Part 5 - The Human Reproductive System
According to scientific naturalism, every biological system, with each of its anatomical structures and coordinating chemical pathways, must have evolved from a limited set of chemicals into the systems we observe today. The evolutionary step changes eventually generated and developed the human body with its complex chemical, anatomical, and multisystem dependence. An example of complex, system-wide dependence in the human body is the human reproductive system.
Today, two completely different and complementary sets of reproductive organs are present in humans. A look into the human male and female reproductive systems shows they are vastly complex. Each produces one of the complementary reproductive cell kinds (eggs or sperm) which have different structures, organelles, and chemistries. The egg and sperm differ in how and when they are manufactured, in the organs which house them, and in their timing and methods of distribution. And yet, though they are so different, a look into the molecular chemistry required for fertilization shows how perfectly the two reproductive cells work together.
The male and female organs allow for the sperm and egg to unite in a protected environment within the female body. While the complementary anatomies behind this delivery had to evolve (which is far from simple), what is even more astonishing to me, is the molecular chemistry required for the sperm to travel to and unite with the female egg. The article by the National Library of Medicine at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5029953/ delineates the molecular chemistry involved in the changes to the sperm once it enters the vagina to the point of fertilization. Such molecular complexity is required today that it takes eight pages to describe what must happen to the already delivered sperm cell for fertilization to occur.
The journey to fertilization, is just the beginning. Once the egg is fertilized, it must be transported out of the fallopian tube. This requires multiple inputs from the endocrine system, the autonomic nervous system, and the embryo itself. Different types of uterine cells respond with ciliary action, muscular contraction, and tubal fluid secretion which all operate in unison to move the fertilized egg in the first few days.
The National Library of Medicine article at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4171403/ gives an overview of the cell types, cell functions, and anatomical structures of the uterus. There are pages on this website just looking into molecular chemistry of the ciliary structure, motion, and regulation of the ciliary beat frequency. This article helps to show that the presence of the anatomical structures for transport are not enough; each of the molecules required in each of the chemical cascades must also be present to drive the structures and coordinate the system.
Now the process of implantation begins. To see just a portion of the molecular chemistry required during these next few days of embryo survival, see the National Library of Medicine article found at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5769129/.
The process of embryo development has only just begun. Immense anatomical, physiological, and chemical changes are initiated to start growing the placenta. To see the changes that occur in cell structure and the development of new cell types which are required in the newly forming placenta, read the section of the Science Direct article titled "Placenta Development" at https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/placenta-development. Note that this article only details the observed changes, but does not describe the molecular chemistry required to drive and accomplish each of these changes.
The placenta forms vascular connections necessary for nutrient transport which depends on the mother's digestive and circulatory systems. In addition, the placenta redirects maternal endocrine, immune, and metabolic functions to the embryo. These complex activities are sensitive to disruption, and any disruption results in a significant rate of spontaneous abortion.
Section 3 of the National Library of Medicine article found at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4303845/ gives a look into some of the different methods of transporting various types of nutrients from the mother to the fetus. Different classes of amino acids require different chemical transport systems. These transportation methods change at different times based on the requirements of the fetus. Changes in fetal oxygenation is also discussed in this article.
The National Library of Medicine article found at https://royalsocietypublishing.org/doi/10.1098/rsfs.2019.0019 gives a look into what is required for maternal blood to perfuse the placenta. And this process changes into a different process at just the right time to meet the growing fetus' needs.
The National Library of Medicine article at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7416543/ explains how the different biologic systems of the mother change during pregnancy and then return to normal after pregnancy. These biological changes in the mother for sustaining life support to the fetus are systemwide and do not even include the changes in the circulatory system for differing placental blood perfusion methods.
All of these processes must then culminate in the orchestrated finale of birth that is dependent upon the endocrine system, muscular system, nervous system, circulatory system, and even the skeletal system as the female hip structure is different from the males and allows for the birth passage of the fully grown fetus. After reading the above listed articles, I am completely amazed at the process of human reproduction. It is incredibly intricate in detail and timing, dependent upon multiple systems for control and supplies, and forms an immensely vast integration of complex anatomical and chemical steps.
Some evolutionists have suggested that inflammation around a primitive embryo mutated into a placenta over time. If that is the case, then the molecular chemistry in each of the articles cited above shows that this process of uterine fertilization and implantation, with placental oxygenation and nutritional, immunological, and endocrine support, required a monumental increase in complexity and interdependence from its beginning state of mere inflammation.
Uterine Reproduction in Evolution
A fundamental necessity of evolution is reproduction. Assuming a nonliving substance generated into a living substance, that primitive living substance would be required to reproduce itself. The generation of its anatomical and molecular chemical structure must also have been accompanied by the generation of a method of reproduction; otherwise, this first new substance would have been the end of the story. For any living organism, cell or species, to participate in an evolutionary chain, it must be successful in reproduction or else that new cell or species would have discontinued after one generation.
The method of human uterine reproduction described above is markedly complex and interdependent; it is evident that this method of reproduction has evolved numerous times over. The reproductive system's evolution had to be fully functional at each stepwise change in order to achieve species propagation. Each stepwise change also had to be measurably more beneficial than the method preceding it; otherwise, the change in the reproduction system would not become widespread.
According to evolution, at some point a system of reproduction began which utilized a form of uterus and placenta. Since all humans have the same type of uterine reproductive system, every stepwise precursor system was ultimately replaced somewhere in the evolutionary path to today's human body. Each evolutionary change began in one generation, and had time over multiple generations for its offspring to infiltrate all the population that would continue in the pathway to our present-day human body. The number of times this occurred has to be comparable in some way to the vastness of the anatomical and chemical complexity in our uterine reproduction.
It must be noted that many of the events in uterine reproduction depend on other body systems. The viability of the embryo is incredibly sensitive to all of these required systems' anatomical and chemical pathways mentioned in the articles above. Because of this, today's rate of viable pregnancies is only 74%; doctors estimate that 26% of pregnancies end in miscarriages.
One reason for such a high rate of miscarriages is that today's human uterine reproductive system does not have overlapping components. The dependence on multiple body systems introduces potential points of reproductive failure; there is no backup for each of the roles that the endocrine, muscular, nervous, circulatory, and skeletal systems play. These other body systems form a long sequence of parts that each have independent points of failure. These body systems must generate needed molecular supplies, and also be perfectly coordinated in the timing of the delivery of these supplies.
According to evolution, the developmental path of our uterine reproduction system started with an already capable and effective method of reproduction. Then multiple times over, DNA changes introduced complexity, dependence, and points of failure, while simultaneously increasing species survival rate. To begin to grasp what this would mean, we could compare bacterial reproduction to human uterine reproduction, and list all the additional elements found in our reproductive system.
Every cell type and chemical cascade on this list, found in the human reproductive organs and in other body systems involved in the process, would have to be stepwise generated, with time for generations to grow and pass on their genes sufficiently to infiltrate the population. In addition, the simultaneous evolutionary alterations in other body systems must have resulted not only in their own beneficial functions, but also in cooperation with the needs and timing of the evolving reproductive system.
These stepwise alterations apply to more than just anatomical structures. As we saw earlier in this section, not only are the male reproductive organs required to produce and deliver the sperm, there are eight pages of chemistry required to move the sperm through the female organs and facilitate it uniting with an egg.
The first-time our reproductive system was dependent on a sperm and an egg, these two cells had to be able to unite. The chemistry required to accomplish this uniting had to evolve simultaneously with the development of the sperm and the egg. This magnifies the required elements of stepwise evolution.
And this requirement of both anatomical structures as well as elaborate accompanying chemical cascades is found over and over in the nine-month process of embryonic and fetal development. Therefore, this study has led me to ask: Could there be enough time to start with the reproduction system of bacteria, and over time, generate the anatomical and chemical complexity and multiple system dependence which we see in the human reproductive system? The number of chemical pathways listed in the articles above is mind blowing, and the molecules required in these reactions depend on multiple body systems for delivery.
Since the human reproductive system is not the only system in the body that depends on multiple systems, in Part 6 we will take a closer look at our body's ten main systems.