Ayn Rand states that reason is Man’s only means to gain knowledge and that Man lacks instincts like the animals have. But I have trouble understanding how this would fit with the theory of evolution.
If humans evolved from lower species (early hominids) who relied on instincts to later become Homo sapiens who now rely only on reason, does that mean that at some point in our history we did rely on instincts and that somehow reason slowly started to replace instincts as our only means of survival?
If that is the case wouldn’t we logically have a bit of instincts residue in us?
How would it be possible that instincts completely got replaced with reason in Homo sapiens?
I guess those are very difficult questions to answer but are there any Objectivist views on this that would help explain this mechanism in more detail?
The Objectivist view of "instincts" is succinctly summarized in The Ayn Rand Lexicon under the topic of "'Instinct'." The second excerpt in that topic comes from Ayn Rand's article, "The Anti-Industrial Revolution," which is a refined version of a very similar formulation from Journals of Ayn Rand, pp. 251-252 (underline added):
Man comes on earth unarmed. His brain is his only weapon. Animals obtain food by force guided by instinct. Man has no claws, no fangs, no horns, no great strength of muscle, and no instinct to guide him. He cannot obtain sustenance for his body except through the exercise of his rational faculty.
Note that for animals, survival depends on force as well as instinct. Animals have the biological features to facilitate their use of physical force. In the study of human evolution, therefore, the anatomical attributes of man are highly significant. Instinct alone is impotent.
I found two apparently very helpful Wikipedia articles on biological evolution:
At 7 Ma ("Ma" means million years ago), the timeline  shows an extinct chimp-like primate believed by some to be the last common ancestor between hominids and chimps, even though modern humans and modern chimps still show remarkable similarity in their DNA:
The development of molecular genetics has revealed the record of evolution left in organisms' genomes: dating when species diverged through the molecular clock produced by mutations. For example, these DNA sequence comparisons have revealed that humans and chimpanzees share 98% of their genomes and analysing the few areas where they differ helps shed light on when the common ancestor of these species existed.
(Excerpted from .) At 6 Ma, the timeline  mentions a clear divergence in the genetic line for hominids. But the hominids were not modern man. Anatomical changes continued to evolve, leading to homo erectus at 1.8 Ma:
Homo erectus would bear a striking resemblance to modern humans, but had a brain about 74 percent of the size of modern man. Its forehead is less sloping than that of Homo habilis and the teeth are smaller.
The "Homo" line continued to evolve through about 200 Ka (thousand years ago), when we finally reach modern man, homo sapiens sapiens.
How did the early hominids and homo species survive? It's really the task of the special sciences such as evolutionary biology to answer this. It cannot be answered by Objectivism or any other philosophy. Ayn Rand's comments about animals versus man pertain primarily to what we can observe in today's animals and humans, not to issues specific to extinct intermediate species in the distant past. But neither can philosophy say (nor does Objectivism say) that a gradual evolution of increasing survival dependence on conceptual cognition (in man) would have been impossible. Increasing conceptual capacity surely tends to make survival easier for humans, even as they must still rely on physical force for survival (especially against non-human animal species). Intelligence gives humans a clear survival advantage over other species when it has sufficient opportunity to operate.
Remember, also, that animals survive by sensory-perceptual cognition and automatic "values" (goal-directedness), which may include "instincts" but is not necessarily equivalent to instincts alone.
The question also asks:
...wouldn’t we logically have a bit of instincts residue in us?
The term "instinct" is sometimes used very loosely in regard to man to refer to phenomena such as desires, urges, reflexes, automatized habits and/or skills, and so on. In that sense, yes, man does still have the capacity to this day to attempt to function without thinking. The point that Objectivism makes is that man today cannot survive that way; he cannot achieve man's life qua man. But earlier hominid ancestors, with significantly more primitive anatomical features, might very well have been able to survive in the form that their natures allowed -- until climate conditions changed or they came into competition with other, more adapted species, etc.
answered Mar 29 '15 at 19:24
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