Learn English – Can’t think of a good word or term to describe not feeling or thinking

single-word-requests

I'm looking for a word or a term that describes a human who actually can't think. More specifically I'm thinking of a word that describes how embryos don't feel anything or think, etc.
Thanks.

For instance:

An embryo hasn't developed _________. An embryo is ________.

Best Answer

An embryo hasn't yet developed sentience.

sentient condition or character; capacity for sensation or feeling.