Scientific Methods

Thursday, April 06, 2006

Power point Abstract: Elizabeth van der Merwe

The Laetoli Footprints (ppt)


Elizabeth van der Merwe

2538521, University of the Western Cape, Bellville, South Africa




It is amazing that important information does not always appear in the expected way, but somehow has a way of appearing suddenly in the most unusual ways as the evidence of early bipedalism that was not confirmed from early fossil bones, but from an unusual fossil type namely homonid footprints preserved in volcanic ash (Tattersall, 1995). The footprints are so unique because in it behavior itself was conserved and behavior is one of the aspects that normally have to be inferred from fossil bones (Tattersall, 1995).


The footprints found at the Laetoli site represents the oldest evidence of hominoid  presence, which date back between 3,5 and 3,7 million years ago (Johanson et al. 1990; Lewin et al. 2004; Tattersall, 1995). One of the most important aspects explained in this presentation is the profound conditions that led to the preservation of the footprints in such perfect order. This includes the interaction between chemical and physical aspects of nature to preserve history.


Discoveries like this does not happen overnight, it includes a lot of insight, persuasive powers, arguments and conflict situations, perseverance, patience, precision, accuracy and finally a lot of very hard physical labor. Like the saying goes: “ the more people, the more different views” and in this case it is definitely applicable, because scientists like Mary Leakey, Louise Robbins, Tim White, Ron Clarke, Jack Stern, Randy Susman, Yvette Deloison, etc. all had their own interpretation of who were the owners of the homonid Laetoli footprints.


An important question is: Why is this obvious display of bipedalism so important? The answer lie in that bipedalism is considered as a modern human feature and has surpassed the animal quadruped features. Then after all, what happens now after the prints were exposed? How will it be preserved and who are now responsible for the conservation and maintenance of conservation?


The Laetoli footprints are also considered by some as the most spectacular archaeological discovery of the century (Leaky, 1981). The footprints have conserved for us a portrait of a few moments in the lives of some of our possible ancestors (Leaky, 1981).




Johanson  D,  Shreeve  J  (1990) Lucy’s child – The discovery of a human ancestor.

       Early Man Publishing Inc. Great Britain, pp 25-284.


Leaky RE  (1981)  The making of Mankind. Dai Nippon Printing Company Limited,

       Japan,  pp 40-70.


Lewin  R,  Foley  RA  (2004)  Principles of Human Evolution. Blackwell Science Ltd.  

       United Kingdom, pp 235-263.


Tattersall  I  (1995)  The last Neanderthal – The Rise, Success and Mysterious

       Extinction of our closest Human Relatives. Nevraumont Publishing Company,

       New York,  pp 39-40


Elizabeth van der Merwe
BCB Department
University of Western Cape


In order to discuss this fundamental question, we need to clarify some
basic concepts that pertain to evolution in general. Evolution depends
on individual genetic variability. However, the main selective force
that drives evolution in a specific direction is natural selection.
Darwin described natural selection as "the great battle of life".
Hereditary traits that lead to a survival advantage in a particular
situation along with differential reproductive success is evolution.
Without differential reproductive success, the advantageous genes of the
fittest individuals mean nothing, as they do not influence the gene pool
of a specific population. Another key ingredient of evolution is
isolation, as the influence of a successful individual's genetic
contribution is far more pronounced in an isolated population with a
relatively small genetic pool.

We can now investigate the various elements in more detail and apply it
to the modern human. The main mechanisms that generate genetic
variability (genetic mutation and genetic exchange) remain intact.
However, the real question is whether natural selection is still
operational as a selective force. Is modern life still enough of a
battle, with a sufficient number of casualties along the way, for it to
act as a strong selective force? Our large brain and dextrous behaviour
has allowed us to overcome most of the environmental challenges faced by
our ancestors, by artificial manipulation. Modern agricultural
practices have ensured levels of food security that were previously
unknown. Modern humans build houses and manufacture clothes that keep
them warm, even in some of the most hostile environments on earth.
Modern medicine has led to a drastic reduction in early deaths and the
lifespan of the average person in the developed world extends far beyond
the reproductive period. The unprecedented population explosion
witnessed during the past century demonstrates how the major driving
force of evolution, "the battle of life" has lost its bite.

In addition, individuals who are deemed to be most successful in
developed countries rarely have the most children. This indicates that
even if limited natural selection is still taking place, it does not
translate into differential reproductive success. Many factors
contribute to this, but two of the most important influences are
probably the practice of monogamy and the liberal use of artificial
birth control in the developed world. Globalization has also shrunk our
world to such an extent, that in practical terms we all share one
massive, and therefore static, gene pool.

Are humans still evolving? I think we can say with a fair amount of
certainty that the selective forces required for evolution to occur,
have been eroded in the modern developed world. However, this does not
imply that evolution is non-existent. In fact, the basic evolutionary
mechanisms are still in place and it only requires a strong selective
force, like a worldwide outbreak of bird flu, for evolution to awaken
from its present slumber.

Karen Marais
BCB Hons NISL student
University of the Western Cape
Private Bag X17