HAPPY ANNIVERSARY LUCY!
On November 24th, 1974, as dusk settled upon the southern
edge of the Afar Triangle near a village called Hadar, a team of scientists
organized by Yves Coppens, Maurice Taieb and Donald Johanson toasted a
tremendous discovery. They had been scouring this region for weeks--an area
Taieb had brought to the forefront of anthropological research years
earlier--and that morning their search paid enormous dividends with the find of
Dr. Johanson and his student Tom Gray. The skeletal fragments unearthed in the
Ethiopian landscape made up the most complete example of Australopithecus
afarensis ever found.
While they celebrated, a small tape recorder blared ”Lucy in
the Sky With Diamonds”, again and again. And then it struck someone--what finer
name than Lucy for the incredible specimen pulled from the sand that day?
In the coming months and years, this find would upend our
understanding of bipedalism, and rewrite a significant chapter in the story of
human evolution.
THE EMERGENCE OF HUMANS
The narratives of human evolution
are oft-told and highly contentious. There are major disagreements in the field
about whether human evolution is more like a branching tree or a crooked stick,
depending partly on how many species one recognizes. Interpretations of almost
every new find will be sure to find opposition among other experts. Disputes
often center on diet and habitat, and whether a given animal could walk
bipedally or was fully upright. What can we really tell about human evolution
from our current understanding of the phylogenetic relations of hominids
To begin with, let's take a step
back. Although the evolution of hominid features is sometimes put in the
framework of "apes vs. humans," the fact is that humans are apes,
just as they are primates and mammals. A glance at the evogram shows why. The
other apes — chimp, bonobo, gorilla, orangutan, gibbon — would not form a
natural, monophyletic group (i.e., a group that includes all the descendants of
a common ancestor) — if humans were excluded. Humans share many traits with
other apes, and those other "apes" (i.e., non-human apes) don't have
unique features that set them apart from humans. Humans have some features that
are uniquely our own, but so do gorillas, chimps, and the rest.
Virtually all systematists and
taxonomists agree that we should only give names to monophyletic groups.
However, this evogram shows that this guideline is not always followed.
Did the common ancestor of humans
and chimps conform to the ape-man myth and live in the trees, swinging from
vines? To answer this, we have to focus not only on anatomy but on behavior,
and we have to do it in a phylogenetic context. Apes such as the gibbon and
orangutan, which are more distantly related to humans, are largely arboreal
(i.e., tree-living). The more closely related apes such as the gorilla and
chimps are relatively terrestrial, although they can still climb trees. The
feet of the first hominids have a considerable opposition of the big toe to the
others but relatively flat feet, as arboreal apes generally do. But other
features of their skeleton, such as the position of the foramen magnum
underneath the skull, the vertically shortened and laterally flaring hips, and
the larger head of the femur, suggest that they were not just mainly
terrestrial but habitually bipedal, unlike their knuckle-walking relatives.
Most evidence suggests that the hominid lineage retained some of the anatomical
features related to arboreal life and quadrupedal gait even after it had
evolved a more terrestrial lifestyle and a bipedal gait. There is no fossil
record of these behaviors, but the balance of the available evidence supports
the hypothesis that the hominid ancestor was terrestrial and bipedal.
Much discussion in human
paleontology surrounds the evolution of a bipedal, upright stance. When and why
did this occur? One thing to keep in mind is that "bipedal" and
"upright" are not equivalent terms. An animal can be bipedal without
having a vertical backbone (think T. rex). It seems clear from the fossil
record of hominids that habitual bipedality preceded the evolution of a
recurved spine and upright stance. Other changes in the gait, such as how the
relatively "splayed" gait of chimps evolved into the gait of humans,
who put one foot directly in front of the other, involve studying the hip
joint, the femur, and the foot.
We do know that by the time the
animals known as Homo evolved, they could make tools, and their hands were well
suited for complex manipulations. These features were eventually accompanied by
the reduction of the lower face, particularly the jaws and teeth, the recession
of the brow, the enlargement of the brain, the evolution of a more erect
posture, and the evolution of a limb more adapted for extended walking and
running (along with the loss of arboreally oriented features). The evogram
shows the hypothesized order of acquisition of these traits. Yet each of the
Homo species was unique in its own way, so human evolution should not be seen
as a simple linear progression of improvement toward our own present-day form.
Read more at: http://evolution.berkeley.edu/evolibrary/article/evograms_07
Read more at: http://evolution.berkeley.edu/evolibrary/article/evograms_07
IS HUMAN BEHAVIOUR GENETICALLY OR CULTURALLY DETERMINED?
From our point of view the human
behaviour is controlled by both genetically and culturally facts. Behaviors
distinguish human beings from other creatures and from each other, so as in
http://www.encyclopedia.com/topic/Behavioral_genetics.aspx appears, some genes
influence the way individuals select and shape experiences and other genes can
affect an individual's susceptibility to these experiences.
On the other hand and in our
opinion, an individual's genome may set boundaries on various traits and potential,
but it cannot determine how we will organize our life. So genes are not enough.
Humans cannot survive without culture. Everything we see, touch, interact with
and think about is cultural. It is not written in our genes to know talking in
mother tongue and we could not survive winters without protective clothing,
which are provided culturally. We could not obtain food without being taught
how.
But genetically speaking, if the
entire human genome is sequenced, why those behavioral genes are unknown? The
answer is not clear but it seems that human behavior is in fact and interaction
between genetics and culture.
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