Humanoid

Humanoids were a classification of species, which were generally bilaterally symmetrical bipeds with a naturally upright posture, two arms, two legs, one thorax, a neck and head with a brain located in it. Humanoid species were very common in the universe. (DWN: Galaxy Four)

The humanoid form made an excellent concentrated protein. (DW: Revelation of the Daleks)

The Daleks used humanoids as work machines, believing they had no other value. (DW: Destiny of the Daleks)


 * However, this was most likely due to their Dalek-centric view rather than to any other reason.

Humanoids were referred as "fleshy bipeds" by the Mantasphid Queen. (DW: The Infinite Quest)

One Rill believed that the humanoid form was poorly adapted and led to a shorter lifespan. (DWN: Galaxy Four)

Theories
One of the more popular theories as to the many humanoid species is that the evolution of Gallifreyans relatively early in the history of the universe affected a morphic field for the humanoid form that resonated across the universe and influenced the development of later species in a similar direction. (NA: Lucifer Rising)

Another implies that Rassilon seeded the early planets with biogenic molecules that would develop into humanoids, specifically ones which resembled Gallifreyans. (BFA: Zagreus)