Co-operation, including seemingly altruistic behaviours can be advantageous
when there is Reciprocity. This theory of reciprocal altruism provides one
explanation for cases of seemingly altruistic behaviour by various animals (for
example, sharing of blood meal in vampire bats). Under which of the following
conditions this theory cannot be used as an explanation of co-operative
behaviour?
The animal is an invertebrate
The animal is distributed such that repeated encounter between
conspecifics is very rare
The animal cannot recognize kins from non-kins
The animal can recognize non-kins, but cannot distinguish between close
and distant distant genetic relatives
The theory of reciprocal altruism cannot be used to explain cooperative behaviour when the animal is distributed such that repeated encounters between conspecifics are very rare. Repeated interactions are a core requirement for reciprocity to be favoured by natural selection.
Introduction (SEO optimized)
Reciprocal altruism is an evolutionary theory that explains why animals sometimes help non-kin at a cost to themselves, expecting that the help will be returned in future interactions. Classic examples include food sharing in vampire bats, where an individual that has fed successfully shares blood with a hungry roost-mate and may later receive help when it fails to feed. For reciprocal altruism to evolve and remain stable, several key conditions must be satisfied, and understanding these conditions is crucial for solving conceptual MCQs in ecology and evolutionary biology.
Core idea of reciprocal altruism
Reciprocal altruism, first formalized by Robert Trivers, describes a situation where an individual performs a costly act that benefits another, with the expectation (or evolved probability) that the favour will be returned later. Game-theoretic models like the iterated Prisoner’s Dilemma show that cooperation can be favoured when individuals interact repeatedly and can adjust their behaviour based on partners’ past actions.
Key necessary conditions usually include:
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Repeated interactions between the same individuals.
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Ability to recognize and remember partners.
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Non-trivial benefit to the recipient and cost to the actor.
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Mechanism to limit cheating or preferentially help reciprocators.
MCQ: Which condition rules out reciprocal altruism?
Question (conceptual):
“Under which of the following conditions can the theory of reciprocal altruism not be used as an explanation of cooperative behaviour?”
Options:
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The animal is an invertebrate
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The animal is distributed such that repeated encounter between conspecifics is very rare
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The animal cannot recognize kins from non-kins
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The animal can recognize non-kins, but cannot distinguish between close and distant genetic relatives
Correct answer:
(2) The animal is distributed such that repeated encounter between conspecifics is very rare.
Reason: Reciprocal altruism requires a high probability that the same individuals will meet again, so that the beneficiary can repay the favour and cheaters can be detected and punished. If repeated encounters are very rare, individuals cannot base their strategy on past interactions with specific partners, and selection cannot favour “help now, be repaid later” strategies.
Detailed explanation of each option
Option 1: Animal is an invertebrate
Being an invertebrate does not, by itself, rule out reciprocal altruism. What matters is cognitive capacity for partner recognition, memory of interactions, and population structure allowing repeated encounters, not vertebrate vs invertebrate status. Some invertebrates (e.g., certain social insects or crustaceans) can show sophisticated social interactions and repeated contacts, so in principle reciprocal altruism could evolve in them as long as the key conditions are met.
Therefore, Option 1 is incorrect as a blanket statement, because reciprocal altruism is not restricted to vertebrates.
Option 2: Repeated encounters are very rare (Correct)
If individuals are distributed so that repeated encounters between conspecifics are very rare, the probability that a donor will ever meet the same recipient again is extremely low. Under such conditions:
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A cooperator that helps today is unlikely to be repaid by the same individual in the future.
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Cheaters (those who accept help and never reciprocate) cannot be effectively punished or avoided because there is little or no partner-specific history.
Evolutionary and game-theoretic models show that reciprocity is favoured only when the expected number of future interactions is sufficiently high—essentially when the “shadow of the future” is long. Therefore, Option 2 directly violates one of the fundamental requirements for reciprocal altruism and is the correct answer.
Option 3: Animal cannot recognize kin from non-kin
Not being able to distinguish kin from non-kin affects kin selection, not reciprocal altruism. Reciprocal altruism is based on repeated interactions and partner-specific reciprocity, irrespective of genetic relatedness; help can be exchanged among unrelated individuals as long as they can remember one another and respond to past behaviour.
An animal could fail to recognize kin yet still recognize individual partners (e.g., by visual, chemical, or auditory cues) and adjust its cooperation based on previous encounters. Thus, reciprocal altruism can still operate even if kin recognition is absent, provided individual recognition and repeated interactions are possible. Therefore, Option 3 does not rule out reciprocal altruism and is incorrect as the answer.
Option 4: Recognizes non-kin but not degree of relatedness
In this condition, the animal can tell that another individual is a non-kin but cannot distinguish between close and distant genetic relatives among non-kin. For reciprocal altruism, what matters is whether the individual can:
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Recognize particular partners as individuals.
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Track who has cooperated or defected in past interactions.
Fine-scale discrimination among close vs distant relatives is essential for precise kin-selection strategies, but not for reciprocity-based cooperation. As long as individual identity and interaction history are available, reciprocal altruism can still function. Therefore, Option 4 also does not invalidate reciprocal altruism and is incorrect as the chosen condition.
Key exam takeaways
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Reciprocal altruism explains cooperative acts towards non-kin when there is an expectation of future reciprocation, supported by repeated interactions and partner recognition.
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The critical condition that must not be violated is the occurrence of repeated encounters between the same individuals; if such encounters are rare, reciprocity cannot be maintained.
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Kin recognition is not a requirement for reciprocal altruism; it is a requirement for kin selection, which is a different mechanism explaining altruism among genetic relatives.
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When answering MCQs, always link back to the formal conditions of reciprocal altruism: repeated interactions, partner recognition, memory, and mechanisms that make cheating disadvantageous.
