The Great Ideas ~ The Darwinian Theory of Man's Origin

From How Different Are Humans? we move to the Darwinian Theory of Man, the argument and evidence for his origin and nature.  While Darwin did not present his theory until his second book, The Descent of Man, he relied on his first book, Origin of Species for the truths of his theory.

This is a tough chapter with complex ideas so bear with me.  I'm going to use many of Adler's quotes. Darwin's argument in The Descent of Man is structured as follows:

1. man differs only in degree from other animals;
2. man's origin can be like that of other species;
3. if man's origin were like that of other species, then missing links must have existed and must be discovered.

His whole argument is dependent on this first proposal being true; there can be no missing links if "there are no intermediate varieties possible between man and ape" and therefore no intermediate varieties are possible if man differs in "kind" from other animals, instead of by "degree".

Luckman protests that the scientific people he spoke with claim that there are only two positions: 1) a difference in degree only and; 2) that any differences in kind are always reducible to differences in degree.

Adler says that these people "beg the question" (begging the question is a logical fallacy when an argument's premises assume the truth of the conclusion instead of supporting it).  They are right if things only differ in degree but they cannot say that the difference between kind and degree is indiscernible.  They cannot say that a difference in kind is reducible or a difference in degree is large enough to make a divergence to kind.  They cannot say that the difference between kind and degree is unintelligible because the fact they recognize a difference exists, makes their argument unintelligible.

Adler goes on to answer questions and observations from letters he received that support his point.  Then he moves on to the question, "how does man differ from other animals with or without intermediates, intermediate varieties?"

Ape in the Orange Grove (1910)
Henri Rousseau
source Wikiart

The Main Point of Darwin's Theory

Both Hume and Kant noted that man differs from other animals by degree alone with intermediate varieties hundreds of years before Darwin.  So what did Darwin add to the insistence on difference in degree?  He took their point and expanded it to theorize about man's origin which brought about his theory of evolution.

There are three main points to his theory:

1. from generation to generation organisms vary by hereditary
2. there is an accumulation and persistence of extreme variety
3. this persistence of extreme variety is accompanied by the extinction of intermediate varieties (if this was not so, there'd be no origin of species)

In Darwin's own words, "On the theory of natural selection the extinction of old forms and the production of new are intimately connected ... The only distinction between species and well-marked varieties is that the latter are known or believed to be connected at the present day with intermediate graduations. .... numberless intermediate varieties linking closley together all the species of the same group most assuredly have existed.  The number of intermediate and transitional links between all living and extant species must have been inconceivably great.  Yet, if this theory is true, they must have all existed at the same time on earth, linking together all the species in each group by graduation as fine as our existing varieties."

Adler states that if all the intermediate varieties co-existed at the same time today as the other species, there would be no species because "you would have a continuous connection of one with another."  Darwin claims the extinct fossil remains connecting man to ape exist, but simply haven't been discovered yet.  Under the assumption that man differs only in degree from apes, then the fossil remains do indeed form the missing link. Adler then lists man along with four anthropoid apes.

Man and Ape (2013)
Stanley Pinker
source Wikiart

Mental Differences Between Apes and Humans

The fossil remains are often reconstructions from a few bones, in particular the jawbone or skull bones and only point to a physical resemblance between man and ape. Luckman points out there are physiological and embryological resemblances as well and Adler agrees, but in addition to resemblances, there are enormous differences.  Yet he asks, scientifically how is ape separated from man?  The species of man is Homo sapien, therefore being sapient enough to have the intelligence to become wise and that is the main point; the mental difference is what is important, not the physical similarities or differences. The most important question remains; are the differences between man and ape kind or degree, and are they bridgeable?  If they are, the fossil remains can be missing links but if they are not, the fossil remains prove nothing.  Then, even if evolution can account for the origin of man's body, it cannot account for the origin of man's mind.

Luckman asks from a letter he received, why a highly rational species cannot have evolved fom a less-developed one.  Adler also points to another letter that asks why God cannot have created a rational man from a rationally undeveloped ape.  There is also a speculation of a new "ingredient" being added at the moment of man's origin, separating him from ape.

Allegory: boy lighting a candle in the company of an ape and a fool - Fábula (c. 1590)
El Greco
source Wikiart

Alder circles back to Darwin's argument which did not depend on the anatonomical or physiological resemblances, but man's mental development, knowing full well his argument would not stand if the two were not linked.  He quotes Darwin's words: "My object is to show that there is no fundamental difference between man and the higher mammals in their mental faculties.  Animals possess the power of reasoning just as much as men do ..." He says they can speak abstractly, understand human speech, etc. He claims though if there is a difference mentally, it is only of degree.

Next time, Adler says he will share more of Darwin's reasoning, and add to it evidence that has been done since then in animal learning, speech and thought, which he says gives strong evidence for the evolutionary theory.  However, if this evidence was indisputable, the matter would have ended  But Adler says it can be disputed and he will present equally compelling evidence in the next discussion, The Answer to Darwin.

My apologies for the length of the post.  It helped me to try to get my head around Adler's ideas, and of course, Darwin's. I hope it didn't put the rest of you to sleep! :-)