Glory of God
God made everything and gave authority over the earth to man by the words He spoke, it became a heavenly law. At that time there was no physical evidence of the trees and plants, animals and man, all were in the spiritual and perfect. Moreover, in the spiritual realm, God saw it and validated it. God gave plants and fruit for food, there was no need to kill, the life was forever and the earth was rich and big enough as the earth still is today.
In that progress of creation, God made man to live forever, multiply and have children, no death. Imagine how many inhabitants would be living on earth today if Adam and Eve had listened to God and not eaten of the fruit. Today the earth is under the curse, and does not function, as it would have without the sin. In spite of the vast number of people on earth, it would have been enough for all by the blessing of God.