A human being is not just a physical body but a composite of a created spiritual soul and body. So, as others have noted, the eternal Son of God assumed a created spiritual soul with a created intellect and will which animates a body, the two irreducible components that constitute a human being and human nature, namely, a spiritual human soul and body. The eternal Son of God did not assume a human person however. Jesus is a divine person, the second person of the Trinity, in a male human nature.