Rick presented a study in the Week 2 lecture "Sperm Wars" that investigated the efficacy of the human penis as a sperm displacement device. How did the researchers conduct their experiment?

Question

BlackTom AI · Accepted Answer

Three differently shaped artificial penises, an artificial vaginal tract, and an artificial semen substitute were used to simulate intercourse and measure sperm displacement.

1. Relevant knowledge points and concepts
- Sperm competition theory predicts adaptations that increase a male’s chances of fertilization when females mate with multiple males. One hypothesized adaptation is that penile morphology (e.g., the coronal ridge) can displace rival semen from the vaginal canal. Experimental tests of this idea use controlled, repeatable simulations rather than invasive tests on humans.

2. Step-by-step reasoning and experimental procedure
- Researchers constructed three artificial penis models that differed in shape (to represent morphological variation thought to affect displacement).
- They created an artificial vaginal canal and a semen analogue (often a dyed fluid or gel) to represent earlier ejaculate.
- The “vaginal” canal was first filled with the artificial semen to simulate prior mating.
- Each artificial penis was then inserted and moved (standardized thrusts or strokes) under controlled conditions.
- After a fixed number of thrusts, the remaining volume or location of the artificial semen was measured (e.g., amount displaced or removed from the canal).
- Comparing displacement across the three penis shapes allowed assessment of which form was most effective at removing the simulated rival semen.

3. Calculations / measurements
- Measurements involved fluid volumes or proportions displaced; the protocol standardized stroke number and measured pre- and post-test volumes to quantify percent displacement (no algebraic steps needed here beyond subtraction and division to compute percent displaced).

4. Why the correct answer is correct
- The described method (mechanical simulation with three artificial penises, an artificial vagina, and artificial semen) matches published experimental designs testing the sperm-displacement hypothesis and is exactly option (a).

5. Why other options are incorrect
- (b) describes genetic paternity analysis in humans—an observational genetic study, not the mechanical experiment presented. (c) proposes a comparative primate correlation study across species—also not the mechanical lab test. (d) wrongly adds human volunteers; the actual experiment used artificial devices, not human participants.

6. Conclusion
The experimental method matched option a: simulating sex with three artificial penises, an artificial vagina, and artificial semen; this confirms the provided correct answer (a).

Rick presented a study in the Week 2 lecture "Sperm Wars" that investigated the efficacy of the human penis as a sperm displacement device. How did the researchers conduct their experiment?Single choice

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