Please wait while we process your payment
If you don't see it, please check your spam folder. Sometimes it can end up there.
Don’t have an account?
Create Your Account
Sign up for your FREE 7-day trial
Already have an account? Log in
Choose Your Plan
$4.99/month + tax
$24.99/year + tax
Save over 50% with a SparkNotes PLUS Annual Plan!
for a group?
Get Annual Plans at a discount when you buy 2 or more!
$18.74 /subscription + tax
Subtotal $37.48 + tax
on 2-49 accounts
on 50-99 accounts
Want 100 or more?
for a customized plan.
You'll be billed after your free trial ends.
7-Day Free Trial
Renews December 8, 2023
December 1, 2023
Discounts (applied to next billing)
This is not a valid promo code.
(one code per order)
Annual Plan - Group Discount
SparkNotes Plus subscription is $4.99/month or $24.99/year as selected above. The free trial period is the first 7 days of your subscription. TO CANCEL YOUR SUBSCRIPTION AND AVOID BEING CHARGED, YOU MUST CANCEL BEFORE THE END OF THE FREE TRIAL PERIOD. You may cancel your subscription on your Subscription and Billing page or contact Customer Support at email@example.com. Your subscription will continue automatically once the free trial period is over. Free trial is available to new customers only.
For the next 7 days, you'll have access to awesome PLUS stuff like AP English test prep, No Fear Shakespeare translations and audio, a note-taking tool, personalized dashboard, & much more!
You’ve successfully purchased a group discount. Your group members can use the joining link below to redeem their group membership. You'll also receive an email with the link.
Members will be prompted to log in or create an account to redeem their group membership.
Thanks for creating a SparkNotes account! Continue to start your free trial.
Your PLUS subscription has expired
See discount terms and conditions.
Darwin discusses the heritability of instinct and its role in natural selection. Instinct proves difficult for Darwin to define. It is similar to habit, because it consists of actions performed repeatedly by an individual animal. But unlike habit, which Darwin believes animals learn, instinct is inherited. The causes of innate instincts remain unknown, in the same way the causes of physical variations are unknown. Darwin believes that inherited habits—those learned by a parent and subsequently passed on to offspring by hereditary inheritance—may play a role in the construction of these instincts. However instincts come to be, Darwin argues that natural selection acts on them just as it acts on physical variations. If an instinct is advantageous to a species’ survival, natural selection allows organisms with that instinct to survive over others and perpetuate that instinct in their offspring. Thus, natural selection helps create entire species with well-adapted instincts, allowing them to survive in a variety of natural environments.
Darwin provides many examples of species that have innate, advantageous instincts. Certain hens, for example, have exhibited an instinct for laying their eggs in another hen’s nest, allowing them to give birth to numerous offspring without having to take care of all of them. In certain ant populations, some ants are born with “slave” instincts. These ants instinctively care for the rest of the population without any type of training after their birth. Hive bees instinctively construct the honeycomb to hold the greatest amount of honey possible. Darwin provides the results of a number of experiments in which the hive bees shaped whatever wax Darwin gave them, no matter what size or shape, in the same way. The results demonstrate that the construction of the hive holes is instinctual for the species. All of these instincts, Darwin argues, come about as a result of slight modifications over time: Natural selection perpetuates the most advantageous instincts, gradually honing them into their most advanced state in the latest incarnation of a species.
In concluding this chapter, Darwin presents one complication to his theory of the natural selection of instincts, a complication that, in his mind, almost destroys the entire theory. In some ant species, the worker ants, which vary from the nonworker ants in both structure and instinct, are sterile. If these ants are unable to produce offspring, how could their traits be inherited by subsequent generations? Moreover, a number of different structures for these infertile ants exist. How could all of these different structures be passed down through natural selection if the carriers of these structures were always infertile? While Darwin admits how difficult these questions are to answer, he argues that natural selection works on entire species, not just on individual organisms. Therefore, natural selection must have perpetuated the fertile ants in this species, the ones who carried a tendency to produce these sterile members, which proved advantageous to ant society by providing it with worker ants. The parent ants that were able to produce infertile offspring proliferated—not the sterile worker ants themselves. This difficult case illustrates the power of natural selection in selecting characteristics that could have been acquired only through variation and not through habit.
In his continued explanation of natural selection, Darwin discusses the heritability of instinct, shifting focus from the selection of physical characteristics to the selection of mental characteristics. This analysis builds on his previous discussion of natural selection but adds a new dimension: the power of mental characteristics (or instincts) to shape the survival and proliferation of species. Clearly, mere physical strength or structural adaptation is not enough for animals to survive in nature. Animals must know what to do with their physical adaptations and how to use them to live in their environment. They must know how to gather food, build shelter, and hide from their enemies. While the necessity of instincts may seem obvious, in this analysis, Darwin reminds the reader that advantages gained from instincts also become part of natural selection’s shaping of species.
Darwin’s discussion of advantageous mental characteristics in animals implies that organisms have an innate intelligence, and that some use this intelligence to survive better in nature. Darwin argues that the smartest animals are most likely to win out in natural selection, because their intelligence is advantageous to their survival. Indeed, many of the instincts he cites as examples, such as the mathematical precision of hive bees as they make honeycombs, are quite sophisticated. Darwin’s theory of heritability and natural selection of instincts implies that a form of intelligence plays a role in the development of the human species. Social Darwinists would later apply Darwin’s theory of natural selection to questions of human intelligence and how it shapes the human population. They would ask, Is natural intelligence in human beings instinctive and therefore innate, because it is passed on through heredity by innately intelligent parents? Do more intelligent human beings stand a greater chance of survival? Are intelligent humans naturally selected to survive and flourish in the human population?
Although Darwin admits that habit may play some unknown role in the development of variation, he provides an example of a hereditary characteristic—the birthing of sterile worker ants—that would be impossible to shape by habit or choice. Since the characteristic of sterility in worker ants is clearly inherited, some other means of creating variations must exist for these variations to be passed down to subsequent generations. Although Darwin cannot pinpoint the means by which these variations are created—Mendelian genetics and genetic mutation theory would provide those answers in the twentieth century—his example of the sterile worker ants provides a direct refutation of Lamarck’s evolutionary theory. Darwin points this out by asking how an instinct to reproduce sterile ants could be produced through chosen habit. Darwin’s “difficult case” of the sterile worker ants, which he believes could have undermined his own theory, ends up strengthening it instead by refuting the central assumption of Lamarckian evolution—that habits are the cause of evolution.
Ace your assignments with our guide to On the Origin of Species!