Info

SOURCE: Jeffrey S. Levinton, "Extinction, Rates of," Encyclopedia of Biodiversity (San Diego,

NOTES: (i) Extinctions/standing taxonomic richness x100.

Table 5: Milestones in hominid cultural evolution

6 million to 2 million years bce

• Aridipithecus ramidus, the oldest known possibly bipedal ape represented by fossils from sites in Ethiopia. These first chimp-sized pre-humans with an upright posture appearing in the East African Rift Valley are followed approximately 4 million years ago by the better-known Australopithecus africanus, a small-brained upright walker from the sites in northern Kenya; and Australopithecus afarensis, a big-faced apelike species to which the famous "Lucy" belonged.

2 million years BCE

• Homo erectus had a brain of 1,100 cc (three-quarters the size of anatomically modern humans), suggesting that having a large brain helped in acquisition of skills like tool using, which is not unique to humans (used by finches, chimps), tool making, and the use of fire, which is unique to humans (making possible artifacts ranging from flint axes to, more recently, computers). 98% of hominid history is defined by hunting/gathering and foraging/scavenging modes of life.

130,000 bce

• Modern anatomy is first recognized for early Homo sapiens (the earliest fossils are documented in Africa with an estimated founding population of c. 10,000 people).

30,000 bce

• Worldwide range of fully modern humans, Homo sapiens sapiens; theories suggest that both the ability to use language and the ability to think objectively about oneself ("self-consciousness") depended on brain growth and may have had a crucial role in ensuing human success.

• 15,000 bce => Oldest grinding stones (with world population at c. 8 million)

9000 bce => Domestication of sheep 8500 bce => First semi-permanent settlements 8000 bce => Barley domesticated 6500 bce => Towns of a few thousand (e.g. Jericho) 6000 bce => Pottery 5500 bce => Irrigation 4500 bce => The (pottery-making) wheel 3500 bce => Uruk, Sumer, with 50,000 inhabitants

Fifteenth-twenty-first century ce

• Modernity (Early, High, Late, Post). industrial-capitalist revolution, colonialism, imperialism; 80 years from Darwin's Origin of Species to Hiroshima and Nagasaki; Cold War and colonization of space (Sputnik vs satellite, moon landing); population bomb and population explosion (1,000% world population increase between 1600 and 2000); globalization (revolution in transport and communications technologies, compression of space and time); biotechnology and genetic engineering; more than 6 billion humans use almost 50% of net productivity of photosynthesis (NPP) of land ecosystems and 30% overall; destruction of rain forests and globalization of environmental degradation, destruction of ozone layer; doubling of cO2, global warming; climate change; widespread pollution (nuclear, chemical, biological), acceleration of soil erosion, desertification; mass extinction of species and the genuine possibility of a global collapse of biodiversity in the near future (ecological overshoot); global ecological restoration?

SOURCE: Adapted from Clive Ponting, A Green History of the World: The Environment and the Collapse of Civilizations (London: Penguin Books, 1991), p. 53.

Table 6: Human forces driving changes in biological diversity (before 1500; 1500 to 1800; since 1800)

Before 1500 (world conquest, terrestrial colonization, military expansion of empires)

• Hunting gathering, and scavenging (e.g. megafauna overkill)

• Domestication of plants and animals; intensification of agriculture and trade

• Intensification of agriculture by plowing

• Offshore traffic and trade

• Building up of large empires (e.g. Persian, Roman, and Mongol), with considerable expansion of communication and transportation systems

• Long-range wars and military expansion; Establishment of "market economies" (e.g. Venice)

1500 to 1800 (early orthodox modernity: mercantile capitalism, early colonialism)

• Exploration, discovery, and colonization by Europeans of other territories and continents (e.g. the "Columbian Exchange")

• Establishment of new market economies and trading centers (e.g. Amsterdam, London) favoring the globalization of trade exchange

• Revolution in food customs (e.g. increased use of tea, coffee, chocolate, rice, sugar, potatoes, corn, beef, and lamb)

• International introductions of exotic spices through activities of acclimatization societies, botanical gardens and zoos, and for agricultural, forestry, fishery, or ornamental purposes

• Large-scale labor migration

Since 1800 (high, late, and post-modernity: Industrial Revolution, high colonialism, imperialism, arms race, economic liberalism, global rift, demographic explosion)

• Rapid improvement of transportation systems (roads, railways, navigation canals)

• Large-scale industrial production and emergence of transnational corporations (TNCs)

• Construction of large engineering works for irrigation and hydropower

• High-input, chemicalized agriculture; mechanized fisheries and forestry

• World wars and displacement of human populations

• Tropical deforestation and resettlement schemes

• Afforestation of arid lands with exotic species

• Increased urbanization and creation of habitats characterized by cosmopolitan species

• Release of genetically engineered organisms and synthetic ecotoxins, bioaccumulation

• Anthropogenic climate change and destruction of atmosphere ozone layer

SOURCES: Modified after V.H. Heywood, R.T. Watson, United Nations Environment Programme, Global Biodiversity Assessment (Cambridge and New York: Cambridge University Press, 1995), p. 719. And F. di Castri, "History of biological invasions with special emphasis on the Old World," in J.A. Drake, H.A. Mooney, F. di Castri, R.H. Groves, F.J. Kruger, M. Rejmanek, and M. Williamson (eds), Biological Invasions: A Global Perspective, SCOPE 37 (Chichester and New York: John Wiley, 1989, on behalf of the Scientific Committee on Problems of the Environment [SCOPE] of the International Council of Scientific Unions), pp. 1-26.

Table 7: Late Pleistocene megafauna extinction - (percentages and weights in kg)

All herbivores

1,000 (kg)

75% of herbivores

100-1,000 (kg)

41% of herbivores

5-100 (kg)

<2% of herbivores

< 5 (kg)

SOURCE: Adapted from Peter J. Bryant, "Extinction and Depletion from Over-Exploitation," The Origin, Nature and Value of Biological Diversity, the Threats to Its Continued Existence, and Approaches to Preserving What Is Left [A Hypertext Book] (Irvine, CA: School of Biological Sciences University of California, Irvine, 1997).

NOTE: The Late Pleistocene and Late Quaternary megafauna extinctions occurred at different times on different landmasses and oceanic islands. The timing of this recent mass extinction spasm coincides with arrival of the first anatomically modern humans.

Table 8: Onset dates of major extinction episodes

Years before present

Table 8: Onset dates of major extinction episodes

Africa and SE Asia

50,000

Australia

45,000

North Eurasia

13,000

North America

11,000

South America

10,000

West Indies

4,000

Aotearoa (NZ)

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