BIOL 178 Lecture Notes - Lecture 16: Genitourinary System, Androstenedione, Globulin

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6 Mar 2020

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Lecture #16 aggression: females, have masculinized external genitalia and masculinized behavior, females are more aggressive than, and behaviorally dominant to, males, pseudoscrotum peniform clitoris through which urogenital tract passes. What are the proximate/developmental causes of heightened female aggressiveness: prenatally, high levels of androstenedione from the maternal ovaries are converted to t and may masculinize female (and male) fetuses. What is the functional significance of high prenatal androgen exposure in females: during pregnancy, dominant females have higher androgen levels than subordinate females, mothers" androgen levels during late pregnancy, predict cubs" mounting and aggressive behavior. Conclusions: high prenatal androgen levels may organize aggression in both sexes, proximate cause of sex difference in aggression (females more aggressive than males) is unclear. Inter-generational transmission of aggressive behavior may occur through non-genomic maternal effects . Intense feeding competition probably selected for high aggressiveness in female hyenas: no one knows why females evolved masculinized genitalia.

Related Questions

Spotted hyenas are an unusual species. They are extremely socialand have very complex social behavior. The females are extremelyaggressive and are dominant to the far less aggressive males.Female genitalia is extremely masculinized with no external vaginaand a hypertrophied clitoris that resembles a penis in size, shape,and the ability to become erect. They mate and give birth throughthis organ, which causes as many as 18% to die during their firstbirthing and 60% of the survivors to lose their firstbornyoung.

This is a female.
Note the pseudo-penis.

Several hypotheses have been floated as to why such a thingwould evolve. For each of these hypotheses, lay out thefollowing:

What sort of evolutionary process produced the masculinizedgenitalia?
What evidence would you need to support/refute thathypothesis?

Hypotheses:

Mimicry: Females are using these masculine genitalia to mimicthe submission rituals of the males.

Anti-Infanticide: Females are aggressive as a countermeasure tomale infanticide (males killing infants). The aggressiveness iscaused by increased androgens (male sex hormones like testosterone)in the females, which in turn causes masculinized genitalia.

Competition: Dominant females produce more cubs and her cubshave a strong advantage in access to meat. The aggressiveness iscaused by increased androgens (male sex hormones like testosterone)in the females, which in turn causes masculinized genitalia.

blackgoat151

Spotted hyenas are an unusualspecies. They are extremely social and have very complex socialbehavior. The females are extremely aggressive and are dominant tothe far less aggressive males. Female genitalia is extremelymasculinized with no external vagina and a hypertrophied clitoristhat resembles a penis in size, shape, and the ability to becomeerect. They mate and give birth through this organ, which causes asmany as 18% to die during their first birthing and 60% of the survivors to lose theirfirstborn young.

This is a female.
Note the pseudo-penis.

Several hypotheses have been floated as to why such a thingwould evolve. For each of these hypotheses, lay out thefollowing:

What sort of evolutionary process produced the masculinizedgenitalia?
What evidence would you need to support/refute thathypothesis?

Hypotheses:

Mimicry: Females are using these masculine genitalia to mimicthe submission rituals of the males.

Anti-Infanticide: Females are aggressive as a countermeasure tomale infanticide (males killing infants). The aggressiveness iscaused by increased androgens (male sex hormones like testosterone)in the females, which in turn causes masculinized genitalia.

Competition: Dominant females produce more cubs and her cubshave a strong advantage in access to meat. The aggressiveness iscaused by increased androgens (male sex hormones like testosterone)in the females, which in turn causes masculinized genitalia.

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BIOL 178 Lecture Notes - Lecture 16: Genitourinary System, Androstenedione, Globulin

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