When I read this question it make me think of the philosophical question of "why didn't God just simply make us perfect?" As a member of The Church of Jesus Christ of Latter-day Saints, I have found my answer to this in the revelations given to the Prophet Joseph Smith. Some argue that God is all powerful, all knowing, and all loving and so the problem of evil comes about if God has the power to do anything imaginable, and knows how to do anything imaginable, and loves everyone as one of his children. One must ask, "why didn't God just simply make us perfect if he had the power and knowledge to do so and loves us dearly?" What I have learned from the revelations of the Prophet Joseph Smith is that God is not all powerful in that he can absolutely anything imaginable but that he is all powerful in that he can do all that is possible. Here are few passages from LDS scripture that have taught me this truth:
Doctrine and Covenants 93:29,33
29 Man was also in the beginning with God. Intelligence, or the light of truth, was not created or made, neither indeed can be.
33 For man is spirit. The elements are eternal, and spirit and element, inseparably connected, receive a fulness of joy;
From these verses I have come to understand that there is a part of man that has always existed. This part of man is known as his intelligence. If man in eternal in nature as an intelligence and has always existed, then God could not create our intelligence. If God could not create our intelligence then he could not create it to be perfect! I also learn that the elements are eternal and God did create them or us out of nothing. Our intelligence and the elements from which we were created have always existed. So if we were created from things that have always existed, then God could not create us to be perfect. Because of this truth, in order for God to have us progress to a higher state of being, we need needed to learn greater truth than we already possessed. One of the purposes of coming to this temporary mortal world was to learn and experience the difference between good and evil. As imperfect beings it was God's plan that we learn the difference between good and evil in this fallen world. When Adam and Eve fell, this is what God had to say:
Genesis 3:22
22 And the Lord God said, Behold, the man is become as one of us, to know good and evil: and now, lest he put forth his hand, and take also of the tree of life, and eat, and live for ever:
Here we see that man had advanced to become as one of the Gods, by coming to know good and evil.
The intelligences of mankind that are self-existent were given spirit bodies before being born into this fallen world. Our spirits are literally the offspring of God. God then put Adam's spirit into his physical body which was made from the dust of the earth.
Doctrine and Covenants 131:7-8
7 There is no such thing as immaterial matter. All spirit is matter, but it is more fine or pure, and can only be discerned by purer eyes;
8 We cannot see it; but when our bodies are purified we shall see that it is all matter.
Acts 17:28-29
28 For in him we live, and move, and have our being; as certain also of your own poets have said, For we are also his offspring.
29 Forasmuch then as we are the offspring of God, we ought not to think that the Godhead is like unto
gold, or silver, or stone, graven by art and man’s device.
Hebrews 12:9
9 Furthermore we have had fathers of our flesh which corrected us, and we gave them reverence: shall we not much rather be in subjection unto the Father of spirits, and live?
Because God could not create us to be perfect, we come into this world as imperfect beings to learn good and evil and are given free will to choose between good and evil. If we were not given free will, mankind could not progress of their own free will. If we were to be forced to do good we would truly be good beings in and of ourselves but we only be robots. Free will is critical in become good beings in and of ourselves. However, in this temporary mortal life, given free will, we also can choose evil. God knew that we all would fall short of perfection and sin at times. For this reason he provided a mean whereby we could be forgiven if we would repent turn away from sin. This means was the atoning sacrifice of Jesus Christ our Savior.
So in answer to the question, "are humans essentially good or evil?", my reply would be that we are imperfect being that are given the opportunity to progress to be more perfect beings by learning good and evil and choosing the good over the evil. Being imperfect beings and being tempted often to do evil, it is critical for our progression to learn the good and hold fast to it and to repent of our evil ways and seek forgiveness of our sins through our Lord and Savior Jesus Christ. We all need to be converted to Jesus Christ and become one of his disciples and learn to overcome the world following his way. Jesus is the way, the truth, and the light.
As little children born into this world we are innocent. The atonement of Jesus Christ covers the original sin of Adam and Eve and we are only held accountable for our own individual sins. Our spirits volunteered to come to a fallen temporary existence so that we could progress to become more like God. It is basically our choices in this life that determine what manner of mankind we choose to become. Let us all turn unto Jesus Christ our Lord and Savior and become what we all desired to become before we were born into this fallen world.