Part 6 - Multisystem Dependence
Below is an excerpt from Revere Health that gives a very brief and general introduction into our body's multisystem dependence.
"The human body contains trillions of cells, 78 different organs and more than 60,000 miles of blood vessels if you stretched them end-to-end. Incredibly, all of these cells, vessels and organs work together to keep you alive.
Each organ belongs to one of ten human body systems. These body systems are interconnected and dependent upon one another to function. Your heart does not beat unless your brain and nervous system tell it to do so. Your skeletal system relies on the nutrients it gains from your digestive system to build strong, healthy bones.
There are 10 body systems: Circulatory, Respiratory, Nervous, Muscular, Skeletal, Digestive, Endocrine (hormones), Lymphatic (immune system), Reproductive, Integumentary (skin, hair).
A body system is a group of parts that work together to serve a common purpose. Your cardiovascular system works to circulate your blood while your respiratory system introduces oxygen into your body. Each individual body system works in conjunction with other body systems. The circulatory system is a good example of how body systems interact with each other. Your heart pumps blood through a complex network of blood vessels. When your blood circulates through your digestive system, for example, it picks up nutrients your body absorbed from your last meal. Your blood also carries oxygen inhaled by the lungs. Your circulatory system delivers oxygen and nutrients to the other cells of your body then picks up any waste products created by these cells, including carbon dioxide, and delivers these waste products to the kidneys and lungs for disposal. Meanwhile, the circulatory system carries hormones from the endocrine system, and the immune system’s white blood cells that fight off infection.
Each of your body systems relies on the others to work well. Your respiratory system relies on your circulatory system to deliver the oxygen it gathers, while the muscles of your heart cannot function without the oxygen they receive from your lungs. The bones of your skull and spine protect your brain and spinal cord, but your brain regulates the position of your bones by controlling your muscles. The circulatory system provides your brain with a constant supply of oxygen-rich blood while your brain regulates your heart rate and blood pressure.
Even seemingly unrelated body systems are connected. Your skeletal system relies on your urinary system to remove waste produced by bone cells; in return, the bones of your skeleton create structure that protects your bladder and other urinary system organs. Your circulatory system delivers oxygen-rich blood to your bones. Meanwhile, your bones are busy making new blood cells." (Revere Health, https://reverehealth.com/live-better/how-body-systems-connected/)
If today's ten body systems evolved, great specificity was required to build upon the precursors. The newly generated molecular chemistry and anatomical connections had to work into chemical inputs and outputs and anatomical structures already present in precursory systems. Furthermore, whenever one precursor system developed a dependence upon another system (as seen in every body system above), any genetic alteration in one system had to benefit (or be neutral) to the other dependent systems.
Each alteration had to simultaneously build up the complexity of one system, not disrupt the needed supply or interaction of the dependent systems, and also be measurably beneficial in increasing the organism's survival rate. The complexity of integrated systemwide changes is far more complex than the stepwise anatomical progression sometimes proposed.
In addition, the above requirements do not even begin to address the neurological control through the nerves, brain, and neurological chemistry that we observe today as the brain exerts control over the majority of the organs in these systems. The alterations that generated these new organs and each level of complexity within these organs also had to, at some time, generate and cooperate with the neurological control and connections to the brain.
Evolving Complexity
Everywhere scientists look from bacteria to humans, from organelles to organs, from cells to systems, we see vast complexity and dependence. Even in a single cell, organelles are dependent and interconnected with the other organelles. And when the organelles or organs work together, tremendous function results. The eye and uterus show that these types of functions are not general or unspecific in nature. The resulting outcomes like vision and human birth are functions so impressive that we still have not been able to fully comprehend all the mechanisms involved.
Today we often observe in people how one molecular change in a system causes malfunction. In experiments, the probability of a nonbeneficial mutational change vastly outweighs the probability of a beneficial change. Beneficial changes are rare, and even then, most beneficial changes are simply turning on or off coding that was already present in DNA.
Changes in organisms do occur; change in itself is likely. But if the change is required to be beneficial and to lead to new encoding of information, increased complexity, or a new intersystem dependence, then the number of possible changes that could happen are severely reduced. These types of changes require such extreme precision not only to add new inputs and outputs to chemical reaction sequences, but also to change independence to dependence without harming preexisting systems. These changes highly narrow the available change options at each step of evolution. Meanwhile, test data continues to demonstrate that the overwhelming majority of mutations occurring, damage function, structure and viability.
The level of complexity and dependence our bodies possess would require an untold number of iterations of specific chemically and anatomically aligned and beneficial alterations. And at each of these precursor stages, the cell or organism would have to measurably surpass its precursor stage in rate of superior survivability.
Some scientific naturalists have questioned if the stepwise changes between these sustainable life forms follows an unknown biological law. If that is in some way the case, it is noteworthy that biological laws alone did not mandate the changes. We still observe nonliving substances, prokaryotes, eukaryotes, and a vast array of plant and animal organisms in precursor type states as defined by evolution. If there are biological laws governing types of DNA and epigenetic changes, they alone do not drive all organisms to change towards the same path. Some precursors continued and now proliferate in their own precursor states. Many ancient species are alive and well today and closely resemble their prehistoric kin. Based on the vastness of organism variety, these laws don't even appear to bias the changes towards the human outcome.
If environmental or intercellular conditions plus biological laws drove the changes, then the number of times these conditions interacted with each evolutionary path is quite remarkable. There are a vast number of plant types, prokaryotes, eukaryotes, and different animal species whose molecular composition and anatomical parts are vastly different. Each different organism would need to be started in motion through some kind of interaction with environmental and intercellular conditions. Then these unknown biological laws would still have to yield such precise changes as discussed earlier to build up evolutionary lines while also working within the limits of chemical cascades, anatomical structures, and system interdependence.
Today we observe changes caused by biological events. However, beneficial changes caused by biological events which result in an increase in complexity, information, and/or dependence, is extremely rare. And the quantity of iterations of beneficial changes needed to produce the human body would have to parallel the complexity and dependence present today. This would require a multitude of multiplications of very unlikely events.
For a thought experiment, we could assume there were/are several biological laws that drove evolutionary changes in discrete sets. We could even assume for this experiment that the changes occurred in such large sets so that each organism alive today is the direct result of one change set acting upon another stably reproducing organism alive or fossilized today. In other words, we could assume that biological laws drove change sets so large that biological forms jumped in evolutionary steps from cells and species we observe today (living or fossilized) to other cells and species we observe today. Then we could consider how many sets of changes must be generated by environmental and intercellular conditions interacting with biological laws to yield every living organism today.
Every single-celled microorganism, every type of organelle, every kind of plant cell, every kind of animal cell, and also every varying tissue, organ, system, chemical cascade, and developed dependence found in every distinct organism would have to be generated. To begin investigating what this entails, we could examine what types of formations must have been generated to result in one of the first living organisms on earth, bacteria.
The typical Gram-positive bacterial cell has several interesting components. These bacteria have a protective cell wall with a semipermeable membrane which is used for transporting molecules, cell signaling, generating energy, synthesizing enzymes, excreting toxins, and cell growth. They have cytoplasm with DNA that codes for its proteins, functions, controls, and reproduction. They also have organelles called ribosomes that manufacture the proteins encoded in DNA.
Gram-positive bacteria have another organelle called a flagellum that uses anatomical parts and chemical reactions for mechanized movement. They also have pili which are hair-like appendages that allow it to stick to surfaces and transfer genetic material. Depending on the kind, they also have either a mechanism or chemical pathway for feeding.
This brief description can make these parts appear simple. Taking a deeper look into one of bacteria's organelles, the flagellum, reveals quite a marvel! In the article found at https://www.ncbi.nlm.nih.gov/books/NBK6250/, The National Library of Medicine describes the flagellum as "a biological macromolecular nanomachine for locomotion." In twelve pages of details, this article describes the molecular makeup of the flagellum's parts and the techniques these molecules use for assembly. The diagram seen at https://www.ncbi.nlm.nih.gov/books/NBK6250/figure/A75343/?report=objectonly shows the 20 different structural parts of this machine that must be assembled through points of stability and instability in a precise order.
Once again, this mechanical marvel is not functional simply because of the presence of the proteins used in its assembly. Along with the structural components, a whole regulation package must be present to make this organelle beneficial to the organism. In an article on flagellum (https://www.biologyonline.com/dictionary/flagellum), Biology Online describes five of the regulatory mechanisms that work with the flagellum. Some of these regulators control the assembly of the flagella through activating or repressing genes or interacting with RNA. Others involve the transportation of flagellar components and interactions that result in anchoring these components. Different regulators allow the organism to use the flagellum to respond to its environment through chemical gradient response. Depending on the type of bacteria, other regulators are present which assist in the additional functions specific to the additional roles flagellum can play.
A study of bacteria shows that the generation of these basic precursors was far from basic. The anatomic requirements are precise and complex, and are assembled with regulators. The resulting structures (like the flagellum and cell membrane) have remarkable function and respond in chemical reactions to sustain the life of the organism. Beyond these features, a study into what is required molecularly for one bacteria cell to divide (reproduction) can be found at the National Library of Medicine article, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7157936/. DNA copying and cell division is far from a simple process.
This glimpse into bacteria shows that even bacteria are not a simple step from nonliving chemicals. Bacteria are complex and coordinated machines. Therefore, even the generation of the components of bacteria are involved incredibly unlikely events.
In Part 7 we will take a look into another fascinating system of the human body, the immune system.