'Lucy' and The Arc of Visual Perception

Fossil Evidence

Looking at the overall picture the facts are that the numbers of fossil remains identifiable as hominid from the period prior to 4 million years ago are non-existent, and from this date up to 100,000 years ago, they are very rare. Most are incomplete fragments and no complete skeleton has been discovered to date.

The famous ‘Lucy’ remains consist of about 50 components most of which are fragments, representing about 37 bones, or numerically less than 20%, of the over 200 separate bones of a complete primate skeleton.

In contrast we have a much better idea of the skeletal structure of dinosaurs of 65,000,000 years ago than we do of our suggested ancestral line prior to 100,000 years ago.

This rarity of hominid examples is undoubtedly due mainly to the dispersal and destruction of remains by predators and scavengers before burial was practised in the last few tens of thousands of years.

The fossil evidence on which the theory of a fully erect A.Afarensis is effectively based is, to say the least, minimal. Some experts dispute that these fossils provide conclusive evidence that hominids at this time, and indeed that some subsequent species, were fully erect.

Therefore it can be stated that neither the ‘Lucy’ fossils on their own, nor any other A.Afarensis fossils, provide indisputable and unequivocal proof that this creature was fully erect in locomotion in the manner of man today.

The Laetoli Evidence

The Laetoli footprints combined with the separate and, save by assumption, unconnected ‘Lucy’ and other A.Afarensis fossils are generally considered as confirming that hominids were fully erect over three million years ago.

These footprints are indeed significant and the main arguments put forward in favour of these prints as indicating permanent upright stance are that they show evidence of an arch in the foot thus enabling the foot to exert leverage in walking, similar to the action of modern man. Also that the big toe is aligned closely with the others, rather than widely separated or prehensile as in gorillas and chimpanzees.

The prints were made in a deposit of volcanic ash, moistened by rain and preserved by the subsequent drying and hardening of the ash. They show a large creature walking by the side of a smaller and it is thought that another small member was following literally in the larger’s footsteps.

There may be many explanations for how these prints came to be made and the following is one interpretation based on an attempt to look at this situation from the practical point of view of the creatures at this time.

In the aftermath of a local volcanic eruption they are travelling, perhaps to escape the after effects of this eruption. They face a situation of a soft, possibly wet, new laid layer of ash and are forced to cross this to a safer position. This is an unknown and possibly dangerous crossing, as the ash could be deep in places, it may be slippery and perhaps it is still hot, it could also obscure sharp stones or other potentially injurious objects. All these things make this a traumatic and stressful situation and the traverse would not be attempted if there were an alternative route or option.

In these circumstances they abandon their normal independent mode of travel and move close to the large member for support and assistance. To be able to support the smaller one, or ones, the larger must hold on to them naturally by their front limbs. They feel their way with their feet, treading very carefully. The larger holds one hand out to the side and perhaps the other out to the rear for the one stepping in his tracks, which is of course a safer option than walking to one side and making its own. The fact that the rear smaller creature lengthens its stride to step in the larger’s footsteps is a further indication of stress.

With respect to the closed toe aspect of the prints, those who have walked barefoot in deep, soft, wet mud will be aware that the natural and unavoidably instinctive reaction to these conditions is to try and keep your toes tightly held together.

Also when walking on hot sandy beach the instinctive reaction is to place as little flesh as possible in contact with the hot material. The toes are tightly curled up close together and the foot canted to one side to try and keep the more sensitive inner part of the sole off of the sand.

Observation of Gorillas and Chimpanzees show that the normal positioning of the toes of the feet in both quadrupedal and bipedal locomotion is with the front toes extended and the prehensile toe extended to the side. However both are capable of clenching the toes of the foot into a ‘fist’ with the front toes from the first joint bent back under the sole of the foot and the prehensile big toe brought into alignment with them.

It is therefore a possibility that a primate of a similar species capable of bipedal motion could have made these prints in this manner.

This is of course speculation, however it is clear that while these prints may be evidence of bipedalism they, like the ‘Lucy’ fossils, cannot be considered as conclusive proof of a bipedal locomotion as upright as that practised by man today.

Conclusions

The fundamental questions about the evolution of man still remain unanswered. These are why did an arboreal ape become erect and how did this progression proceed.

If these questions are applied to the assumption that A.Afarensis had achieved this remarkable transition 3.5 million years ago then these questions, in the absence of any fossil or other evidence, remain not only unanswered but in all probability unanswerable.

However if these are asked on the basis that A.Afarensis was still in the transitional stage of becoming fully erect then a logical pattern appears.

Essentially the only remains that are indisputable indications of the mental development of pre-historic man are the rare skull components, the numerous stone and later bone tools, evidence of the use of fire at about 1.5 million years ago and later the construction of semi-permanent shelters from about 800,000 years ago.

The fossil records of hominid skulls from 3.5 million years ago show a progressive but slow increase in the capacity of the brain cavity. While all these examples are not necessarily of our direct line, if A.Afarensis was an ancestor the capacity of the cranium has increased by about 250% during this period.

If we measure the average rate of increase in volume from A.Afarensis to H.Habilis and further to H.Erectus we get a figure of 1ml increase every 4750 years and from H.Erectus, at about 1million years ago, to date we get a rate of 1ml every 2500 years.

This expansion of the cranium was combined with and concurrent with its change in shape and movement forward expanding the forehead upwards and forward over the eye sockets. At the same time in profile the projection of the jaw has receded considerably leaving the nasal extension effectively in place.

Stone tool making began about 2.5 million years ago preceded, it can only be assumed, by wooden implements and perhaps the use of naturally occurring materials such as sharp stone flakes or the shells of molluscs or crustaceans. However for over one million years from this point there is little evidence of any significant development or modification of the earliest dated examples and essentially the same type of stone tool was produced. At about 1.5 million years ago modifications and improvements then began to appear at an increasing rate. Different materials were used and there was a progressive development in the variety of tools and weapons produced, leading ultimately to the finely crafted axes, arrowheads, etc. of the latter part of the Stone Age.

The diagram below shows the curve of the progressive increase of cranial capacity of successive hominid specimens over the period in question. If a curve could be drawn of the progressive development of the types, the quality and the finish of tools and weapons over the same period then while this may not have precisely the same characteristics it would clearly show an approximately concurrent and exponential change.

As discussed earlier the progression from a chimp-like quadrupedal locomotion towards the fully erect would in the initial stages be very slow. As the posture became more and more erect and energy efficient, the result would be an ability to spend more time in a bipedal posture. The reduced expenditure of energy in locomotion would lead to increased endurance and consequently result in the possibility of a greater range of movement.

The rate of evolutionary progression to upright locomotion would accordingly tend to increase exponentially.

This suggests that a graph showing the progression from a quadrupedal to an upright locomotion would show similar exponential characteristics to that of the expansion of the cranium and that of the development of tool manufacture.

The inference is clear in that, in the absence of any conclusive evidence to the contrary, it is therefore logical to suggest that the progression to upright kept pace with the changes in the shape and dimensions of the skull. The movement forward of the brain cavity and the recession of the jaw, or in other words the realignment of the facial plane about the eye sockets, is accordingly an indication of the progressive change of the attitude of the upper spine to a near erect position in locomotion. This would suggest that this progression has been ongoing and only recently been ‘completed’ in the last one hundred thousand years.

This lends credence to the theory that the use and the carriage of food, tools and weapons was an incentive to use a bipedal locomotion and was therefore an influential factor in the evolutionary process.

However it would also answer the serious difficulties that arise from presenting A.Afarensis as being a fully erect, hunter/gatherer roaming the savannah at will in a family group within a larger social group or tribe in a manner not far removed from that of some so called 'primitive' tribes that still exist today.

The problem is that all this suggests intelligence, as well as good co-ordination, and begs the question of how this mental capability was achieved with a cranial capacity only slightly larger than that of a chimpanzee.

This then gives rise to the difficulty of explaining the subsequent threefold increase in cranial capacity in the period to date. This huge increase can hardly be explained either by the evident increase in manual dexterity or the beginnings of oral and later written language, or the concept of ‘self’, reason, abstract thought, etc.

The human brain is an inordinately expensive organ to maintain, representing just 3% of body weight and consuming over 20% of the energy resources of the body. As stated earlier, nature in the process of natural selection, does not waste resources in producing, and maintaining, a component that is not utilised.

It is clear therefore that the increase in cranial capacity simply kept pace with the increasing efficiency of the progressively more upright posture in motion. This improved efficiency leading to an increase in stamina or endurance, which in turn widened the range of potential movement from a home base. Better bipedal co-ordination would result in improved agility and speed over the ground and all these factors together with the need to process, store and access and react to an increasing amount of information more and more rapidly would result in an obvious need for an expanded mental capability. This progression would neatly coincide with the development of manual dexterity, oral communication, etc. and the combination of all these factors would clearly explain the observed exponential expansion of the brain.

This idea is also reinforced by, and can explain the enigma of the co-existence of the relatively primitive Neanderthal Man with Cro-Magnon Man during the last one hundred thousand years. The prominent jaw and other cranial features such as the prominent ridge of the forehead together with the round shouldered stance suggest that Neanderthal was still in the latter stages of evolving to an erect posture. Cro-Magnon man was at a more advanced stage and was more erect and its lighter structure indicates that it would be faster and more agile. This in turn would suggest that it was better co-ordinated and perhaps more dextrous in the use of weapons. In competition for the same food sources Cro-Magnon would have a distinct advantage. It would be like pitting a racehorse against a carthorse.

The possibility is that both evolved from the same original species and were somehow separated geographically. Environmental and other factors may have resulted in differing adaptations at different rates and when the two subspecies again came into contact through migration Cro-Magnon had evidently won the race to the more efficient erect posture and subsequently eliminated Neanderthal.

A.Afarensis cannot have been as erect in locomotion in the same manner as that of man today. Its mobility on the ground was limited, its bipedal co-ordination poor. Its diet was overwhelmingly vegetation. It inhabited the forest and did not venture willingly in to open country. Its level of intelligence was possibly more advanced than that of modern chimpanzees but not by much. A.Afarensis was still an ape.

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