Huxley's On the Origin of Species

If there is any author associated with the book title On the Origin of Species it is most certainly Charles Darwin, yet Darwin was not the only person to pen a book beginning with those words. The full title of Darwin's first edition was On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life, but about two decades later another On the Origin of Species would be published bearing Thomas Henry Huxley's name. With the full title On the Origin of Species: Or, the Causes of the Phenomena of Organic Nature, the book was a compilation of six lectures Huxley had designed for lay audiences about evolution. This was not a scientific treatise but a quick, plain overview of evolution, and in the introduction of the 1881 American edition an anonymous editor made the need for such a work clear;

The publication of Mr. Darwin's work on the "Origin of Species," whether we consider the importance of the questions it raises, the ability with which he treats them, the boldness and originality of his speculations, or the profound and universal interest which the book awakened, must be looked upon as marking an era in the progress of science. But while it called forth a due share of candid discussion and intelligent criticism, it has been vehemently and persistently assailed by many who understood nothing of its real character; and the subject has hence been so overloaded with prejudice and perversion that unscientific people hardly know what to think or believe about it.

The contents of the book, derived from notes on Huxley's "Lectures to Working Men," had been transcribed by J. Aldous Mays. Huxley acceded to the publication of the work provided that it be noted that he did not have the opportunity to review or revise what he had said prior to the publication of the book.

Huxley began his lectures with a discussion about the horse. Surely his would be familiar with what a horse was and what it looked like, and Huxley used a few equine illustrations to introduce not only the anatomy of the horse, but different modes of scientific inquiry. Telling the listeners to imagine Huxley sawing a horse into anterior and posterior halves, Huxley called the audience's attention to a simple diagram illustrating the location of the spine, heart, and other features. "Now that is a horse - as mathematicians would say - reduced to its most simple expression," Huxley quipped.

Once Huxley had broken down the horse into its constituent parts he could place the whole organism in environmental context, from cycles of life & death to biogeography. Yet Huxley was not on to evolution just yet. Although he is remembered as "Darwin's Bulldog" he had his own paleontological and anatomical programs, lines of inquiry that centered on form. Where Richard Owen's concept of the vertebrate Archetype was Platonic and little more than a blueprint (a thought in the mind of the Architect), in Huxley's program similar ground plans had been inherited and modified via evolution. Even beyond the vertebrates, Huxley underlined the unity of all life, from plants to our own species.

In the next lecture Huxley moved from the "organic world" to the inorganic, providing an extensive overview of geology and fossilization. The great expanse of time separating the present from the strange and different past was the main feature of this lecture. The fossil record was certainly faulty and incomplete, Huxley said, but it was not incomprehensible. What had been found could be understood, even if the Connecticut Valley trackmakers and bodies of the owners of the Stonesfield jaws were still missing. Part of the reason for this was that the remains of ancient creatures appeared to belong to groups still living; among 120 recognized Orders Huxley identified only about a dozen (like plesiosaurs and pterodactyls) that had gone entirely extinct. Indeed, at the level of Order, extinction was seen as a rarity. Still, the members of Orders differed the deeper one looked in the strata. Life had changed.

Where the second lecture had been packed with geological tidbits, Huxley prefaced the third (on the subject of "The Origination of Living Beings") by reiterating that science was not a modern "black art." Huxley took aim at those who would prefer "miraculous" explanations of nature;

To such sincere and earnest persons, I would only say, that a question of this kind is not to be shelved upon theoretical or speculative grounds. You may remember the story of the Sophist who demonstrated to Diogenes in the most complete and satisfactory manner that he could not walk ; that, in fact, all motion was an impossibility ; and that Diogenes refuted him by simply getting up and walking round his tub. So, in the same way, the man of science replies to objections of this kind, by simply getting up and walking onward, and showing what science has done and is doing, -- by pointing to that immense mass of facts which have been ascertained and systematized under the forms of the great doctrines of Morphology, of Development, of Distribution, and the like. He sees an enormous mass of facts and laws relating to organic beings, which stand on the same good sound foundation as every other natural law ; and, therefore, with this mass of facts and laws before us, seeing that, as far as organic matters have hitherto been accessible and studied, they have shown themselves capable of yielding to scientific investigation, we may accept this as proof that order and law reign there as well as in the rest of nature ; and the man of science says nothing to objectors of
this sort, but supposes that we can and shall walk to the origin of organic nature, in the same way that we have walked to a knowledge of the laws and principles of the inorganic world.

Indeed, while the previous lectures dove directly into what was essentially data, in this lecture Huxley took great pains to explain that science could understand nature, the basic logical toolkit of science being accessible to everyone (and commonly used in day-to-day life). Armed with these tools, Huxley then reviewed how the hypothesis of spontaneous generation had been tested and refuted. Huxley could only admit his ignorance about the origin of life, but the "perpetuation of living beings" (the subject of the next lecture) provided more fertile grounds for discussion.

Huxley started, as with the other lectures, from the bottom up. Living organisms reproduce themselves, and those offspring vary from their parents. In farm animals those variations can be selected to create entirely new breeds. Yet variations between members of a population or species were not due to random mixing; certain traits or conditions were inherited from one generation to the next. The point of all this was to show that if certain heritable traits were selected for they could bring about the origin of new varieties of organisms, and Huxley kept on the details of artificial selection in the fifth lecture.

Was there a natural equivalent to human selective breeding? The actual origin of a natural variety had never been witnessed, said Huxley, but organisms in the wild both varied and were subject to certain causes that could act as selective forces. If it could happen before our eyes in the barnyard then why not in nature? Variation was certainly a fact, and the "struggle for existence" provided the selective force. To Huxley, the natural world was constantly embroiled in a kind of war, organisms replacing and extinguishing their predecessors and competitors as they evolved.

Finally, in the last lecture, Huxley set out to tackle the theoretical framework of Darwin's theory. Rather than directly trying to convince his audience Huxley took a critical approach, asking what if Darwin's predictions had been confirmed by the evidence. The splint bones in the leg of the horse and the teeth in fetal whales signaled in the affirmative, as did the graded succession of fossil forms in the geologic strata. Other evolutionary theories were consonant with such information, as well, but the piece of evidence that tipped the scale in Darwin's favor was the persistence of fossil forms. Under Darwin's environmentally-driven framework it would be expected that some groups of organisms would evolve under changing conditions and others, if subject to relatively stable conditions, would not change much at all. This concept of stasis coupled with evolution did more for Darwin's theory than any evidence of progressive change.

Something about artificial selection troubled Huxley, however. Domesticated animals had been bred to take on a variety of forms yet they could still interbreed. Natural selection seemed to offer no explanation for why this should be, particularly if the selection of humans was comparable to selection in nature. Why could some distinct species interbreed yet some more closely-related varieties not produce viable offspring? Huxley could find no satisfactory answers, yet as he said, "There is a wide gulf between the thing you cannot explain and the thing that upsets you altogether." Huxley thought that the vexing question may eventually be understood, and the fact that there was still more to learn did not overturn Darwin's theory. Nothing else seemed to come close to offering an explanation for the unity and diversity of life. "I really believe the alternative," Huxley opined, "is either Darwinism of nothing ..."

With the vast body of evidence about nature strongly in favor of Darwin, Huxley decided to drive home the point that humans were not exempt from evolution. Our power of speech might separate us from the rest of the animals, but what "separated us from the animals" was very slight and delicate. Indeed, where naturalists in the past had exalted the "fine tuning" of organisms to signal their creation by a benevolent deity, Huxley created his own watch analogy to demonstrate how slight differences can have enormous effects;

Take a couple of watches -- made by the same maker, and as completely alike as possible ; set them upon the table, and the function of each -- which is its rate of going -- will be performed in the same manner, and you shall be able to distinguish no difference between them ; but let me take a pair of pincers, and if my hand is steady enough to do it, let me just lightly crush together the bearings of the balance-wheel, or force to a slightly different angle the teeth of the escapement of one of them, and of course you know the immediate result will be that the watch, so treated, from that moment will cease to go. But what proportion is there between the structural alteration and the functional result ? Is it not perfectly obvious that the alteration is of the minutest kind, yet that slight as it is, it has produced an infinite difference in the performance of the functions of these two instruments ?

Whatever made us distinguishable from other creatures was certainly minute; little changes could have enormous effects. Darwin's theory perfectly meshed with this concept, and Huxley closed his series by noting that Darwin's On the Origin of Species would serve as a guide to nature for the next three or four generations. I wonder what he would think of next year's evolutionary celebrations...