I'm worldbuilding a human inspired species where females are larger than males. According to the explanations I've read about why that would happen with birds of prey, dimorphism comes from:
Avoiding to compete with each other for the same type of prey - larger females hunt larger prey, males hunt smaller prey.
Males are primary
breadprey-winners, with smaller prey being more abundant, while females do more offspring nurturing.
Larger females evolved due to larger females being better at protecting the
(Questionable) A ZW sex determination system in which males are the homo-gametic sex ZZ, while females are the hetero-gametic sex ZW. So if a beneficial mutation appears on the W chromosome it can't spread as rapidly as in the XY system, Genghis Khan-way, because females are limited to how many children they could bear (the same as humans).
(Questionable) Larger females could bear larger children that have a fitness advantage over smaller females.
Due to the above reasons, "ZW humans" developed a culture where smaller males were preferred and in which it was the females' job to protect the settlement and occasionally hunt some large prey.
Does my dimorphism explanation makes sense from a biological point of view?
My species have live birth like mammals - they don't lay eggs.
The Evolution of Reversed Sexual Dimorphism in Owls: An Empirical Analysis of Possible Selective Factors proposes 20 different reasons as to why females are bigger:
- Egg size.
Large females can lay larger eggs than smaller individuals.
- Follicle protection.
Larger females provide a better cushion for developing eggs than smaller ones.
- Breeding increment in weight.
Females of many species increase in weight prior to egg laying.
Larger females incubate more efficiently than smaller individuals.
- Nest protection.
Larger females are more effective in deterring predators than smaller individuals.
- Territorial defense.
Small, agile males are better in the aerial defense of territory against conspecifics than larger, less agile individuals.
- Feeding efficiency.
Larger females are more efficient at dismembering prey and feeding bits to small young.
- Foraging interference.
It is more efficient for only one member of the pair to hunt alert and agile prey than to have two birds moving about alerting prey and thus interfering with each other.
- Energy conservation.
Energy consumption is a function of body size, thus small males might forage and provide food for the young more efficiently than large females.
- Pyramid of numbers of prey sizes.
Small prey are more abundant than large prey, and small males should do most of the hunting until the food demands of the young become sufficiently great, and the supply of small prey sufficiently depleted, at which time the female must join in hunting, capturing, and delivering larger prey.
Coloniality may inhibit the evolution of RSD.
Large females prevent small males, who are presumed to have less of a "parental instinct," from eating their young.
Formation and maintenance of pair-bonds is facilitated by female dominance, and large size facilitates dominance.
Female dominance excludes the male from incubation, brooding, etc., and forces him into the role of provider of food.
- Female selection of males who are good provisioners.
Male raptors begin to provision females well in advance of egg laying.