brad brace

3/3/2006

africa note2

Filed under: kenya — admin @ 6:51 am

Created 01/27/2006 2:15 am

almost always seven vertebrae in the neck
Pangaea

The processes which created the configuration of the continents
and the prevailing terrestrial landscape are exceptionally well
demonstrated in Africa, where the particularities of ancient
geology have endowed the continent wit immense deposits of mineral
wealth — Some of the earliest-known forms of life have been found
in Africa, and its ancient rocks are the repository of evidence
from all stages in the evolution of life forms. Africa was the
‘keystone’ from which tectonic forces drove the other continents
on their global wanderings. Dinosaurs and the earliest known
mammals were present on the continent 200 million years ago. — A
landscape of tropical rainforest and meandering rivers that
existed 40 million years ago in what is today the Sahara region of
western Egypt was the cradle of the primates from whom the human
line evolved. Tropical rainforests preserve the greatest plant
diversity on Earth, but they never have been permanent
fixtures–their extent and location varies with climatic change.
— Climatic change undoubtedly has a major effect on the
distribution and population size of all living species, but
evidence from Africa indicates that competition for resources has
had more influence than climate on the origin and evolution of
species. — The upright bipedal gait of humans is a unique and
highly inefficient mode of locomotion, but the anatomy of modern
apes, with 60 per cent of their body weight carried on the
hind legs, indicates that the common ancestor of apes and humans
was pre-adapted to bipedalism. Environmental circumstances in
Africa provide an explanation of why and how the fully upright
stance and bipedal gait evolved in humans. — The ancestors of
modern humans were bipedal nomads and scavengers who discovered
that sharp stone flakes were more efficient than teeth at
detaching meat from a carcass. Tools were teeth in the hand.

— The demands of stone-tool manufacture were significant among
the aspects of early hominid life which stimulated the development
of cognitive abilities and the evolution of anatomically modern
humans–homo sapiens sapiens–in Africa. — Thermoregulation and
access to water were crucial determinants of human survival in the
African cradle-land–and important preconditions for the evolution
of the species’ highly developed brain and social behavior. —
Genetic, palaeontological and linguistic evidence indicates that
anatomically modern humans existed only in Africa until about
100,000 years ago, when some migrated from the continent and
progressively populated the entire globe. — …a greater
time-depth of mutation was preserved among people in Africa, while
everyone else shared a predominance of mutations which had
accumulated in the relatively recent past. Setting these measures
of difference against the calculations of the rate at which
mutations occur, the geneticists concluded that the entire
population of the modern world was descended from a relatively
small group of people that left Africa about 100,000 years ago.
Extrapolating still further they from the present into the past,
they claimed that the distinctive form of modern humans had
evolved between 140,000 and 290,000 years ago in Africa… —
African environments demonstrate the universal relationship that
exists between soils, rainfall and vegetation in a natural
environment, and the extent to which biological adaptations enable
animals to take advantage of what is available. —

Though the fossil record of human evolution in Africa is unique
and extensive, it is also tantalizingly incomplete. Crucial stages
are still a matter of speculation. — Edit | Delete | Back to
Notepad

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