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A team of researchers led by Christine Drea, professor of Evolutionary Anthropology at Duke University, has shown that testosterone-fueled aggression in female meerkats may have played a crucial part in the evolution of cooperation in meerkat societies.

Meerkats are social mammals that live in small to medium-sized groups in arid environments in southern Africa. A single dominant matriarch rules the group and is assisted in rearing her pups by the subordinate members. Meerkat parents cannot raise offspring on their own as they need the help of others to find food for the pups and protect them while the adults are off foraging.

The research team worked with 22 clans of meerkats that live in the Kuruman River Reserve, in South Africa’s Kalahari Desert. These meerkats have been the subjects of numerous scientific studies, over decades, and are habituated to the presence of humans. Researchers were able to observe the behavior of the matriarchs during their pregnancies, and to note instances of aggression. They also collected samples of blood and feces from individuals to measure testosterone levels.

Observations showed that matriarchs do not lead their groups by being kind or nice. They dominate by pushing, shoving, and biting the subordinates, and mark their territories with a pungent substance secreted from glands under their tails. If any subordinate females do become pregnant, a matriarch may expel them from the group or kill their new-born pups.

https://www.nature.com/articles/s41467-021-27496-x

Female intrasexual competition can be intense in cooperatively breeding species, with some dominant breeders (matriarchs) limiting reproduction in subordinates via aggression, eviction or infanticide. In males, such tendencies bidirectionally link to testosterone, but in females, there has been little systematic investigation of androgen-mediated behaviour within and across generations. In 22 clans of wild meerkats (Suricata suricatta), we show that matriarchs 1) express peak androgen concentrations during late gestation, 2) when displaying peak feeding competition, dominance behaviour, and evictions, and 3) relative to subordinates, produce offspring that are more aggressive in early development. Late-gestation antiandrogen treatment of matriarchs 4) specifically reduces dominance behaviour, is associated with infrequent evictions, decreases social centrality within the clan, 5) increases aggression in cohabiting subordinate dams, and 6) reduces offspring aggression. These effects implicate androgen-mediated aggression in the operation of female sexual selection, and intergenerational transmission of masculinised phenotypes in the evolution of meerkat cooperative breeding.

From watching Meerkat Manor, I was surprised by how brutal they can be.

Me too. I felt particularly sorry for one who was expelled from her colony after getting pregnant. They're such adorable creatures yet so vicious.

Just imagine if humans had this type of matriarchy.

My little fun unlikely unscientific theory is that if males get really aggressive, and there will be social pressure / sexual selection that will force females to match the males with similar aggression.

In many animals females counter male aggression with other methods, but there has to some situation that forces females to have no other choice, but with violence. Which could over many ten thousands of years make more females more aggressive, and sexual dimorphism changes.