WHAT COULD WE LEARN FROM THIS CRETACEOUS – TERTIARY EXTINCTION EVENT ?
MAN’S FUTURE – EVOLUTION OR EXTINCTION ?
Like all other living creatures of this planet Earth, man is a mortal being. Whosoever had arrived on this planet must also depart. As a biological species, what are man’s chances of survival in the future ?
COULD MAN EVOLVE INTO A NEW SPECIES ?
Man is a member of the order of Primates, which is a part of the class Mammalia. Modern humans belong to the species Homo sapiens. Man is the only species in the genus HOMO of the family Hominidae that is living today. All other ancestral forms of the genus HOMO are extinct. The early Homo sapiens was possibly present in southeastern Europe 350,000 years ago. The numbers and range of humans has increased about 100,000 years ago. The rate of expansion of human population is related to technological advancements that increase the availability of food, or of major medical advances that reduce the number of deaths. Man not only fully inhabits and utilizes a wide range of environments but also alters these environments to his own ends. With a variety of sophisticated technologies interposed between man and the natural environment, the environment cannot exert pressures on the human species in the same way that it has on other species.
Essentially, the modern synthetic view of evolution could be defined as a change in gene frequency. Evolution could be described as change in the genetic composition of a population through time. For purposes of speciation or separation into new species, we need to demonstrate cumulative and important changes in the population gene pool. In the last 250,000 years there is no evidence to show any important changes in the population gene pool. Practically speaking, man’s evolution into a new species is arrested because of the intervention of culture between man and his environment.
THE BIOLOGICAL PHENOMENON OF EXTINCTION
In biology, extinction refers to the dying out or termination of a race or species of animals or plants. Extinction occurs when a species can no longer reproduce at replacement levels and all the surviving members perish at the end of their life spans which could be shortened by harsh environmental stresses. The causes of extinction include the following: 1. extra -terrestrial, 2. geological-climatical, and 3. biological. Most extinctions are thought to have resulted from environmental changes. A species could be affected in either of two ways :
1. The doomed species is not able to adapt to the changed environment and would totally perish without descendants;
2. The doomed species may adapt but, in the process, may evolve into a distinctly new species. When this transformation is completed, the doomed species would be identified as an extinct species. It should be noted that this kind of transformation of one species into a new distinct species is not actually observed by any person. The chances of man evolving into a new species is less likely because man has to some extent arrested this process due to the development of his abilities to manipulate nature.
Extinction is an ongoing feature of the Earth’s flora and fauna. The fossil record has served to demonstrate the history of most major groups of animals and plants. The record indicates the occurrence of fairly sudden extinctions of certain groups at certain times, and the fossil record also reveals the occurrence of a number of mass extinctions each involving the demise of vast number of species. A typical species becomes extinct within 10 million years of its first appearance and only one in a thousand species that have existed remain today. Some 99.9 percent of all species that have ever lived on Earth are now extinct. Mass extinctions are ecological disasters but they may also create opportunities by removing once dominant groups.
CRETACEOUS-TERTIARY EXTINCTION EVENT( K-T EVENT)
A drastic example of extinctions is provided by the dinosaurs. About 65 million years ago, at the end of the Cretaceous period all the major groups of dinosaurs and several forms of marine life became extinct more or less simultaneously. It has great significance because it ended the reign of the dinosaurs and opened the way for mammals to become the dominant land vertebrates. Some biologists conclude that humans owe our present dominance because of this K-T Event that saw the end of the dinosaurs.
Evidence points to the impact of an asteroid hitting the Earth as the cause of this extinction. An important aspect of such impacts by heavenly objects would be the creation of tremendous amounts of ionizing radiation which has played a devastating role in wiping out the marine life. It is suspected that catastrophic events such as an asteroid impact/radiation may have triggered other mass extinctions as well. In fact, mass extinctions appear to have taken place approximately every 26 million years. Some paleontologists proposed that a cyclical cosmic event cause these periodic die-offs.
THE LESSONS FROM DINOSAUR EXTINCTION
The history of dinosaurs upon planet Earth clearly tells us and warns us about the vulnerability of human existence. The structural differentiation and the sophisticated functional organization of man makes him a very complex organism. Such complexity actually places man in a position of disadvantage when a cataclysmic cosmic event actually happens. Organisms that are structurally simple and functionally primitive and those that feed upon dying or decaying organic matter may survive better and ride over the chaos caused by a massive collision.
The theory of evolution would not be able to offer a sense of hope to humanity and just like the dinosaurs, man would be the next doomed species. Life forms have become extinct and yet life continued. A living thing is a composite of form, and substance. We tend to pay attention to the form and disregard the nature of the substance. The living matter or substance has endured all extinction events over period of 3.5 billion years after the first appearance of Life on planet Earth. This living substance survives and displays the quality or the characteristic of being imperishable, immutable, immovable, and eternal. There is hope that the living substance would again survive a future major extinction event. What about the life form that we recognize as man? Man could derive some comfort from the Book of Genesis, chapter 8, verse 22 which promises:
“As long as the earth endures,
seed-time and harvest,
cold and heat,
summer and winter,
day and night
will never cease.”
Dr. R. Rudra Narasimham, B.Sc., M.B.B.S.,
Kurnool Medical College, Kurnool, Andhra Pradesh, India,
M.B.B.S. Class of April, 1970.