How do we know the doctrine of 'after his kind' is true?

The doctrine is substantiated by its frequent mention in Scripture, particularly in Genesis 1, where God explicitly states that every creature produces after its own kind. This consistent declaration across various aspects of creation demonstrates a divine principle set by God. Furthermore, Christ reaffirms this order in the New Testament when He speaks about spiritual birth, confirming that flesh gives birth to flesh and spirit to spirit. The integrity of this doctrine is supported by both Old and New Testament teachings, establishing its truth in the Christian worldview.