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HUMANS Homo sapiens
On a small branch of the tree of life,
among the Mammals, a group
emerged
Visual, tree dwelling, grasping hands
and feet, most similar to Prosimians
of today
This group radiated
from a common
ancestor <60MYA
1758, Linnaeus named
the group Primate “chiefs of creation”
Named 3 genera based
on limited species Lemur, Simia, Homo
Good fit to current
view – prosimians,
monkeys, apes
In Homo, Linnaeus included
Chimpanzees, Orangutan,
and Humans. Gorillas and
Gibbons were not yet known.
Today all separate genera
Jane Goodall
Divergences (common
ancestors) indicated by
fossils and molecular data
Apes and Old World
monkeys < 30MYA
Humans and Chimps <10 MYA
The human lineage (“Hominan”) contains many extinct species,
exact relationships not certain due to lack of genetic data
Hominans have many distinctive traits
Bipedal locomotion
Precision grip
Tool use
Reduced sex size dimorphism
Reduced jaw, Meat eating
Large Brain
Culture, Language
3.5 MYA
While very closely related to the great apes,
humans are clearly significantly different.
Is this a contradiction?
Recall the Cetacea
Recall: Camels are more closely
related to whales than to horses.
Given sufficient “adaptive opportunity”, change can be rapid
What is the key hominan adaptive “innovation”?
Out of Africa
Australopithecus sp. – 4-2 MYA
Bipedal, brain 30%
“Lucy”
Homo erectus
1.7 MYA
Brain 60%
Migrated as far
as Indonesia
Extinct 200,000 YA
Possible exception – Homo floresiensis (discovered 2004)
Existed on Flores Island as late as 18,000 years ago
Size of Australopithecus
Skull of H. erectus
Various hypotheses
Island induced dwarfism?
http://magma.nationalgeographic.com/ngm/0504/feature1/index.html
Homo neanderthalensis – 200,000 years ago, Europe
Brain 100%
Used fire
Extinct 30,000 years
- DNA
Replaced by
Homo sapiens
Homo sapiens
Oldest fossil - 160,000 years - Ethiopia
Global dispersal
Asia by 50,000 years
New World, 15,000 years
African origin – all genetic variation
One species – could have been different
National Geographic March 2006
National Geographic March 2006
Adaptation (mainly cultural) to a wide variety of habitats - biomes
Primary mode – “hunter-gatherer” for most of history
Strong dependence on natural environment
Omnivory – balance abundance and nutrition
Pastoralism: Evidence of plant and animal domestication <10,000 years
Many groups mixed huntinggathering with small scale
cultivation
Slash & Burn common
Agricultural civilizations <8,000 years
1-4/1-3
Hunter-Gatherer => Pastoralism => Agriculture
Increasing control over resource species, less dependent
on ecosystem controls, change in “knowledge”
Ecosystem forces - primarily antagonistic, nature must be
“dominated” rather than understood
Persistent exponential growth in humans suggests that we have
not yet encountered significant environmental deterioration.
Question: Do we want to?? Do we want to reach KHuman?
No one knows
what KHuman is
Humans have become a dominant force in the biosphere
Ecological Footprint: In addition to total numbers,
level of resource use (culturally variable) by individuals
determine the total impact on the biosphere
Can the earth support our footprint?
1.7/1.5
Recall – biosphere is thin
About 20 mi. thick
“2-dimensional”
Life has altered it greatly
Humans might also
Classifying human impacts –
problem because of multiple
effects and interactions. E.g.,
coal mining – impacts on land,
water, air, energy future
Human Impacts
One classification scheme
1. Ecosystem replacement
a. urban, suburban
b. agriculture, rangeland & soil erosion
c. mining
2. Alteration of existing systems
a. over-harvesting
b. fragmentation
c. non-native species
3. Global impacts
a. chemical pollution
b. nutrient enrichment
c. climate change
Potential consequences – biodiversity loss, reduced “ecosystem
services”, soil erosion, climate & sea level changes
Ecosystem replacement
Human Impacts –1a
Cities
Urban areas
2% of land area
48% of population
Often on productive land
City expansion
- population growth
- urban sprawl
Urban population
1952
1972
1967
Human Impacts –1a
1995
Las Vegas, NV
Human Impacts 1b
Ecosystem replacement
Urban support systems
Cities need resources from large areas
- photosynthesis
Where does food come from?
Agriculture – 77%
Rangeland – 16%
Fisheries – 7%
Over 30% of (non-polar)
land area converted to
agriculture – from forest
and grassland
80% of food produced
by industrialized
agriculture – for people
& animals
7-1/8-1
Human Impacts 1b
Ecosystem replacement
Rangeland
Less productive grasslands used for grazing livestock
40% of land
Replace native grazers
eliminate predators
overstocking
non-native grasses
Human Impacts 1b
Tropical deforestation
Logging of tropical forest
One-time
Weathered soils
Nutrients in biomass
main fate – grazed grassland
Ecosystem replacement
Ecosystem replacement
Human Impacts 1b
Soil Erosion
Recall – soil crucial, takes many 100s, 1000s of years to form
Erosion – natural process – loss/movement of soil due to wind & water
accelerated with plants removed (agriculture, rangeland, deforestation)
Major effort in soil conservation after dust bowl in US
7-6/8-4
Human Impacts 1c
Ecosystem replacement
Mining
Extraction of materials from rock - diverse
Surface & Subsurface
Not sure how much land
surface involved.
Water runoff affected
- acidity, heavy metals
Fossil fuels – burning releases CO2
Alteration of existing systems
Human Impacts 2a
Overharvesting
We still directly harvest from native
ecosystems – e.g., fisheries, forests
Living populations are “renewable”
– can be harvested in the long term
Increasing “traditional” populations stress systems
wood gathering, “bushmeat”
Overharvesting
- decreased sustainable harvest
- risk of extinction
- ecosystem alteration
Human Impacts 2a
Alteration of existing systems
Most fisheries are overharvested
7-4/8-14
Human Impacts 2a
Alteration of existing systems
Most current forestry practices are not sustainable
Short-rotation forestry
6-1/6-4
Human Impacts 2b
Alteration of existing systems
Fragmentation
Remaining systems are
reduced in size, isolated
Viable populations often
require large, continuous tracts
Fragmentation invariably
leads to reduced
biodiversity – often delayed
Fairfax Co., VA
Alteration of existing systems
Human Impacts 2c
Non-native species
Human activities have increased spread of many species
Some have become “invasive” – displacing native species
Purple Loosestrife
5-9/7-9 Argentine Fire Ant
Global impacts
Human Impacts 3a
Chemical Pollution
Thousands of chemicals are emitted by
modern industry – products,
byproducts, and breakdown products
regulation difficult
Generally point sources,
but diffuse in air & water
Some bioaccumulate &
biomagnify
Classic case: DDT
5-12/7-12
Global impacts
Human Impacts 3b
Nutrient Enrichment
We are increasing key plant nutrients, N, P and CO2
CO2 is increasing due to fossil fuel burning & deforestation
N & P for agricultural production
Phosphorus – rocks mined & ground into fertilizer
Nitrogen – industrial N-fixation, planting of legumes
- human N-fixation now exceeds all others annually
All these inputs spread globally
What’s the problem, isn’t it good to increase plant resources?
Global impacts
Human Impacts 3b
Eutrophication – effect of increased nutrients on ecosystems
first studied in aquatic systems from runoff of agriculture
- soil, fertilizer & animal waste
now seen in terrestrial systems
Increased NPP
Reduced biodiversity
Algal blooms
Increased decomposition => reduced O2
Anaerobic - Fish kills, methane production
8-19/9-21
Human Impacts 3c
Climate Change
Elevated CO2, Methane and Nitrous
Oxide from fossil fuel burning and other
sources add greenhouse gases
This can
change
patterns of
weather and
increase
average global
temperature
12-8/12-19
Human Impacts 3c
1979
Ice in polar regions and at
high altitudes declining
- reduces reflection
- rise of sea level
Global impacts
2003
Global impacts
Human Impacts 3c
20,000 YA
17 ft (5m)
W. Antarctic sheet
170 ft (50m)
E. Antarctic sheet
NOAA
Human Impacts 3c
Snows of Kilamanjaro
may be gone in 15 years
Global impacts
Human Impacts 3b,c
Global impacts
Major impact – species are adapted to prevailing levels
of resources, NPP and climate.
Changes in these levels
- fundamentally alter the relative fitness of species
- the range of essentially every species is predicted
to shift. But can they move?
Consequences of human impacts – environmental “problems”
Check out the “Millennium Ecosystem Assessment”
http://www.millenniumassessment.org/en/index.aspx
Loss of Biodiversity
- major consequence of many
human impacts
Many species threatened
Extinction is fast & forever
Speciation takes a while
Biodiversity is a
kind of knowledge,
a “library”
What will you tell
your grandchildren
if we let the gorilla
go extinct?
5-6/7-6
We’ve gotten this far by learning to cooperate
How much farther can we go?
What is your vision of Utopia?
End
The End