Geoscience Reference
In-Depth Information
Both research teams looked at small, long-established, indigenous populations
(that are today dwindling fast and becoming diluted genetically). They both found
evidence that corroborates a common picture. A population containing some 600
women (possibly slightly fewer and maybe as many as 2000 or more) left East Africa
somewhere very roughly around 60 000 years ago or perhaps a little earlier. This was
in the middle of the last glacial but a good 30 000 years before the glacial maximum.
However, it was a cooler part of the glacial and although sea levels were not as
low as during the later glacial maximum it is possible (if not pragmatically likely)
that conditions were then favourable for migration across the Middle East. This
early colonising population appears to have taken a coastal 'express' route arriving in
southern Australia by 55 000-46 000 years ago (see below). This suggests a migration
speed of somewhere between 0.7 and 4 km/year and is of the same order of magnitude
as other genetically dated inland journeys of migrant species populations during the
last glacial.
It should be stressed, as discussed in Chapter 2, that (as with all dating tech-
niques) 14 C dating is prone to error. In the case of 14 C dating some error comes
from the rate of 14 C production in the atmosphere not being constant (it varies with
solar activity) and variations in the Earth's magnetic field. Other error stems from
sample contamination by more recent carbon (say through carbon carried by percol-
ating water), which affects potential sample 12 C: 14 C ratios. This particularly affects
the dating of older samples (with the least 14 C). For example, if a 40 000-year-old
sample was contaminated by just 1% with modern carbon then the dating error
would be around 7000 years. With regards to the dating of human remains there
have been two recent innovations. In 2004 a technique was developed for extract-
ing collagen (a family of fibrous proteins found throughout vertebrates) from within
bone, so helping to eliminate contamination. Second, since 1988 there has been a
continually improved understanding of variations in 14 C production over the past
50 000 years. Although this does not substantially affect the picture portrayed here, it
has been argued that modern humans migrated through Europe faster than had been
thought, and that their period of co-existence with Neanderthals was shorter (Mellars,
2006).
Early humans, and allied hominids, were hunter-gatherers. The remains of plant
grinders or pounders (such as grinding slabs, mortars and pestles) make their first
appearance in the Upper Palaeolithic from 45 000 years ago and suggest simple
food processing. The beginning of baking was an important step in human nutri-
tion, facilitating carbohydrate entering the bloodstream and being metabolised to
glucose. While such evidence is compelling, there are only a few examples where
food remains have survived to permit identification in association with such pre-
paratory artefacts. (After all, pestles and mortars could be used to make dyes, not
food.) The earliest direct evidence of simply processed food remains comes from
Galilee about 23 000 years ago with remains of wild barley ( Hordeum spontaneum )
and emmer wheat ( Triticum dicoccoides ). This was close to the LGM and the plant
species were wild. Domestication of wheat and barely subsequently took place around
10 000-9000 years ago, during the beginning of our Holocene interglacial. It there-
fore appears that a series of key developments in human food security took place
under different climatic conditions and across glacial-interglacial change. (We will
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