A common feature in fantasy are half-human creatures such as centaurs, satyrs and merpeople. As much as the worldbuilding community wants these to be real, the evolution and anatomy don't match.
Centaurs; can't graze without bending down, removing the horses' advantage of running away whenever it needs to. Satyrs; the digitigrade legs can't realistically evolve in a bipedal matter, the purpose of digitigrade legs is to provide a quadruped with faster sprint speed at the cost of balance, hence needing to be quadruped. Merpeople; the classical merperson lacks the form to serve its functions, it is not fast enough under water to survive efficiently enough to evolve sapience. Half humanity is to complex to work, never mind being able to interbreed with humans.
A Possible Solution?
What if we simply lower our standards? How animalistic can I make a sub species of human without; (A) making them a separate species and (B) making them non-interbreedable with humans? How could they evolve? The features I need to evolve are:
- Markings, like a tiger except they are simply lines of melanin marking the skin along the arms and legs.
- Enlarged irises, Around twice the circumference of our irises
- Pointed ears, like the stereotypical elf
- Longer canines (keyword: not sharper but longer)
Edit Their offspring does not need to be fertile, they can be sterile (like horses and donkeys)