Ernst Mayr Quotes - Page 2

Evolution thus is merely contingent on certain processes articulated by Darwin: variation and selection.

A new species develops if a population which has become geographically isolated from its parental species acquires during this period of isolation characters which promote or guarantee reproductive isolation when the external barriers break down.

Living in an entirely different physical as well as biotic environment, such a population would have unique opportunities to enter new niches and to select novel adaptive pathways.

Definitions are temporary verbalizations of concepts, and concepts- particularly difficult concepts- are usually revised repeatedly as our knowledge and understanding grows.

Isolating mechanisms are biological properties of individuals that prevent the interbreeding of populations that are actually or potentially sympatric.

As a consequence, geneticists described evolution simply as a change in gene frequencies in populations, totally ignoring the fact that evolution consists of the two simultaneous but quite separate phenomena of adaptation and diversification.

Biology can be divided into the study of proximate causes, the study of the physiological sciences (broadly conceived), and into the study of ultimate (evolutionary) causes, the subject of natural history.

It is curious how often erroneous theories have had a beneficial effect for particular branches of science.

There are a number of attributes of species and populations that are not of any particular selective advantage to any single individual in a population but that are of great advantage to the population as a whole.

Indeed, I was unable to find any evidence whatsoever of the occurrence of a drastic evolutionary acceleration and genetic reconstruction in widespread, populous species.

To take an unequivocal stand, it seems to me, is of greater heuristic value and far more likely to stimulate constructive criticism than to evade the issue.

Given the fact of evolution, one would expect the fossils to document a gradual steady change from ancestral forms to the descendants. But this is not what the paleontologist finds. Instead, he or she finds gaps in just about every phyletic series.

The reduced variability of small populations is not always due to accidental gene loss, but sometimes to the fact that the entire population was started by a single pair or by a single fertilized female. These 'founders' of the population carried with them only a very small proportion of the variability of the parent population. This 'founder' principle sometimes explains even the uniformity of rather large populations, particularly if they are well isolated and near the borders of the range of the species.

anyone who writes about "Darwin's theory of evolutionin the singular, without segregating the theories of gradual evolution, common descent, speciation, and the mechanism of natural selection, will be quite unable to discuss the subject competently.

I had found again and again that the most aberrant population of a species - often having reached species rank, and occasionally classified even as a separate genus - occurred at a peripheral location, indeed usually at the most isolated peripheral location.

In those early years in New York when I was a stranger in a big city, it was the companionship and later friendship which I was offered in the Linnean Society that was the most important thing in my life.

It seems to me that for Darwin the pulsing of evolutionary rates was a strictly vertical phenomenon.

Two forms or species are sympatric, if they occur together, that is if their areas of distribution overlap or coincide. Two forms (or species) are allapatric, if they do not occur together, that is if they exclude each other geographically. The term allopatric is primarily useful in denoting geographic representatives.

In neither his definition nor the examples illustrating what memes are does Dawkins mention anything that would distinguish memes from concepts.