SMRs and AMRs

Thursday, July 11, 2013

Mammals pick offspring’s sex to maximize number of grandchildren, study shows

By Meeri Kim, WashPost, Published: July 10

Mammals appear to have the ability to select the gender of their offspring for the benefit of their species, according to a new study that followed three generations of more than 2,300 animals from the San Diego Zoo.

It is not a conscious choice, but in some way, a female’s biology has the capability to assess her health, the quality of her mate, and her environment to determine which sex to go with, according to study author and Stanford evolutionary biologist Joseph P. Garner.

For a lioness, for example, the safest bet would be to have a girl. Even if her daughter isn’t the strongest or highest-ranking female, she will most likely have at least the average number of cubs.

Sons, on the other hand, are a high-risk but potentially high-reward bet. Most male lions don’t reproduce because they are beat out by the few alpha males that father the vast majority of cubs. With sons, she could end up with zero grandcubs, or hit the genetic jackpot.

Which direction the pendulum swings is not random but depends on exactly those factors of mother’s health, mate quality and dominance. If those swing in her favor, the researchers say, her body will bias towards having a boy.

(More here.)

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