human
But as, through the diffusion of organisms and consequent differential actions of inorganic forces, there arose unlikenesses among them, producing varieties, species, genera, orders, classes, the actions of organisms on one another became new sources of organic modifications.
gpt
Always there must have been, and always there must continue to be, a survival of the fittest: natural selection must have been in operation at the outset, and can never cease to operate! While organisms had small abilities of co-ordinating their actions and actively adjusting themselves, natural selection worked almost alone in moulding and remoulding organisms into fitness for their changing environments, but as activity increased and brains grew, the power of varying actions to fit varying requirements became considerable.
human
As fast as essential faculties multiply, and as fast as the number of organs which co-operate in any given function increases, indirect equilibration through natural selection becomes less and less capable of producing specific adaptations; and remains capable only of maintaining the general fitness of constitution to conditions. The production of adaptations by direct equilibration then takes the first place: indirect equilibration serving to facilitate it. Until at length, among the civilised human races, the equilibration becomes mainly direct: the action of natural selection being limited to the destruction of those who are too feeble to live, even with external aid.
gpt
; in other words new patterns arise from the mingling of diverse hereditary contributions in fertilisation. _Secondly_, functional variation in the parents produces unlikeness in the offspring; those begotten under different constitutional states are different. In other words, fluctuations of nutrition in the parental body may cause variations in the germ-plasm. [In mammals there are also _modifications_ produced during the pre-natal life of the offspring which are congenital in the sense that they are present at birth in latent or patent form, which do not, however, really affect the germ-plasm since they disappear in the third generation.] _Thirdly_, an organism exposed to a marked change of external conditions, may have its equilibrium altered, and the offspring may be influenced.
human
The larger functional variations produced by greater external changes, are the initiators of those structural variations which, when once commenced in a species, lead by their combinations and antagonisms to multiform results. Whether they are or are not the direct initiators, they must still be the indirect initiators.
gpt
variations, which could not be referred to the causes noticed above. He attributed these to the fact that no two ova, no two spermatozoa, can be identical, since the process of nutrition cannot be absolutely alike. Minute initial differences in the proportions of the physiological units will lead, during development, to a continual multiplication of differences.
human
The insensible divergence at the outset will generate sensible divergences at the conclusion. This is not different from the general idea that nutritive fluctuations in the body provoke variations in the complex germ-plasm,
gpt
spontaneous variation
human
Here, then, we have a clue to the multiplied variations, and sometimes extreme variations, that arise in races which have once begun to vary. Amid countless different combinations of units derived from parents, and through them from ancestors, immediate and remote--and the various conflicts in their slightly different organic polarities, opposing and conspiring with one another in all ways and degrees, there will from time to time arise special proportions causing special deviations. From the general law of probabilities it may be concluded that while these involved influences, derived from many progenitors, must, on the average of cases, obscure and partially neutralise one another; there must occasionally result such combinations of them as will produce considerable divergences from average structures; and at rare intervals, such combinations as will produce very marked divergences. There is thus a correspondence between the inferable results and the results as habitually witnessed.
gpt
The members of a species inhabiting any area cannot be subject to like sets of forces over the whole of that area. And if, in different parts of the area, different kinds or amounts or combinations of forces act on them, they cannot but become different in themselves and in their progeny. To say otherwise, is to say that differences in the forces will not produce differences in the effects; which is to deny the persistence of force.
human
gpt
That natural selection is, and always has been, operative is incontestable.... The survival of the fittest is a necessity, its negation is incontestable.
human
or
gpt
The Social Organism
human
The different parts of a social organism, like the different parts of an individual organism, compete for nutriment; and severally obtain more or less of it according as they are discharging more or less duty. (See also _Essays_, i. 290.) And, again, in 1876, in his _Principles of Sociology_, he amplified his statement thus:
gpt
All other organs, therefore, jointly and individually, compete for blood with each organ,... local tissue formation (which under normal conditions measures the waste of tissue in discharging function) is itself a cause of increased supply of materials... the resulting competition, not between units simply, but between organs, causes in a society, as in a living body, high nutrition and growth of parts called into the greatest activity by the requirements of the rest. And once more:
human
For clearly, if the survival of the fittest among organisms is a process of equilibration between actions in the environment and actions in the organism; so must the local modifications of their parts, external and internal, be regarded as survivals of structures, the reactions of which are in equilibrium with the actions they are subject to. Clearly Spencer had a prevision of what Roux calls
gpt
(The struggle of parts within the organism), and we have here another example of his biological insight. That Spencer was not far from the idea of a struggle between hereditary units, we see from the following passage:
human
In the fertilised germ we have two groups of physiological units, slightly different in their structures. These slightly different units severally multiply at the expense of the nutriment supplied to the unfolding germ--each kind moulding this nutriment into units of its own type. Throughout the process of development the two kinds of units, mainly agreeing in their proclivities and in the form which they tend to build themselves into, but having minor differences, work in unison to produce an organism of the species from which they were derived, but work in antagonism to produce copies of their respective parent-organisms. And hence ultimately results an organism in which traits of the one are mixed with traits of the other; and in which, according to the predominance of one or other group of units, one or other sex with all its concomitants is produced
gpt
Either there has been inheritance of acquired characters or there has been no evolution.
human
The general argument proceeds upon the analogy between natural selection and artificial selection. Yet all know that the first cannot do what the last does. Natural Selection can do nothing more than preserve those of which the _aggregate_ characters are most favourable to life. It cannot pick out those possessed of one particular favourable character, unless this is of extreme importance.