Similarly, Lake Victoria in Zimbabwe is home to hundreds of species of cichlid fish, many of which are similar in most respects with the key exception of color pattern. Female cichlids use color pattern to identify mates of their own species, preventing them from mating with the wrong species. Because they exhibit this form of behavioral isolation, the many species of cichlid fish in the lake will not mate with one another, and their reproductive isolation remains fixed, generation after generation.
Natural selection, however, aside from the chance aspects of mutations, is not entirely a random process, but is instead predictable and is the core mover of establishing new forms and more complicated and successful forms and of design and order throughout nature from the sub-atomical to the macro-universe. Better adapted genotypes will tend to persist and to reproduce and to determine the direction and design of future generational development. The cumulative process of myriad small changes over time is directed by nonrandom survival and proceeds in the direction of increased complexity, specialization, and more successful function. Understanding the effect of natural selection was the paramount contribution of Charles Darwin to the world’s understanding of the process of evolution.
Darwin, however, was wrong about one aspect of evolution with regards to speciation. He admitted to confusion and ignorance about the process but presented the opinion that new species arose to fill empty niches in nature. A mass of research has established that–to the contrary–speciation occurs as an evolutionary accident. Species do not arise to increase diversity nor to provide balanced ecosystems. They are simply the result of genetic barriers that arise when spatially isolated populations evolve in separate directions. This is known formally as the theory of geographic speciation. This process is somewhat comparable to the establishment of different languages when populations with the same proto-language separate, then develop different linguistic language selections, then even more distinct language differences over time to the point that the languages are more than just dialects of the same language, but become mutually unintelligible. Consider the examples of sister tongues Latin→ Italian→ Spanish→ French or German→ English.
Diagram of mutation and selection in evolution. (Photo credit: Wikipedia)
The finding of naturally occurring separated species arising from the same ancestor is a requirement of verification of the theory of geographic speciation. A dramatic example exists in the case of Panamanian snapping shrimp. Each side of the Isthmus of Panama harbors seven species of the shrimp in shallow waters. The remarkable thing about these seven species is that the closest genetic relative of each species is its counterpart on the opposite side of the isthmus—Atlantic and Pacific Ocean snappers. This came about when the isthmus was formed by rising from the sea bed three million years ago. Once separated, each of the seven species formed both an Atlantic and a Pacific species that has persisted successfully over that period of time.
Mutations occur at random, but with expected frequency, and most of them come to naught. Natural selection is more involved with preventing evolutionary change than driving it which results in a rather long process of microevolutionary alteration due to environmental changes and species adaptations to achieve macroevolutionary change, especially speciation–roughly 100,000 to 5,000,000 years to evolve two reproductively isolated descendants. It is appropriate to ask if there has been enough time in earth’s existence and especially whether there has been enough time when the earthly environmental conditions were compatible with life to develop the known ±10 million species on earth today or especially the estimated 100 million potentially unknown species. Mathematically, starting with a single species 3.5 billion years ago and allowing for a split into two descendants only every 200 million years, there would have been plenty of time to achieve even the possible 100 million living species and even taking into account the myriads of species that have become extinct during that period of time.
Evolution Blogspot 7. Expanded Definitions, Part VI
The theory or law of evolution is often disparaged by the statement that it is “only a theory” by those who fear the implications of the science involved. They are correct that it is a theory, although they evidently are unaware of or choose to ignore the scientific definition of a theory. They would be more disparaging and even less accurate if the referred to Darwin’s concepts as an “hypothesis” meaning that it is little more than a hunch or a guess. The purpose of this blogspot is to set the record straight, at least insofar as science is concerned.
19. Theory: The National Academy of Science has defined a scientific theory as, “a well substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses”. In this definition, a theory is a more advanced, better tested, and more firmly established explanation than a guess, conjecture, or hypothesis. In science a theory such as the Theory of Evolution is a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence. The theory of gravity posits that forces of attraction exist that can be proved by mathematics and observable consequences–such as sending a space vehicle to orbit the earth or the moon. The law of gravity is considered to be a well established working theory of science despite the fact that it cannot be touched, heard, or seen directly. Physicists have studied extensively and understand the atom in great detail, but the fundamental nature of gravity still eludes them. Most educated people accept gravity as a given, but cannot bring themselves to accept evolution by natural selection. Nonetheless, evolution occupies in biology a position of acceptance on the order of the acceptance of gravity in physics. In brief, a scientific theory–a key to any scientific advance–in the words of physicist and Nobel Laureate, Jean Perrin, “is to be able to explain the complex visible by a simple invisible.” continued….
