Biologists studying mammals at the San Diego Zoo say expectant moms have the ability to choose whether to have a boy or a girl.
But there's a catch. They say it's not a conscious decision.
Researchers say the female body subconsciously factors in a host of environmental and societal factors and then just makes the call.
They also say there's no question that humans do this, they just don't know exactly how.
To read more details from the study, click here.