Note on Zwingli

In Zwingli's "Clarity and Certainty of the Word of God" I came across this passage and it gave me pause. Here is the quote:
What it does say is this: "And God said, Let the earth bring forth the living creature after his kind: and it was so." And first, we see here that God commanded the earth to bring forth beasts. But in the creation of man he himself takes the earth and forms it into a man. Again, when he says "the living creature after his kind" he makes it clear that the soul of creature is its life, but only according to its kind or nature, which is transitory and perishable.
I found this to be suggestible and it has led me to speculate a little. The Genesis narrative teaches that human beings are unique, and since the text says that God commanded the earth to bring forth animals but teaches that God formed man directly it leaves open the possibility that all other creatures other than man may have their origin in nature. Given this, even if some hominids are similar to us, it may be the case that they were not human. Maybe they lacked some characteristic that made them less than imago dei. Anyway, just some speculations.

Support for this idea comes from the work of philosophers such as Roger Scruton and Raymond Tallis. Neither author is an orthodox Christian, but they make interesting observations about how human beings are different than other beings. Tallis has an exceptionally interesting theory that our thumbs make us unique, and Scruton notes that our subjective first person experience creates a world that isn't available to other creatures.