If ever you wondered what the “default” view was before the modern era began with the late 18th century naturalists, culminating in Darwin, regarding the natural world, this passage, from a philosopher with the odiferous name William Smellie, gives a complete summary.
From Smellie, William. 1791. The philosophy of natural history. Philadelphia: Robert Campbell, pp463-469.
Of the Progressive Scale or Chain of Beings in the Universe.
TO men of observation and reflection, it is apparent, that all the beings on this earth, whether animals or vegetables, have a mutual connection and a mutual dependence on each other. There is a graduated scale or chain of existence, not a link of which, however seemingly insignificant, could be broken without affecting the whole. Superficial men, or, which is the same thing, men who avoid the trouble of serious thinking, wonder at the design of producing certain insects and reptiles. But they do not confider that the annihilation of any one of these species, though some of them are inconvenient, and even noxious to man, would make a blank in Nature, and prove destructive to other species who feed upon them. These, in their turn, would be the cause of destroying other species, and the system of devastation would gradually proceed, till man himself would be extirpated, and leave this earth destitute of all animation.
In the chain of animals, man is unquestionably the chief or capital link, and from him all the other links descend by almost imperceptible gradations. As a highly rational animal, improved with science and arts, he is, in some measure, related to beings of a superior order, wherever they exist. By contemplating the works of Nature, he even rises to some faint ideas of her great Author. Why, it has been asked, are not men endowed with the capacity and powers of angels? beings of whom we have not even a conception. With the same propriety, it may be asked, why have not beasts the mental powers of men? Questions of this kind are the results of ignorance, which is always petulant and presumptuous.  Every creature is perfect, according to its destination. Raise or depress any order of beings, the whole system, of course, will be deranged, and a new world would be necessary to contain and support them. Particular orders of beings should not be considered separately, but by the rank they hold in the general system. From man to the minutest animalcule which can be discovered by the microscope, the chasm seems to be infinite: But that chasm is actually filled up with sentient beings, of which the lines of discrimination are almost imperceptible. All of them possess degrees of perfection or of excellence proportioned to their station in the universe. Even among mankind, which is a particular species, the scale of intellect is very extensive. What a difference between an enlightened philosopher and a brutal Hottentot? Still, however, Nature observes, for the wisest purposes, her uniform plan of graduation. In the human species, the degrees of intelligence are extremely varied. Were all men philosophers, the business of life could not be executed, and neither society, nor even the species, could long exist. Industry, various degrees of knowledge, different dispositions, and different talents, are great bonds of society. The Gentoos [Hindus], from certain political and religious institutions, have formed their people into different casts or ranks, out of which their posterity can never emerge. To us, such institutions appear to be tyrannical, and restraints on the natural liberty of man. In some respects they are so: But they seem to have been originally results of wisdom and observation; for, independently of all political institutions, Nature herself has formed the human species into casts or ranks. To some she gives superior genius and mental abilities; and, even of these, the views, the pursuits, and the tastes, are most wonderfully diversified.
In the talents and qualities of quadrupeds of the same species, there are often remarkable differences. These differences are conspicuous in the various races of horses, dogs, &c. Even among the same races, some are bold, sprightly, and sagacious. Others are comparatively timid, phlegmatic, and dull.
 Our knowledge of the chain of Intellectual and corporeal beings is very imperfect; but what we do know gives us exalted ideas of that variety and progression which reign in the universe. A thick cloud prevents us from recognising the most beautiful and magnificent parts of this immense chain of being. We shall endeavour, however, to point out a few of the more obvious links of that chain, which falls under our own limited observation.
Man, even by his external qualities, stands at the head of this world. His relations are more extensive, and his form more advantageous, than those of any other animal. His intellectual powers, when improved by society and science, raise him so high, that, if no degrees of excellence existed among his own species, he would leave a great void in the chain of being. Were we to confider the characters, the manners, and the genius of different nations, of different provinces and towns, and even of the members of the fame family, we should imagine that the species of men were as various as the number of individuals. How many gradations may be traced between a stupid Huron, or a Hottentot, and a profound philosopher? Here the distance is immense; but Nature has occupied the whole by almost infinite shades of discrimination.
In descending the scale of animation, the next step, it is humiliating to remark, is very short. Man, in his lowest condition, is evidently linked, both in the form of his body and the capacity of his mind, to the large and small orang-outangs. These again, by another slight gradation, are connected to the apes, who, like the former, have no tails. It is wonderful that Linnaeus, and many other naturalists, should have overlooked this gradation in the scale of animals, and maintained, that the island of Nicobar, and some other parts of the East Indies, were inhabited by tailed men. Before those animals whose external figure has the greatest resemblance to that of man, are ornamented, or rather deformed, with tails, there are several shades of discrimination. The larger and smaller orang-outangs, which are real brutes, have no tails. Neither  are the numerous tribes of apes furnished with this appendage. But the believers in tailed men gravely tell us, that there is nothing surprising in this phenomenon, because a tail is only a prolongation of the os coccygis, which is the termination of the back-bone. They consider not, however, that, instead of accounting for the existence of tailed men, they do nothing more than substitute a learned circumlocution for the simple word tail. It is here worthy of remark, that a philosopher, who has paid little attention to natural history, is perpetually liable to be deceived; and that a naturalist, I mean a nomenclator, without philosophy, though he may be useful by mechanically marking distinctions, is incapable of enriching our minds with general ideas. A proper mixture of the two is best calculated to produce a real philosopher. From the orang-outangs and apes to the baboons, the interval is hardly perceptible. The true apes have no tails, and those of the baboons are very short. The monkeys, who form the next link, have long tails, and terminate this partial chain of imitative animals, which have such a detestable resemblance to the human frame and manners.
When examining the characters by which beings are distinguishable from each other, we perceive that some of them are more general, and include a greater variety than others. From this circumstance all our distributions into classes, orders, genera, and species, are derived. Between two classes, or two genera, however, Nature always exhibits intermediate productions so closely allied, that it is extremely difficult to ascertain to which of them they belong. The polypus, which multiplies by shoots, or by sections, from its body, connects the animal to the vegetable kingdom. Those worms which lodge in tubes composed of sand, seem to link the insects to the shell and crustaceous animals. Shell-animals and crustaceous insects make also a near approach to each other. Both of them have their muscles and instruments of motion attached to external instead of internal bones. From reptiles, the degrees of perfection in animal life and powers move forward  in a gradual but perceptible manner. The number of their organs of sense, and the general conformation of their bodies, begin to have a greater analogy to the structure of those animals which we are accustomed to confider as belonging to the more perfect kinds. The snake, by its form, its movements, and its mode of living, is evidently connected with the eel and the water-serpent. Like reptiles, most fishes are covered with scales, the colours and variety of which often enable us to distinguish one species from another. The forms of fishes are exceedingly various. Some are long and slender; others are broad and contracted. Some fishes are flat, others cylindrical, triangular, square, circular, &c. The fins of fishes, from the medium in which they live, are analogous to the wings of birds. Like those of reptiles, the heads of fishes are immediately connected to their bodies, without the intervention of necks. The flying fishes, whose fins resemble the wings of bats, form one link which unites the fishes to the feathered tribes. Aquatic birds succeed, by a gentle gradation, the flying fishes.
In tracing the gradations from fishes to quadrupeds, the transition is almost imperceptible. The sea-lion, the morse, all the cetaceous tribes, the crocodile, the turtle, the seals, have such a resemblance, both in their external and Internal structure, to terrestrial quadrupeds, that some naturalists, in their methodical distributions, have ranked them under the same class of animals. The bats and the flying squirrels, who traverse the air by means of membranous instead of feathered wings, evidently connect quadrupeds with birds. The ostrich, the cassowary, and the dodo, who rather run than fly, form another link between the quadruped and the bird.
All the substances we recognise on this earth may be divided into organised and animated, organised and inanimated, and unorganised, or brute matter. The whole of these possess degrees of perfection, of excellence, or of relative utility, proportioned to their stations or ranks in the universe. Change these stations or ranks, and another world would be necessary to contain and support  them. Beings must not be contemplated individually, but by their rank, and the relations they have to the constituent parts of the general system of Nature. Certain results of their natures we consider as evils. Destroy these evils, and you annihilate the beings who complain of them. The reciprocal action of the solids and fluids constitutes life, and the continuation of this action is the natural cause of death. Immortality on this earth, therefore, presupposes another system; for our planet has no relation to immortal beings. Every animal, and every plant, rises, by gentle gradations, from an embryo, or gelatinous state, to a certain degree of perfection exactly proportioned to their several orders. An assemblage of all the orders of relative perfection constitutes the absolute perfection of the whole. All the planets of this system gravitate toward the sun and toward each other. Our system gravitates towards other systems, and they to ours. Thus the whole universe is linked together by a gradual and almost imperceptible chain of existences both animated and inanimated. Were there no other argument in favour of the UNITY of DEITY, this uniformity of design, this graduated concatenation of beings, which appears not only from this chapter, but from many other parts of the book, seems to be perfectly irrefragable.
In contemplating Man, as at the head of those animals with which we are acquainted, a thought occurred, that no sentient being, whose mental powers were greatly superior, could possibly live and be happy in this world. If such a being really existed, his misery would be extreme. With senses more delicate and refined; with perceptions more acute and penetrating; with a taste so exquisite that the objects around him could by no means gratify it; obliged to feed upon nourishment too gross for his frame; he must be born only to be miserable, and the continuation of his existence would be utterly impossible. Even in our present condition, the sameness and insipidity of objects and pursuits, the futility of pleasure, and the infinite sources of excruciating pain, are supported with great difficulty by cultivated and refined minds. Increase our sensibilities, continue the same objects and situation,  and no man could bear to live. Let man, therefore, be contented. His station in the universal scale of Nature is fixed by Wisdom. Let him contemplate and admire the works of his Creator; let him fill up his rank with dignity, and consider every partial evil as a cause or an effect of general good. This is the whole duty of man.
Notice that extinction is prohibited; that there is a single gradual ladder of progressive life, and that nothing may change without upsetting the order of things. And of course, it all goes to show that God exists and is beneficent. When Darwin removed that certainty, whether he intended to or not, he shocked his readers. Anyway, I thought this was a fun piece.