All of the Patristic writers of the Church lived in what we would call the “pre-scientifc” age. Sometimes that adjective “pre-scientific” is used in a pejorative sense, implying that even the wisest of people in those days were superstitious or scientifically ignorant. However, many of the Patristic writers were among the educated and intellectuals of their day and had an acute interest in science – at least as science was understood in their day. They did not try to promote ignorance and superstition and in fact exposed fraudulent religion as encouraged people to become enlightened with the best knowledge available to them.
Because they were good observers of nature, they also occasionally touch upon an idea that while having a different meaning in their day comes close to ideas that we now hold through scientific inquiry rather than seeing them as revealed by God. So we can read from the National Institutes of Health a description/definition of stem cells.
“Stem cells are important for living organisms for many reasons. In the 3- to 5-day-old embryo, called a blastocyst, the inner cells give rise to the entire body of the organism, including all of the many specialized cell types and organs such as the heart, lung, skin, sperm, eggs and other tissues. In some adult tissues, such as bone marrow, muscle, and brain, discrete populations of adult stem cells generate replacements for cells that are lost through normal wear and tear, injury, or disease.” (NIH, “What are stem cells and why are they important?”)
Stem cells are involved in the formation of specialized cells, body parts and organs within an organism, and also account for the differences in organs and body parts between species.
With that explanation of stem cells in mind, it is interesting to compare it with a thought from St. Irenaeus, who died in 202AD and so was really a 2nd Century writer. He’s writing on the development of a human’s body. He knows nothing about stem cells, and yet describes the miracle of how various body parts and organs form. He gives glory to God for this miracle but is also giving recognition to a process which can be observed in nature.
“And that flesh shall also be found fit for and capable of receiving the power of God, which at the beginning received the skillful touches of God; so that one part became the eye for seeing; another, the ear for hearing; another, the hand for feeling and working; another, the sinews stretched out everywhere, and holding the limbs together; another, arteries and veins, passages for the blood and the air; another, the various internal organs; another, the blood, which is the bond of union between soul and body. But why go [on in this strain]? Numbers would fail to express the multiplicity of parts in the human frame, which was made in no other way than by the great wisdom of God. But those things which partake of the skill and wisdom of God, do also partake of His power.” (Against Heresies and Fragments, Kindle Loc. 7508-13)
For St. Irenaeus, the development of the parts and organs of a human body are really the work of the wisdom and power of God. Obviously for him, this development of a human being does not unfold according to random processes, but according to a plan. Organization and an organism emerge from material that is physical. It is a movement against entropy and toward meaning and design. Although nature moves towards entropy, chaos, disintegration, reproduction and genetics pushes towards organization, purpose and meaning.