Anatomical Evolution of Man

QIP CD Cell Project IIT Guwahati 2009-10

• There was a rapid increase in size of brain during the various evolutionary stages

• The rapid increase in cerebral volume was concentrated mainly in the association cortex (dealing with complex calculations), hippocampus (dealing with memory) and cerebellum (dealing with posture and balance).


• Another significant change was a second expansion of the brain and the descent of the larynx in the wind pipe.

• An important event was the evolution of laryngeal nerves which connects the brain to the larynx and allows us to speak. This feature is also found in some reptiles and amphibians.QIP CD Cell Project IIT Guwahati 2009-10

• One of the main differences between the apes and our ancestors was that the memory of apes was episodic.

•While our ancestors, on the other hand, could retrieve their memories as and when they wanted.

•This meant that our ancestors had access to wide repertoire of memories which allowed them to remember the body representations of various activities and hence in turn allowing them to perfect them and even improvise on them.


• As the whole body became a tool for communication new social territories began opening up: complex games, extended competition, pedagogy through direct imitation, a more complex repertoire of facial expressions and intentional group displays of aggression, solidarity, joy, fear and sorrow forming the basis of the first hominid cultures.


• The social, cultural, anatomical changes surrounding the hominids paved the way for lexicon invention.

• The language was an offshoot of the lexicon invention which enabled our ancestors to enable relationship between words and the imposition of metalinguistic skills the govern the uses of these words


• Language gradually assumed a dominant and an important role the human culture but never eliminating the mimetic skills learned earlier on.


• This resulted in the well known phrase “survival of the fittest”, where the organisms most suited to their environment had more chance of survival if the species falls upon hard times.

• Those organisms who are better suited to their environment exhibit desirable characteristics, which is a consequence of their genome being more suitable to begin with.


ANATOMICAL IMPLICATIONS OF DARWIN’S THEORY

Right Handedness BipedalismQIP CD Cell Project IIT Guwahati 2009-10

RIGHT HAND SPECIFICITY IN HIGHER HOMINIDS

Handedness is an attribute of human beings defined by their unequal distribution of fine motor skill between the left and right hands


HANDEDNESS

Most humans (say 70 percent to 95 percent) are right-handed, a minority (say 5 percent to 30 percent) are left-handed, This appears to be universally true for all human populations anywhere in the world. There is evidence for genetic influence for handedness although it can be influenced (and changed) by social and cultural mechanisms.

- It is not unusual for individual animals to show a preferential use of one hand over the other, to develop an individual hand preference. But there is no consensus among researchers that any non-human species shows the same species-level handedness found in humans.


HANDEDNESS

What is the cause of handedness and why the handedness is majorly dominant in humans and Not animals as such…?


Experiment • US university scientists were able to synthesize a drug that could generate similar environment that existed in the times when major anatomical transformations were occuring among previous hominids .

•When this drug was administered to apes it was found that those showed greater endurance to that drug that had greater right hand specificity.

• Thus experiment revealed that right handedness gradually grew during the phase of evolution of prehominids into later developed hominids representing this property grew as a result of cultural and anatomical human development which is now visible in existence of species level handedness in humans


ORIGIN OF BIPEDALISM

As the successive homonids generations were advancing in cultural and neural fields it demanded more efficient energy management, therefore bipedalism was one the most significant anatomical transformations of the era. QIP CD Cell Project IIT Guwahati 2009-10

• Anthropologists theorized that early humans began walking on two legs as a way to reduce locomotor energy costs.

• To examine this theory among humans and adult chimpanzees, researchers have found that human walking is around 75 percent less costly, in terms of energy and caloric expenditure, than quadrupedal knucklewalking in chimpanzees.

• That energy savings could have provided early hominids with an evolutionary advantage over other apes by reducing the cost of foraging for food.


•The thermoregulatory model (Wheeler Labs) views the increased heat loss, increased cooling, reduced heat gain and reduced water requirements conferred by a bipedal stance in a hot, tropical climate as the selective pressure leading to bipedalism.

• Sleeping on back is possible anatomically only in bipedals and research shows sleeping on back is least expensive way as far as energy is concerned.


CULTURAL DEVELOPMENT AND

INHERITANCE over the period of evolution,the humans which were once a mere food gatherers and hunters have evolved not only anatomically but also culturally as well as technologically.This vast sea of knowledge which has been accumulated over the period of time is not just a 1 generation process but gradually developed as the fruits of inheritance.


INHERITANCE• This property of passing on valued knowledge as well as skills to the successors called inheritance which has ultimately played important role in the development of human culture as we see today.

• As humans developed anatomically majorly in the neural area, the basic human efforts became more and more thoughtful as the thinking processes had begun

• The era of language development dawned upon and soon man was making long strides in the cultural expansion and knowledge.


• Humans started resorting to external memories to better organise the complex structure of their lives which is evident in the large number engravings ,ancient texts, and sculptures. • This era marked not only the acquisition of knowledge but also their preservation which could be rightfully transferrred to next generations which further developed and consolidated them .
