Picture source: http://imgarcade.com/1/evolution-of-man/
Humans
have evolved over approximately 15-20 million years ago (MA) within the Hominoidea
family. Homo sapiens made their appearance towards the end of the Miocene epoch
(geological time) around 8 MA within eastern Africa. They are known to be descendants
of Chimpanzees and Gorillas. About 3 MA a saw the closing of the Panama Seaway,
which appeared with major changes with Earth’s atmosphere and biosphere.
Greenland’s ice sheet extended to continental cover showing drops in
temperature, changes of surrounding vegetation and an interruption in mass
water exchange between the Atlantic and the Pacific Ocean, which was a leading
factor to the diversity of marine life on both sides of the land bridge. This
also saw mammals on land colonise a subcontinent.
During
the time of the Panama Sea way closing there was an increase in salinity
between Atlantic and the Pacific Ocean. This is because the freshwater between
the two was eliminated casing the amalgamation of the oceans. Increase in
temperatures saw the expansion of Savanna and warm-temperate forest in both
Australia and Africa. This expansion could have been a trigger in the movement
of animals going from treetops to the ground and causing bipedalism, as food
many have moved form high area to a low area. Bipedalism is a game changer it
saw the transition from apes to Homo sapiens. Advantages such as being very tall ensured that they were able to see
over grasses to see forthcoming predators, locate food and shelter. Having
free hands to carry food, weapons and babies. Major changes seen in fossils, similarities
are seen in the mid-Miocene. Dryopithecine and proconsulid apes had differences
such as changes in the elbow structure and elongation of forearms is like those
of hominid decent and is similar to apes respectively. Later date fossils show
changes in pelvis area from long and wide to support the large leg muscle
attachments, whereas the short and wider pelvis region for Homo sapiens enabled
the support of internal muscles that are used in the leg to walk and to reduce
the stress of internal organ weight on the hips, and for woman to accommodate
the process of child birth. These changes came about from original tectonics
moving causing changes in environments and climates forcing animals to adapted
to survive and reproduce.
Picture Source:https://aspergerhuman.wordpress.com/tag/orangutan/
Adaptations
seen with the skeletal frames of both Homo sapiens and apes show how we as a
species have evolved and adapted to our changing surroundings to survive. Apes
presented with larger muscles within the skull to support the mechanics of jaws
movements for chewing in particular tough plant material, as well as sutures on
top of the skull. This compared to Homo sapiens who have a larger more rounded
cranium and compared apes where the mandible bones is not as strong. Increased
strength within the jaw possibly came form the increased availability of plants
for food and therefore needed a great deal of power to chew through it as well
as meat. Spinal changes can also be observed, apes show a C-shaped spine that
which counterbalances the downwards force of the chest and organs, homo sapiens
show having an S-shaped spine this allows them to stand upright as the body weight
is kept above the hips (used as shock absorbers). The rib cage is flattened
front to back to keep the body weight close to the spine and over the centre of
gravity, whereas the rib cage of an ape is flattened form the sides to be able
to accommodate for a bigger herbivore gut.
It
is thought that we can put these changes over time to the change in climate
within eastern Africa as well as the changes within their environment that was
a major trigger for bipedalism, the change from trees to ground, from here
everything developed, legs, hips, skulls showed extensive growth and
development. The increase ice coverage forced the movement of animals to readapt
within their new home. For this example can we conclude that with the evidence
shown to us that tectonics played a larger part within this area of diversity
of mammals on Earth?
Picture Source: https://blogs.otago.ac.nz/ouassa/category/resources/biology-resources/human-evolution/
Rosie Hebden
Reference:
Burrows, C. J., McCaw, A., &
Leonard, L. (1994). Genesis: A model for the origin of the first hominids.
Christchurch, N.Z: Rebus Publications.
UCMP (University of California Museum of
Paleontology). (2011). The Miocene Epoch.
Retrieved 15/09/2015 from
http://www.ucmp.berkeley.edu/tertiary/miocene.php
Schmittner, A., Sarnthein, M., Klnkel,
H., Bartoli, G., Bickert, T., Crucifix, M.. . Zuvela, M. (2004). Global impact
of the panamanian seaway closure. Eos, 85(49), 526.
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