The Oligocene to the Quaternary: climate and biology - Climate Change: Biological and Human Aspects - page 185

not became extinct (Miller et al., 2005). A similar story emerges from the work of
Gavin Prideaux, John Long and colleagues (2007).
Whereas this affirms the role of human activity in causing environmental change
and so being an extinction driver, it does not, as it may at first seem, discount the impact
synergistically of climate change together with that of humans on the extinction event.
The above testing of climate change against the 13 C record only demonstrates that
previous climate did not affect the ecology sufficiently to affect the animals' diets.
It could be that human-induced (anthropogenic) ecological change did a certain
amount of environmental modification and that this could have been furthered by
climate change at the time. An alternative variation could be that anthropogenic
ecological change put a certain level of pressure on the species and that climate
change raised this to extinction level. Both these scenarios are relevant to aspects
of 21st-century anthropogenic climate change in that human activity has modified a
significant part of the modern global terrestrial landscape and that this, coupled with
21st-century climate change, is synergistically detrimental to many species as well
as local ecosystems and regional biomes.
Meanwhile, the human migration down North America to South America contin-
ued. One of the earliest major South American agricultural civilizations that depended
on a range of domesticated plants arose in Peru 5000-3800 years ago. The plants
used included cotton ( Gossypium barbadense ), squash ( Cucurbita spp.), chilli ( Cap-
sium spp.), beans ( Phaseolus vulgaris and Phaseolus lunatus ), lucuma ( Pouteria
lucuma ; formerly known as Lucuma obovata ), guava ( Psidium guajava ), pacay ( Inga
feuillei ), camote ( Ipomoea batatas ), avocado ( Persea americana ), maize ( Zea mays )
and achira ( Canna edulis ). This civilisation provided a foundation for many of the
features of subsequent Andean civilisations through to early historic times (Haas
et al., 2004; Perry et al., 2006). Other evidence suggests earlier American use of
some species.
Returning to Eurasia, once the climate had settled in the current Holocene inter-
glacial, the Neolithic agricultural revolution began to spread from the Near East
around 9000-5000 years ago (Hewitt, 2000). Agricultural practice grew and became
an increasing part of the landscape and helped the human population to expand.
Domestication of agricultural species did not always happen as a single event for
each species. For example, genetic evidence from Peter L. Morrell and Michael T.
Clegg from California University in 2007 suggests that barley ( Hordeum vulgare )
was domesticated more than once, once within the Fertile Crescent and a second
time 1500-3000 km further east. At Jeitun in southern Turkmenistan domesticated
forms of barley and einkorn wheat ( Triticum monococcum ) were being cultivated,
and domesticated goats and sheep were being herded, by 6000 , indicating a well-

developed agrarian society. Another example, from a team led by Jason P. Londo and
Yu-Chung Chiang in 2007, is that of rice ( Oryza spp.). Here, India and Indochina
may represent the ancestral centres of diversity for Oryza rufipogon . Additionally,
the data suggest that cultivated rice was domesticated at least twice from different O.
rufipogon populations and that the products of these two independent domestication
events are the two major rice varieties, Oryza sativa indica and Oryza sativa japon-
ica . Based on this geographical analysis, O. sativa indica was domesticated within

bc