By: Helmi Junaidi
This topic is still frequently debated by evolutionists,
between supporters of gradualism and punctuated equilibria. The latter theory
was proposed by Stephen Jay Gould, paleontologist from Harvard University and
Niles Eldredge of Columbia University. One of the main subjects of debate
between supporters of gradualism and punctuated equilibria is the existence of
an organism or a fossil that relatively statis (but in fact they changed as
well) for a long period and then suddenly changed in a relatively short period.
The word "short" here is measured in geologic time scale, and this is
not only one or two thousand years, but at least some ten thousands years.
There are some species that change only slightly and refered to as living fossils
such as horseshoe crab, tuataras and coelacanth. Coelacanth is still found
in the East Africa Sea and around the island of Madagascar. In 1998 it also
found in the sea South of Sulawesi.
Actually, most species didn’t changes abruptly, but they
changed slowly and radiated to produce many varieties of new species. Perhaps there were two kind of evolutionary process, but the “statis” species actually changed
as well, not really in stasis condition. Only relatively statis. Regarding
coelacanth, tuataras and some other living fossils, their relative stability
are probably due to physical condition of these organisms that are relatively
flexible and can adapt easily with ever-changing environmental conditions.
While other organisms underwent much change, they needed little physical changes
to adapt.
Such phenomenon because changes in the organism is not
"mandatory", but depends on the environment where organism lived. We
know that climate and environmental conditions on earth vary widely. The
species that studied by scientists who argue that evolution took place suddenly
perhaps because they studied species that lived in a relatively stable
environment. But, this phenomenon is not applicable to all species, only to
some particular species. Those species didn’t need to change because their
environment had not much changed. If they changed they could become
extinct because they no longer fit to their environment. After a relatively
stable period, the climate changed drastically and caused significant changes
in many species. But we know that not all species inhabite statis environments,
they inhabite various places and most places on earth are constantly
changing. As such, they do not have the chance to have stability. It seems that punctuated
equilibria is just a special phenomenon for particular species which lived in
particular environment. But keep in mind that they were not really in statis condition (equilibrium), but changed as well because all places on earth
constantly change, both major and small changes. Not really an equilibrium. All
living things, including humans, evolve continuously in every generation.
If punctuated equilibria is indeed true, obviously it
ocurred only to some particular species at particular places and it cannot
explain the evolutionary process of all living things. This theory
will find difficulty to explain evolutionary process of most living things,
including human, for example the existence of transitional fossils of hominids
which half Homo erectus and Homo sapiens or half Homo erectus and half Homo neandertalensis.
The fossil evidence for the few hundred thousand years leading up to the time of the Neandertals shows a gradual change from a Homo erectus form to one approaching the Neandertals. Particularly in western Europe, the evidence shows a gradual decrease in the size and frequency of the anatomic characteristics of H. erectus and a gradual increase in features suggestive of the Neandertals. From this a gradual emergence of the Neandertals from earlier regional populations of archaic humans can be inferred, especially in western Europe and probably across their entire geographic range.The changes between Neandertal ancestors and the Neandertals highlight their characteristics. Brain size gradually increased to reach modern human volumes relative to body mass, even if Neandertal brains and braincases tended to be somewhat longer and lower than those of modern humans. Neandertal faces remained large and especially long, similar to those of their ancestors and retaining browridges, a projecting dentition and nose, and the absence of a full chin. Their premolars and molars were reduced to the size of early modern humans, and their chewing muscles and cheek regions were reduced accordingly; yet their incisors and canines remained large, like those of their ancestors, indicating continued use as a vise or third hand. (Neandertal Origins and Anatomy, Encyclopedia Britannica)
Now it is obvious
that human evolution, and also other species, occured
gradually. Not suddenly. In addition, punctuated equilibria will find
difficulty to explain the overlap in human ancestors, when older
species coexisted with newer species. This is a very strong evidence that evolution did
not jump from one species to another, not in a sudden burst. Many older
species coexisted with newer species for some ten or even hundred thousand years. And certainly they would compete for
"lebensraum" and sources of food. There might be interbreeding
between the two species or the absorption of defeated species. So, although a
certain species was extinct, their genes still survive in many individuals in the
next generation.
James Hutton said that the present is the key to the past.
The forces that were responsible for shaping the geological features of the
earth in the past are identical to those that are operating in modern times. He
said that there had been time enough for such features, however tremendous, to have
been formed by the gradual processes--such as erosion and sedimentary
deposition. And those processes are still operating right now. This became a fundamental
aspect of modern geology and also demonstrated that the Earth was billions of
years older than the strict biblical notion of 6,000 years.
I think we can apply uniformitarianism to evolutionary
process as well because the same process occured in human ancestors. And
certainly a process that will shape our future, too. The most obvious example
because it is well-documented, is in the history of Europe and Mediterranean
region where human races from different regions compete, conquered each other
and absorbed each other, sometimes formed new races if the number was
relatively balanced. For example we can see the disappearance of the Sumerians.
Their race and culture were completely disappeared, but their gene certainly
remain in the Semitic peoples who conquered them. Sumerians gene still exist in
many modern Iraqi people. Or we can see the fate of Carthage. The Phunisians
had disappeared as a nation, but their gene still exist, including in many Italians since after the destruction of Carthage hundreds of thousands of its
residents brought to Rome as slaves. Another example, the ancient Egyptian
population absorpsed into Muslim Arabs. In European history we can see the fate
of the Picta, Celts, Huns, Avars, Goths, Vandals, Lombards etc. Their race and
culture had long been extinct, absorbed by the people who conquered them, but
it doesn’t mean that their gene extinct. Their genes still survive until modern
times. Uniformitarianism James Hutton indeed applies in evolutionary theory as
well, and not only in geology. The present is the key to the past. The
following excerpt can confirm it.
Certainly, H. sapiens did not spring fully formed from their H. erectus ancestors but, through the process of mosaic evolution, crossed the sapient threshold at varying times in the development of different functional complexes. The resultant combination of H. erectus and H. sapiens features is well demonstrated in a number of specimens, notably Omo II, Steinheim, and Vértesszollos. (Man's continuing evolution, Encyclopædia Britannica, Inc.)
After isolation and the formation of new races, when they
met and intermarriage was still possible, there would be absorption by the
stronger but when intermarriage no longer possible because the isolation lasted
too long there was annihilation. However, if we see that some modern human chin
are not fully developed or even chinless, which shows the characteristics of
archaic species, it is quite possible that archaic gene still survive until
modern times. If we look at human faces in Southeast Asia, including in
Indonesia, we often find humans that have no chin, or their chin not fully
developed. When I was still in college my friends sometimes make droll comments
when they saw chin strap on helmets and said that some Indonesians don’t need
it because they don’t have chin. Ancient human gene indeed is still present
among modern humans today.
It seems that punctuated equilibria now difficult to
be defended because human beings and most other living things evolve gradually.
Even some species of hominid coexisted or overlapped with other hominids, for
example H. erectus coexisted with H. sapiens and H. Neandertal coexisted with H. sapiens. They
did not jump from one species to another. Even archaic hominid gene still
present among modern humans today. In any of you, in any of us. Thus,
gradualism remain a plausible theory to explain the evolutionary process of all
living things.
Yogyakarta, Central-Java, 2002
