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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