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1 .This is Scientific American's 60-Second Science. I'm Karen Hopkin. This'll just take a minute.
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2 .Most birds don't have penises.
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3 .Good, I have your attention.
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4 .Of course female birds don't have penises, but neither do most males.
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5 .Now researchers have unraveled the genetics behind the disappearance of this anatomical apparatus.
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6 .Their penetrating insights are in the journal Current Biology.
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7 .Only 3 percent of avian species have males with obvious organs of intromission.
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8 .Ducks and other water fowl are fairly well endowed.
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9 .But most birds have just rudimentary gear, if anything at all.
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10 .To get to the root of this penile puzzle, researchers compared the embryos of chickens and ducks.
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11 .Both types of birds start to develop a member.
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12 .But in chickens, this so-called "genital tubercle" shrinks before the little guys hatch.
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13 .And it's because of a gene called Bmp4.
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14 .Bmp4 basically tells cells to commit suicide.
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15 .This form of cell death keeps birds from sprouting teeth.
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16 .And in developing male chickens, it causes the phallus to regress.
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17 .Why this happens is still a mystery.
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18 .It may allow female birds to be more selective about their mates.
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19 .Because males with external equipment tend to impose it where they will.
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20 .Whereas those without have to let the ladies rule the roost.
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21 .Thanks for the minute, for Scientific American's 60-Second Science. I'm Karen Hopkin.
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