There are around billions of nipples in the world, but only half serve a purpose in breastfeeding. Why only females, not men?
Deep in the rainforests, male Dayak fruit bats denies the nature's norm and nurse their young. This exception makes us wonder – why aren't more male mammals like us doing it?
Scientists have long debated why male mammals don't breastfeed. One theory blames uncertain paternity – males may not invest as much if they're unsure whose offspring they're raising.
But this theory doesn't explain everything. Azara's owl monkeys dads practically raise the kids, yet the moms do all the nursing. What gives?
But on the other hand, mathematicians are throwing a new theory into the mix: it's all about germs!
Breast milk is a living soup of bacteria, viruses, and other microbes. These are crucial for a baby's health, but too many can be bad.
By limiting breastfeeding to females, mammals might be acting like a "sieve," filtering out potentially harmful microbes while keeping the good ones. Two parents nursing may increase the risk.
This theory explains the owl monkeys too. Even though dads do most of the childcare, they might not breastfeed to avoid messing with the baby's developing gut bacteria.
The type and amount of microbes determine a baby's gut health. The wrong ones early on can disrupt a crucial development stage.
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