This is a submission for the Anatomically Correct Series

How would you evolve a harpy?

A harpy is defined by Wikipedia as a flying creature with:

  • Long, human hair
  • Human faces
  • Feathered bodies
  • Clawed feet
  • Bird wings and (sometimes) tail

From various mythology, they appear to be able to:

  • Fly for a fairly long distance, (say a mile or two)
  • Live on Earth,
  • Eat human-digestible food
  • Speak like a scratchy-voiced human woman
  • Understand human language

There does not appear to be a discernible male of the species.

Question: How would evolution cause these creatures to come into existence?


2 Answers 2


To me, it is clear we need to start with a bird and evolve human-like features, as opposed to vice-versa. I will start with a bird whose name already implies where we are going- the harpy eagle (Harpia harpyja).

To address your definition point-by-point:

  • Human hair - The double crest of this eagle hints at hair already. If it expands and becomes rougher over time, it might certainly look like human hair.
  • Human face - As I look at pictures, its already close. If the eagle's face moves toward that of its cousins, the barn owls, it might present a human-like appearance.
  • Feathered bodies- No change needed.
  • Clawed feet - Done.
  • Wings and tail - Got it.
  • Fly - Yep.
  • Live on Earth - Check.
  • Eat human food - Ok, we humans do not normally eat sloths and monkeys, but we're capable. Also, we do eat salads, which wouldn't be good for the eagle. Going from a strict carnivore to a more opportunistic feeding habit will take several generations, but it has happened in evolution before.
  • Speak/ understand human language- Borrowing from a comment, the eagle needs to learn from parrots, ravens, and similar birds. It will begin with mimicry, and evolve into full speech.

As I score it we begin with 5-and-a-fraction out of 9, with the other 4 totally plausible given the right evolutionary pressures.

Update: What are those evolutionary pressures? In a few words- habitat change or loss. As the creature is pushed further and further out of the rain forests of Central America, it must adapt to the different habitats it encounters.

Hair: I see two possibilities, either climate or prey changes. As it expands its range, it comes into cooler zones and needs more thermal protection for its head. Alternatively, it begins eating something tougher, and needs the crest to be like a helmet- kind of the opposite of why vultures have no head feathers.

Face: Same as the owls, to better see certain prey items, focus the sounds of prey into the ears, and move more stealthily when catching prey.

Food: Its preferred foods are either absent or less easily located in the new habitats. Each generation adapts to eat a wider variety of things.

Speech: Forced into ever closer and more frequent contact with humans, it realizes the advantages of being able to trick them and steal their scraps, not unlike crows already do.


I don't see a mechanism for evolving both hair and feathers. Maybe what you take to be hair is actually long stingy feathers, or feathers that further evolved to be hair-like.

But why evolve a totally different covering on the head? Bald eagles have changed their head covering due to the way they feed. Having the environment presented to the head cause selection pressure is the general mechanism: maybe they get bits of stuff and gunk caught in it and it's advantageous to be able to comb it out, thus a simple strand rather than a complex shape.

The human jaw goes against evolution. Birds evolved beaks after flight to save weight.

The pictures also show mammalian breasts. Birds evolved different mechanisms (e.g. crop milk, or simple regurgitation) but they might have evolved the same solutions as mammals in the same way that mammals did.

There are birds that are omnivorous, understand human speech, and form human speech.

What could serve as the basis for the legend would be a flighted bird whose head became featherless (showing bare skin), eyes in a binocular arrangement, and beak retracted to leave a flat face. Perhaps the beak could be colored to resemble lips, All this would be due to the diet and manner of feeding.

The bald face would be supplanted by top-head covering that still protects against the sun but is easy to rinse out, so more stingy.

The stylized breasts in the drawings might be literal observations: circular target-like markings on the chest. These would be typical eye mimic spots to seem like a very large predator from a distance or glimpsed in the thicket. But human men got a different impression.

Now given a naked flat face that sort-of resembled a human, might it then evolve to look more like a human face as a form of mimicry? A glimpse of what might be a human face, as opposed to a deer in the woods, is enough to make a hunter hesitate before taking a shot at something that moved. Other formidable beasts might fear humans and mimicking the part that other animals notice as being distinctive (and they pay attention to the predator's eyes) would let them spook other dangerous animals that they would otherwise fall prey to.


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