGOS ISLANDS
Ex+nc+ons
before
1500:
0-3
Ex+nc+ons
a"er
1500:
20-24

39. ISLANDS: EXTINCTION HOT
SPOTS
Islands
outpace
con+nents
in
ex+nc+on
rates

40. Can Species
Adapt to Human
Selection?"

41. SELECTION ON
CORRELATED TRAITS
Feather Length"
Beak Width"
Beak Depth"
Beak Depth"

42. CAN PLANTS EVOLVE TO MATCH
LOCAL CLIMATE?
Log
(Leaf
Thickness)
Reproduc#ve
Stage
High ! Low !
Fitness! Fitness!
Low ! High !
Fitness! Fitness!
Log
(Leaf
Number)
Log
(Leaf
Number)

43. WINDEMERE LAKE,
ENGLAND!

45. FISHING IN LAKE WINDEMERE
1963
:
Peak
of
Gill
net
fisheries
Net
Fisheries
No
Fishing
Gill
Nets
(12th
Century
–
1921)
1921-­‐1944
1944-­‐1980

46. GROWTH RATE AND FISHING
SELECTIVE PRESSURE
Gill
nets
have
holes
of
a
standard
size
SMALL"
Fish
survive
this
ar+ficial
selec+on

47. GROWTH RATE AND FISHING
SELECTIVE PRESSURE
Predators
and
cannibals
are
important
sources
of
mortality
for
pike
LARGE"
Fish
survive
this
natural
selec+on

48. GROWTH RATE AND FISHING
SELECTIVE PRESSURE
(Edelene
et.al.
2007)

49. KEY POINTS
We aren’t quite to the 6th Mass Extinction"
But…
Losing
threatened
species
will
bring
us
close
to
mass
ex+nc+on
levels

50. KEY POINTS
Prehistoric
humans
exploited
other
species
much
as
we
do
today

51. CAN PLANTS EVOLVE TO MATCH
LOCAL CLIMATE?
Island
species
are
at
greater
risk
for
ex+nc+on

52. KEY POINTS
Anthropogenic change can cause artificial
selection "
But…
When
leb
alone,
species
trait
values
may
return
to
their
previous
state

53. QUESTIONS?"