Social selection

Key takeaways

Social selection belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Social selection to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Social selection from memory before moving on to harder problems.

Reference excerpt

Social selection is a term used with varying meanings in biology. Joan Roughgarden proposed a hypothesis called social selection as an alternative to sexual selection. Social selection is argued to be a mode of natural selection based on reproductive transactions and a two-tiered approach to evolution and the development of social behavior. Reproductive transactions refer to a situation where one organism offers assistance to another in exchange for access to reproductive opportunity. The two tiers of the theory are behavioral and population genetic. The genetic aspect states that anisogamy arose to maximize contact rate between gametes. The behavioral aspect is concerned with cooperative game theory and the formation of social groups to maximize the production of offspring. In her critique against the neo-Darwinian defense of sexual selection, Roughgarden outlines exceptions to many of the assumptions that come with sexual selection. These exceptions include sexually monomorphic species, species which reverse standard sex roles, species with template multiplicity, species with transgender presentation, frequencies of homosexual mating, and the lack of correlation between sexually selected traits and deleterious mutation. An article published by Roughgarden's lab on her ideas received criticism in the journal Science. Forty scientists produced ten critical letters. The critics stated that the article was misleading, that it contained misunderstandings and misrepresentations, that sexual selection accounted for all the data presented and subsumed in Roughgarden's theoretical analysis, and that sexual selection explained data that her theory could not. Other researchers, such as biologist Mary Jane West-Eberhard and evolutionary medicine researcher Randolph M. Nesse, instead view sexual selection as a subcategory of social selection, with Nesse and anthropologist Christopher Boehm arguing further that altruism in humans held fitness advantages that enabled evolutionarily extraordinary cooperativeness and the human capability of creating culture, as well as desertion, abandonment, banishment, and capital punishment by band societies against bullies, thieves, free-riders, and psychopaths.

Genetic principles

Portfolio hypothesis Short for the genetic-portfolio balancing hypothesis, this idea, proposed by Roughgarden, is used as an alternative to the Red Queen and Mueller's ratchet hypotheses to explain the existence of sexual reproduction within the framework of social selection. In a population with two species which fit the same ecological niche, live in the same local environment, have the same degree of genetic diversity, but have different modes of reproduction, sexual and asexual, the sexual species will eventually dominate the local environment. This is due to asexual populations losing diversity for short-term adaptations to the environment. Roughgarden proposes a population of dandelions which fit the above description. The parental generation of a sexually reproducing species and asexually reproducing species contains equal ratios of the three genotypes (A1A1, A1A2, and A2A2). The F1 generation of the asexual dandelions will contain the same ratio as the P-generation. Conversely, following standard principles of sexual reproduction, the F1 generation will be 25% A1A1, 25% A2A2, and 50% A1A2. With the addition of differential survival related to these genotypes (certain genotypes surviving better in different degrees of sunlight), the asexual population will eventually drift toward one genotype and die off when the environment changes to suit a different genotype. The sexual population in the same situation will remain diverse enough to survive changing environments. From this theory, Roughgarden concludes that the main benefit of sexual reproduction is the maintenance of genetic diversity when compared to similar asexual populations.

The IR model of the development of anisogamy The IR model for the development of anisogamy is named after its developers Priya Iyer and Joan Roughgarden. By considering the evolution of anisogamy in hermaphroditic marine invertebrates and bisexual plants, the theory postulates of a gene locus which controls both sperm and egg size produced by an organism. Anisogamy could evolve in diploid hermaphroditic adults as an individual adaptation which increases its own fitness.

Hermaphrodism Hermaphroditic animals and dioecious plants represent a large portion of sexually reproductive species. Under social selection theory, species where individuals produce two different gametes predate strictly gonochoristic and monoecious species. Separate sexes can, therefore, be described as derivations of primal hermaphrodites. Males arising in primarily hermaphroditic species gain an advantage in certain environments as fertilizers because they lack the energy cost of producing eggs. The development of monoecious and gonochoristic species represents a transition from broadcast fertilization to localized and internal fertilization.

Simultaneous hermaphrodism exists in species with pre-Cambrian roots, and several families of organisms have shifted between hermaprodism and gonochoism over their evolutionary history. There are sequentially hermaphroditic species, such as the goby, which show bidirectional sex changing. The dwarf males of anglerfish in the family Ceratiidae function as "mobile testes" for the females of their species.

Behavioral principles

Reproductive transactions Animals help another in order to access reproductive opportunities. Any inequality in this opportunity is due to predation or resource availability. Therefore, there is value in boosting the reproductive fitness of an animal's parents or siblings, both of which share genetic information. Even without this genetic relationship, reproductive transactions can be valuable. Sexual conflict arises from a failure for pairs to negotiate value of reproductive transactions effectively. Mating can therefore serve purposes beyond reproduction, if the maintenance of social structures does not decrease effective fitness. Homosexual mating behavior is observed in species where this is the case. Several asexual species of whiptail lizards have been observed to engage in mating and pair-bonding despite the lack of gametic fusion.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Social selection

Start with the simplest possible case. Write down what Social selection claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Social selection before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Social selection ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Social selection

In research: Social selection appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Social selection in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Social selection is common in secondary-school and first-year university syllabi. It links to neighbouring topics Extended evolutionary synthesis, Sexual selection, so understanding it makes those chapters shorter.
In everyday life: Look for Social selection outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Social selection in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Social selection means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Social selection out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Social selection in simple terms?

Social selection is a term used with varying meanings in biology. Joan Roughgarden proposed a hypothesis called social selection as an alternative to sexual selection.

Why does Social selection matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Social selection?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Social selection.