An animal is an multicellular eukaryotic organism from the kingdom Animalia. All life on earth aside from plants and algae are animals including humans.
Flamingos are born with gray feathers. They become pink over time due to their aquatic diet of organisms like shrimp and red algae which are high in pigments called carotenoids.
Studies have shown there is no single determinant of sex, gender, or sexuality. Thus, a binary distinction of “male or female” fails to describe a wide range of humans in practice.
Nettie Stevens and Edmund Beecher Wilson independently discovered the chromosomal XY sex-determination system (that males have XY and females have XX sex chromosomes).